Cool YouTube suspension video, seeing that is "magic"
BTW those detailed cradle drawings you created were very helpful, when I had to "tweak" my 88 cradle back into spec.
A BIG Thank You for that.

Jim

"The instructions for the coil overs say that anti-seize compound must be smeared on the shock tube's threads before attempting to adjust them otherwise there's a risk of galling up the threads. That's going to make a mess."

Why not make yourself a custom spring compressor that fits while the shocks are on the car? That way you can adjust without the risk or the mess.

He said he'd have "spring socks" or something similar on it... but I can imagine that anti-seize + a couple thousand miles of road grit would not be friendly for turning the adjusters either.

Blooz is pretty darn meticulous. I suspect once the springs are set, he'll wipe off the excess and clean up the exposed threads. What remains under the nut will suffice for minor spring tension adjustments. No point soiling that sterile engine bay.

Thanks everyone for your comments! Time to answer a few questions:

quote Originally posted by Yarmouth Fiero: What's next?

I still have to sort out axles, make a flywheel, and buy a clutch package.

quote Originally posted by Sage: In your estimation, will the ride be as stiff, less stiff or about the same as a "normal" coil-over set up?

Since the bell crank ratio is close to 1:1, the ride stiffness should be no different than a normal coil-over set up with the same springs.

quote Originally posted by Jim88GT: Any thoughts/concerns about engine bay heat affecting shock performance?

I hadn't considered that aspect. I suppose it's possible that heat build up could affect their performance. I guess I'll have to hope that the airflow through the engine bay will be enough to keep this in check. Bear in mind that the F355 deck lid has a fairly large grill to exhaust engine heat so it's not like the shocks are going to be enclosed under the deck.

quote Originally posted by X-Body: Why not make yourself a custom spring compressor that fits while the shocks are on the car? That way you can adjust without the risk or the mess.

It turns out my concerns about having to smear anti-seize on the shock body were for nothing. I had forgotten that with the suspension in full droop, the springs only need to be compressed 0.3", which was easy enough to do by hand. So I just let the suspension droop to its lowest point, turned the adjuster all the way down the shock body, slipped the spring over the shock, reattached the end of the shock to the mount, and retightened the adjuster by hand until all the slack was taken up plus an additional 5/16". No wrenches + no anti-seize + no mess = one happy guy! (I'll need a set of wrenches only to tighten the lock nut).

quote Originally posted by Bloozberry: It turns out my concerns about having to smear anti-seize on the shock body were for nothing. I had forgotten that with the suspension in full droop, the springs only need to be compressed 0.3", which was easy enough to do by hand. So I just let the suspension droop to its lowest point, turned the adjuster all the way down the shock body, slipped the spring over the shock, reattached the end of the shock to the mount, and retightened the adjuster by hand until all the slack was taken up plus an additional 5/16". No wrenches + no anti-seize + no mess = one happy guy! (I'll need a set of wrenches only to tighten the lock nut).

I was wondering about that. I remembered that you'd designed for a small amount of preload, but I didn't remember how much. The springs on my struts are completely unloaded when the car's jacked up.

Hey Blooze, once your finished mocking up the engine, suspension, (front and rear) interior, underneath, etc.
will you be dipping this frame or painting all black and use sealer in the joints like factory cars are done??

Since all the effort, work, and time going into this built, I guess the last thing you want is to worry about rust.

Any plans yet??

Good work because this is really a "custom" build. A first I've seen on PFF.

------------------
fierogt28

88 GT, Loaded, 5-speed.
88 GT, 5-speed. Beechwood interior, All original.

I have just about read your whole article. I have been up nights just thinking about your build. Really great by the way. You give us so much to think about. I also want to put a Northstar in my 1984 Enterra. One thing I missed was how you mated the F40 to the Northstar. Stuff like flywheel, clutch used, things like that. What I would give to have you as my neighbor. Would Canada bust my balls if you helped me with my car? Doesn't hurt to ask. Anyways love your page and build. By the way I am a master goldsmith with the last name of Tiffany. I have a nice store in southern Idaho. Just thought we might put our love of our cars to good use. I know I could make you wife a very happy girl if we could work something out. That should earn you some bonus points mate. Let me know what you think?

Wow and wow. You guys make my head hurt. It is unbelievable what is being shared here on this thread. The whole thread is absolutely inspirational and of great help to most of us fiero build dreamers. Blooze, I mean it dude, you are something else. Which brings me to this.

I asked you once in a round about way.....does the f40 bolt right up to the N*?
Also what is your opinion on the available suspensions out there like held? Are they any better than stock suspension with upgrade shocks and struts? Don't get me wrong I think your system your working out is 10 tens. Just would like to know how you would go if your not a welder/fabricator.

Thanks again for all your sweat, blood, and possible tears. Love this thread.

------------------
Diamond Dave

84 Enterra the only one
88 Formula

quote Originally posted by fierogt28: Once your finished mocking up the engine, suspension, (front and rear) interior, underneath, etc. Will you be dipping this frame or painting all black and use sealer in the joints like factory cars are done??

Thanks fierogt28! I don't have the means locally to "dip" the frame, so it'll be seam sealed and painted. I haven't decided what colour it's going to be yet but probably a metallic gray.

quote Originally posted by Diamond Dave: ...it looked like the tranny mounted right up. Is this at least a right assumption?

First, thanks for the shower of compliments Dave. I hope you decide to stuff that Enterra's engine bay with a Northstar... it'll be a killer! To get to some of your questions, the F40 six speed does indeed have the same bell housing bolt pattern as the Northstar except for one bolt, which I made an adapter for. The other thing of course is that you have to notch one of the bell housing's internal webs to clear the Northstar starter. Otherwise it just bolts up.

quote Originally posted by Diamond Dave: Just read back a couple of posts and saw your post stating you hadn't worked out clutch, flywheel, and axels.

True, but these are simple problems to sort out... there are many people who have come up with various solutions to these issues right here on PFF. The plan for the axles is to use the inner tripot joints and axle from one car, and the outer CV joints from the Fiero. Since the number of splines for the CV joint won't likely mate up with the Fiero CV joint, the trick is to find a car with axles that are long enough to have them shortened and re-splined for the Fiero CV joints. That's what I'm researching now.

As for the clutch and flywheel, several guys have also worked out good solutions including Fieroguru who mated an F40 to an LS engine (he had a completely new flywheel of his own design machined from billet), and there's Zac88GT who used an off-the-shelf Spec flywheel and made a billet aluminum spacer plate with an aftermarket steel facing bolted to it. The choices are out there.

I've run out of time to answer your question about available off-the-shelf suspensions, but will post my opinions later.

Thanks so much for your input Blooze. It really means alot to me. I have been on track to use the N* for awhile now. Allen at chrfab pretty much helped me to stay with my dream of the N*. You and Will have solidified it. Just want to do it right. Thanks again buddy.

quote Originally posted by Bloozberry: True, but these are simple problems to sort out... there are many people who have come up with various solutions to these issues right here on PFF. The plan for the axles is to use the inner tripot joints and axle from one car, and the outer CV joints from the Fiero. Since the number of splines for the CV joint won't likely mate up with the Fiero CV joint, the trick is to find a car with axles that are long enough to have them shortened and re-splined for the Fiero CV joints. That's what I'm researching now.

Do you have axles that are the correct length? reason I ask is on my 4t80e the original builder of the car use a caddy axle on one side and smaller fiero axle on the other, with having new caddy axles and joints I could swap the parts in pic between the two different axles The cage and bearings fit both of these ,one just had a larger inner diameter to fit the larger axle but still fit the outer fiero joint fine. so I could use the smaller or larger diameter axles with the same fiero joints if I wanted. Might be worth a try if you have the outer joints that fit the axles, you could see if it would fit into the fiero outer joint.


------------------


87GTseries 1 3800sc (7.597 @88.53 1.579 60ft)
(series II swap in progress)
85GT Northstar/ 4t80e
86GT 3800 n/a
Northstar Rebuild

[This message has been edited by jb1 (edited 03-07-2014).]

quote Originally posted by jb1: Do you have axles that are the correct length? reason I ask is on my 4t80e the original builder of the car use a caddy axle on one side and smaller fiero axle on the other, with having new caddy axles and joints I could swap the parts in pic between the two different axles The cage and bearings fit both of these ,one just had a larger inner diameter to fit the larger axle but still fit the outer fiero joint fine. so I could use the smaller or larger diameter axles with the same fiero joints if I wanted. Might be worth a try if you have the outer joints that fit the axles, you could see if it would fit into the fiero outer joint.

My understanding regarding F40 axles is that the G6 axles including the center component of the outer CV joint will fit the Fiero outer CV joint "cups".

However, Blooze's car has a widened track, so he may or may not be able to use shelf axles from anything, just depending on what's available.

quote Originally posted by Will: My understanding regarding F40 axles is that the G6 axles including the center component of the outer CV joint will fit the Fiero outer CV joint "cups". However, Blooze's car has a widened track, so he may or may not be able to use shelf axles from anything, just depending on what's available.

The "star" portion from the G6 axles does indeed fit inside the Fiero Manual outer CV housing.

I think the wider track may actually help him find axles... at least on the driver side. I haven't looked at the F40 axle options in a few years, but there are more applications using the 27 spline for the transmission output now.

Looking good as always Blooze!

[This message has been edited by fieroguru (edited 03-07-2014).]

I guess I need to do mre research about what the various families of CV joints are.

As I have the A-body large hub carriers on my car, I have the larger pattern outer CV's. I @$$ume that these take the same "star" as the small pattern CV's, as they both accept the same axle shafts and the weak point of the small pattern joints is the hub spline.

However, I don't know about potential interchangeability with the XL pattern joints from a U-body van or W-body car... or maybe even Corvette.

What a frustrating and mind-boggling experience it was to research the compatibility of various axles, CV joints, and tripot joints to fit my car. I literally spent 12 hours reading through all the F40 threads here on PFF, the Cobalt SS forum, and combing through hundreds of pages on the "interparts.com" web site trying to find specific, unambiguous information about what I need to mate the F40 to the Fiero rear bearing. Don't get me wrong, there's tons of information out there but the lack of specific language to identify exactly what part is being referred to makes it impossible to follow most of the threads. And apparently I'm not alone in my frustration based on the number of posts in F40 threads, where confusion reigns. (This isn't an invitation for anyone to clutter my thread with pseudo-explanations either!)

Perhaps the reason for the confusion is that there are at least 14 variables that come into play for each axle assembly:

a. the spline count and diameter of the tripot spindle;
b. the spline count and diameter of the tripot inner spider assembly;
c. the spline count, diameter, and length of the axle rod;
d. the spline count and diameter of the CV joint spider assembly;
e. the spline count, diameter, and length of the CV joint spindle; and
f. the spline count and diameter of the wheel bearing assembly.

I gave up trying to piece various parts together when I couldn't find any specific information about bare axle rods, and when I realized that none of the complete axle assemblies that fit the F40 would be long enough for either side of my widened track. I also had a "Eureka!" moment when I ran across Zac88GT's build thread (he comes through again):

quote "The axles and intermediate shaft that I'm using (in my [Northstar] Fiero V8 swap) came from a 2005 Cobalt SS with the supercharged engine. The driver's side and passenger side axles are identical. I made my axle [rods] from a single Fiero axle [since the Cobalt SS axle rods were too short for my car]. The original Getrag passenger side axle is long enough that both new shafts can be made out of this one piece and the diameter is sufficient enough to re-machine splines on for the cobalt inner cv tripot. The axles turned out beautifully and it only cost $190 to get them both re-splined. My axles are holding up just fine and my motor is producing about 390hp and 365 ftlbs of torque at the flywheel."

So, for $155 for a new (not reman) Cobalt SS axle assembly, I can replace the axle rod with a Fiero manual transmission passenger side axle cut to whatever length I want (can't use an automatic transmission axle because they're smaller dia), have the tripot end of the rod re-splined to fit the Cobalt SS tripot spider assembly, and be done with it for a total of about $250 per axle assembly. It'll also be stronger than the Cobalt SS axle since it's about 0.100" thicker. That's all I needed to know to order my Cobalt SS axle assemblies today... they'll be here tomorrow.

In the mean time, I needed to extract some long Fiero axle rods from a couple worn out assemblies collecting cobwebs and rust in my shop's attic. (I knew they'd come in handy some day!) I'll need two of them since my project car's widened track will need a combined LH & RH axle rod length that exceeds the length of one Fiero axle. So here's a whack of pictures to show how to strip down a Fiero axle.

I started at the outer joint (CV) so I could rid myself of the dead-weight knuckle that had fused itself permanently onto the CV joint's spindle (good thing I don't need the CV joint!). First I snipped off both boot clamps:



Pulled back the boot to reveal surprisingly nice looking grease:



Then fished around for the retaining ring. In case anyone reading this hasn't done it before, you need to get your snap ring pliers inside the two tangs and pry them open, not squeeze them together.



While holding the two ends of the snap ring apart, the axle rod should just slip out of the spider assembly, and the retaining ring will stay behind with the CV joint:



Here's a close up of the CV end of the axle rod once the grease has been cleaned off.



The manual transmission axle rods have 1.063" diameters...



...there are 32 splines and the spline max diameter is 1.024":



For comparison's sake, the Fiero automatic transmission axle rods only have 29 splines vs 32 and are 0.935" diameter with max spline diameter = 0.925".

Next up: removing the tripot joint from the other end.

When I built my axles, I found a lot of cars used the 1.063" dia axle with the 1.024" 32 spline count. The 03 Chrysler 300 had 'em, a lot of GM cars used them, even Ford. I just wandered through the pick and pull with a digital calipers and measured axles until I found the length with the dia I needed. My axle shafts are made from a 99 Buick LeSabre and a 97 Ford Windstar van. Even the stub dia was the same on the tripod joints, I have '03 Chrysler rollers on '02 Caviler joints running inside Chrysler cups. You may find an existing axle without having to custom make something. I have under $100 into my axles. https://www.fiero.nl/forum/F...3/HTML/000139-4.html

quote Originally posted by Bloozberry: What a frustrating and mind-boggling experience it was to research the compatibility of various axles, CV joints, and tripot joints to fit my car.

That's been my experience also.

quote Originally posted by Bloozberry: I also had a "Eureka!" moment when I ran across Zac88GT's build thread (he comes through again):

quote "The axles and intermediate shaft that I'm using (in my [Northstar] Fiero V8 swap) came from a 2005 Cobalt SS with the supercharged engine. The driver's side and passenger side axles are identical. I made my axle [rods] from a single Fiero axle [since the Cobalt SS axle rods were too short for my car]. The original Getrag passenger side axle is long enough that both new shafts can be made out of this one piece and the diameter is sufficient enough to re-machine splines on for the cobalt inner cv tripot. The axles turned out beautifully and it only cost $190 to get them both re-splined. My axles are holding up just fine and my motor is producing about 390hp and 365 ftlbs of torque at the flywheel."

What thread did this come from?

quote Originally posted by Bloozberry: The manual transmission axle rods have 1.063" diameters... ...there are 32 splines and the spline max diameter is 1.024":

That's 26mm x 32 spline... on a 2.5mm module (Which is metric for "pitch")

[This message has been edited by Will (edited 03-13-2014).]

When I was researching my axles I found this site extremely helpful. http://www.empius.com/acatalog/acatalog.html

------------------
yellow 88 GT, not stock
white 88 notchie, 4 banger

quote Originally posted by seajai: When I built my axles, I found a lot of cars used the 1.063" dia axle with the 1.024" 32 spline count. I just wandered through the pick and pull with a digital calipers and measured axles until I found the length with the dia I needed.

Thanks for the input but I'm not sure how you determined how many teeth were on the axle rods without pulling off the boots... something that the yards around here certainly won't let me do. I've found that measuring the axle rod diameter isn't a sure-fire way to determine what diameter and number of teeth are hidden under the boot. Lots of axles are turned down to a smaller diameter at the ends.

quote Originally posted by Will: What thread did this come from?

www.fiero.nl/forum/Forum3/HTML/000030.html

quote Originally posted by Will: That's 26mm x 32 spline... on a 2.5mm module (Which is metric for "pitch")

Aha! That makes perfect sense. Thanks for that.

quote Originally posted by ccfiero: When I was researching my axles I found this site extremely helpful. http://www.empius.com/acatalog/acatalog.html

Thanks ccfiero... that was one of the many websites I checked out but either I'm blind, or they've changed the content of the website over the years since I could only find info on boots and spindle nut sizes no matter what topic from their front page that I downloaded. My biggest difficulty was finding specs on axle rods... still haven't found any.

I've had a few helpful people PM me with the parts they cobbled together, but again, without dimensions it's still a crap shoot. From my drawings, I estimate that I'll need an axle rod that is about 400 mm (15.75") long for the driver's side, and one that is about 490 mm (19.3") long for the passenger side. These are quite a bit longer than the typical Corsica, Beretta, Caddy axle rods that some have suggested, but I can't quantify the difference because axle rod lengths for those cars are the missing link. The exact lengths of my axle rods can't be determined either until I have the tripot joints and CV joints I plan to use since the depth of the tripot cup, the depth the tripot seats inside the transmission (or intermediate shaft), and the depth the CV joint seats in the knuckle bearing all affect axle rod length. Once I pick up my Cobalt SS axle assemblies today, I'll have everything I need to calculate how long my axle rods need to be. Then, if someone can suggest a source for an axle rod with the right splines and the right lengths, I could avoid having to cut and re-spline an old Fiero axle rod... but I'm not holding my breath!

There is http://www.raxles.com/hybrids.aspx that can make them for you

------------------
yellow 88 GT, not stock
white 88 notchie, 4 banger

Custom axles can always be made by Moser, Driveshaft Shop, Raxles, Strange, etc. if you provide specs... not cheap though.

Who does the spline work? I have a BMW application that will require some custom splines.

quote Originally posted by ccfiero350: When I was researching my axles I found this site extremely helpful. http://www.empius.com/acatalog/acatalog.html

quote Originally posted by Bloozberry: Thanks ccfiero... that was one of the many websites I checked out but either I'm blind, or they've changed the content of the website over the years since I could only find info on boots and spindle nut sizes no matter what topic from their front page that I downloaded.

They must have downsized and only focus on VW axles now, but they used to have some of the best catalogs. They had pictures with overall axle lengths plus the spline info on both ends. Another of their catalogs showed the part # for the Tripod and CV ends by application and they also had catalogs with dimensioned pictures of the ends by part number and these show the actual axle shaft spline. Here is the Fiero outer CV diagram for example:


My process to narrow down axles is not very "precise" and takes time, but it works... mock up a stock Fiero axle or G6 or Cobalt Axle and determine how much "too short" it is and add this length to the compressed lenght for the axle you used. This gives you the needed overall compressed length. Then look at overall axle lengths that are +/- 1" of that length. Then compare the geometry (length & spline count on the actual axle shaft ends) of the tripod housings and CV joints and back into one that "should" have the right length axle shaft with the right spline.

For example with the various EMPIUS catalogs, you can find all tripods with the 34 spline to fit in a Fiero transmission, then match that part number to the applications for each, then take the applications and find the part # and compressed length for the entire axle and sort them by length. Here is a list of all the GM axles with a matching tripod for a Fiero transmission by length. I haven't taken the time to go through the list and seperate out the ones with 32 splines on the axle shaft and the wheel ends are various styles (small 33, 27 and large 33), but it does show the available lenghts for stock axles with atleast 1 matching end (for a stock transmission, not the F40).

code:

---

Length		EMPIUS part #
27 ¼” 		80-1315
26 7/8”		80-1305
26 ¾”		80-1425
26 5/8”		80-1400
26 ½”		80-1319
25 ¾”		80-1309
25 5/8”		80-1833
25 5/8”		80-1237
25 7/16”	80-1307
25 1/8”		80-1341
25 1/16”	80-1339
24 13/16”	80-1805
24 11/16”	80-1325
24 ½”		80-1435
24 ½”		80-1317
23 ½”		80-1393
23 3/8”		80-1377
21 ¼”		80-1329

---

I never thought to include the axles from other OEM's outside of GM, but EMPIUS catalogs list most of the common makes/models. If you would like I can email you all the EMPIUS catalogs and you can spend literally days sorting through the info...

quote Originally posted by Bloozberry: My biggest difficulty was finding specs on axle rods... still haven't found any.

Archie has a list of GM axle shaft lengths, you might PM him for the length you are looking for.

[This message has been edited by fieroguru (edited 03-14-2014).]

Weird. Since Empi was a big VW parts supplier, I was surprised to see they had an axle cross reference for any other axles.
That's what I knew them from was VW parts.

Jay

quote Originally posted by Will: Who does the spline work? I have a BMW application that will require some custom splines.

I still have to get the details, but the owner of one of the local machine shops told me of another local shop that has the ability to cut new splines cold. I live in farm-country with lots of machinery repair shops nearby.

quote Originally posted by Fieroguru: [EMPIUS] used to have some of the best catalogs. They had pictures with overall axle lengths plus the spline info on both ends.

Thanks Paul for that list... I should be able to follow your procedure to find an EMPIUS part number from your list with the correct overall length, then, assuming the axle rod will also be close to the length I need, I can cross reference the EMPIUS part number to the equivalent Interparts number using the extensive listings at www.interparts.com. From that same site there are tables that list the cars that use each of their part numbers. Once I know which cars have which axles, I can then go shopping in the salvage yard. In the mean time, I'll find out a bit more about how much it costs to get an axle re-splined... it still might be easier and cheaper to do that.

As promised, here are the rest of the photos showing how to disassemble a Fiero axle assembly. Similar to the CV end of the axle, I had to cut the two retaining clamps off the tripot boot. However unlike the CV joint, the tripot housing simply slides right off the tri-lobe roller assembly inside:



This is what the tri-lobe assembly looks like after cleaning the grease off it. You have to be careful when cleaning it because the large rollers can easily slip off the ends of their shafts along with the needle bearings which are not retained by anything except the stickiness of the grease.



To get the tri-lobe assembly off the end of the axle rod, you have to remove two snap rings. The first one is a large heavy ring that has to be opened up with snap ring pliers and slid away along the axle:



Only then can you expose the small snap ring hiding under the tri-lobe assembly by sliding assembly further onto the axle rod. The small snap ring is easily removed with a pair of small standard screwdrivers:



With the small snap ring removed, the tri-lobe assembly just slides off the end of the axle rod. Here are the pieces:



Since I had the CV and tripot joints for both the automatic and manual Fiero transmissions handy, I thought I'd show them side by each to give an idea how different they are in size, even though I won't be using either. Perhaps this will help someone choose the right joints for a future project. The manual transmission tripot joint is the more robust one on the left while the joint for the automatic is on the right:



Here are the CV joints... again, the manual CV joint is on the left (yellow) and the automatic CV joint is on the right (green):

I picked up both Cobalt SS axle assemblies a couple days ago for $310 total, including taxes, which seemed like a pretty good deal. When I ordered them from NAPA, I initially asked for the price difference between new and remanufactured axles. In their crazy cost structure the remans were $209 each unless I brought in cores which would lessen the price by $59. New axles were $137 each with no need for a core return. I just don't get it. Needless to say I went with the new axles. Here's the part number:



Here's what they look like out of the box:



Interestingly enough they're manufactured by Interparts... the company whose website I posted earlier and where I found some useful specs.



The exterior of the Cobalt CV joint is shaped slightly differently than the Fiero's, but all of the key exterior dimensions check out the same:



Most importantly, the Fiero rear wheel bearing slides onto the Cobalt CV joint spindle like it was made for it. A perfect fit!



Although I haven't removed the Cobalt CV joint's spider assembly, cage, and balls, they too appear to have the same dimensions as the manual Fiero CV joint with the exception that the Cobalt's CV spider has 25 splines for the axle rod, whereas the manual Fiero's has 32 (Fiero automatics have 29). For example, the Cobalt's cage measures 2.250" across, just like the manual Fiero CV joints (this is the Fiero's):



I'll expand on the significance of this later on as I summarize all of the possible ways to modify the Cobalt parts to fit any Fiero with an F40 transmission. In the meantime, here is quick comparison between the Cobalt and Fiero tripot joints. Notice how the Fiero joint is lobed and the Cobalt's is cylindrical. Also note how much larger the splines are on the Cobalt's stub shaft. The Cobalt's tripot stub shaft has 27 splines compared to the Fiero's 34. Bear in mind that the Cobalt SS uses the F35 five speed transmission, but it has the same tripots as the G6 F40 six speed transmission.



Enough comparisons... the next thing I needed to do was figure out how much longer my new axle rods must be than the Cobalt's. Tearing a page from Fieroguru's methodology, I first separated the Cobalt tripot from the axle assembly and cleaned up the grease.



Next, I seated the empty Cobalt tripot cup into the F40 driver's side differential:



I used a rubber mallet to make sure it was completely seated... here's how deep it sits:



Next, I took the remains of the Cobalt axle and shoved the CV joint into the knuckle until it seated hard against the backside of the bearing:



Here's how much too short the Cobalt axle is:





Although it's pretty straight-forward, I'll be able to accurately calculate how much longer my new axle rods have to be by continuing with Fieroguru's approach in my next post. (Thanks Paul for the idea!)

[This message has been edited by Bloozberry (edited 03-18-2014).]

Blooze .... I am REALLY reading this carefully...... as you probably know I'm gathering parts and info to do my F40 to SBC swap.... your write ups are FABULOUS thanks for all the work and info you are sharing in this excellent thread ...KUDOS to you

Danyel

quote Originally posted by Bloozberry: In their crazy cost structure the remans were $209 each unless I brought in cores which would lessen the price by $59. New axles were $137 each with no need for a core return.

The new ones may be made out of the finest Chinese lead... be careful. Other people have had problems with new and reman aftemarket axles being much weaker than the stock ones.

quote Originally posted by Bloozberry: 25 splines for the axle rod,

What's the OD of that shaft?

quote Originally posted by Bloozberry: Also note how much larger the splines are on the Cobalt's stub shaft. The Cobalt's tripot stub shaft has 23 splines

What's the diameter of that shaft?

quote Originally posted by Bloozberry: Bear in mind that the Cobalt SS uses the F35 five speed transmission, but it has the same tripots as the G6 F40 six speed transmission.

The F40 and F35 both use 27 spline for the differential to tripod interface, but the design of the actual tripod housings are indeed different. The F40 one is kinda fiero shaped where it is a formed housing, but the real differnece is in the diameter of the rollers within the tripod housing - they are much larger on the F40 one. The F40 also uses 1 male and 1 female tripod. Here is a picture of the female one:


It looks like the F35 tripods are of a similar design as the Equinox and other GM 5 speed auto tripods.

Where the ability to interchange axles for an F40 hits a road block is normally on the tripod side. If the housing uses larger rollers (F40) and the roller housing has a unique spline count, then it becomes difficult to either find a tripod roller setup that fits the housing, or a longer (or shorter) axle shaft with the same splines for the roller housing. As far as I know, there is no other compatible roller housing for the G6 tripods so you have to find an axle that will slide into the G6 roller housing. The G6 axles switched splines on the actual axle shafts from 33 to 34 or 34 to 33 and the 33 is a no-go as far as finding other GM axles. The 34 was a possibility, but when my G6 axles showed up, they were both 33 so I never got a chance to play with a 34 spline version.

I am hoping that the tripod rollers on the Cobalt axles are the same as some other GM applications.

Thank you Blooze, Guru and all for this discussion. My combo is Gen 1 ZZ3 to F40., shifted so far toward the driver's side that the F40 interferes with both the chassis and cradle on the driver's side. That issue, resolved and set aside, I find it curious that the Cobalt axle has 24 splines. I have a Cobalt SS axle, a Saab 9-3 axle and a G6 (male end) axle. All have 27 splines and all fit my F40. What am I missing? Can both 24 and 27 splines engage in the same trannie?

Somewhat confused in Arizona,

Ken

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'88 Formula V6
'88 GT TPI V8

[This message has been edited by kennn (edited 03-18-2014).]

quote Originally posted by Danyel: I am REALLY reading this carefully

Thanks Danyel for following along. Hopefully a few of us can pool our information together and de-mystify what parts can be used. As I mentioned, I'll summarize my findings soon.

quote Originally posted by Will: The new ones may be made out of the finest Chinese lead...

Yeah... these were in fact made in China, but it's hard to know the origin of the part in advance. I guess I'll have to wait to see how well they hold up.

quote Originally posted by Will: Who does the spline work? I have a BMW application that will require some custom splines.

I got more information about this today. I doubt it would be worth your while to send your axles up North, but the local shop that can do the work is called Scotia Machine Service Ltd in Kentville, Nova Scotia (902) 678-1100 (about 15 mins from my place). He estimated it would cost between $60 - $70 per end.

quote Originally posted by Will: What's the OD of [the Cobalt axle rod] shaft?

The spline major diameter is 1.075", which is only 12 thousandths larger than the Fiero manual transmission axles. The machine shop believed the difference to be insignificant for the purposes of re-splining the Fiero shaft.

quote Originally posted by Will: What's the OD of [the Cobalt tripot stub] shaft?

I didn't check and the tripots are now rather tightly seated in my transmission. Those snap rings really hold on!

quote Originally posted by Fieroguru: The F40 and F35 both use 27 spline for the differential to tripod interface, but the design of the actual tripod housings are indeed different.

I stand corrected. I remember now why I wanted to use the Cobalt tripots instead of the larger G6 ones. I wanted to avoid any potential clearance issues between the engine block and the passenger side tripot. I recall this was a problem area in your LS4 thread... to the point that you needed to hammer down the boot clamp nib on your G6 tripot to be certain it wouldn't hit the block. The Northstar has a similar clearance issue when using a jack shaft. You sent me the exterior dimensions of the G6 tripot a while back and I remember thinking that the clearances would be too close for comfort so I went with the smaller (albeit weaker) Cobalt tripots.

quote Originally posted by Fieroguru: Where the ability to interchange axles for an F40 hits a road block is normally on the tripod side. If the housing uses larger rollers (F40) and the roller housing has a unique spline count, then it becomes difficult to either find a tripod roller setup that fits the housing, or a longer (or shorter) axle shaft with the same splines for the roller housing.

You hit the nail on the head. There are many different parts that can be cobbled together to make any number of (outer) CV joints and axle rods mate up with the Fiero bearing. The problem is mating one of those axle rods to a tripot spider from the g6 or Cobalt/Equinox. We should start a new thread called "F40 Axle Compatibility in a Fiero" where the different combinations and permutations of parts that will match up to make a single axle assembly are listed in tabular format. The written format is just too complex. Perhaps I'll start such a thread once I get a few more measurements from the Cobalt axles... but at the moment I'm having a hard time removing the Cobalt CV joints off the axle rods. They use a blind snap ring but the shoulders of ring groove were likely cut too sharp or too deep to pull them off. Grrrr...

quote Originally posted by Bloozberry: but at the moment I'm having a hard time removing the Cobalt CV joints off the axle rods. They use a blind snap ring but the shoulders of ring groove were likely cut too sharp or too deep to pull them off. Grrrr...

Remember our different approaches of removing the decklid hinge boxes? This is another time where crude/brute force can be the quicker/easier method. Take the boot off the shaft, so all that is left is the axle shaft and outer cv. Find a stout surface with a hole or slot large enough to pass the axle through, but not the CV housing. Get some gloves, pass the axle shaft through, grab it with your strong hand, then yank it down as quick and has hard as possible (and watch for flying CV housing). Repeat as necessary.

You could clamp the CV end in a vice (or pass the stub shaft through a hole in the wall) and then use some U-bolts around the shaft to attach a hook that could be used with a slide hammer.

[This message has been edited by fieroguru (edited 03-18-2014).]

Do you have a few moments to address what would be different in using a 'pre '88 as a source, as those bodies are far more common to potential builders?

If you haven't addressed this yet, how would this interact with a 'pre '88 front end, which some may want to use to avoid the pitfalls of harder to get '88 wheel bearings (or just because they started with a 'pre '88 body).

quote Originally posted by fieroguru: This is another time where crude/brute force can be the quicker/easier method.

I already tried that method and a slightly different one with the slide hammer. Then I took the axles to the transmission shop where they tried with a weird combination of bearing pullers and even they couldn't get them apart. I then took them to the machine shop that's going to do the re-splining and left instructions that it didn't matter if either the Cobalt axle groove, snap ring, or the spider broke since I'm not using any of those parts.

[This message has been edited by Bloozberry (edited 03-19-2014).]

quote Originally posted by Bloozberry: Max, would you mind if we took this up in your "redesign" thread? I'd like to try to keep my thread on topic since axles are confusing enough!

Yes, of course, much better idea.

To get back on track, here's how I figured out how much longer my axles rods needed to be:

I started with the Driver's side so first, I picked a convenient reference point on the outer CV joint. I chose the nice line formed where the tapered portion meets the flat portion. Next, I chose another convenient point on the back side of the knuckle; the large flat area next to the bearing hole. Then I made sure the CV joint was fully seated in the knuckle and measured the distance between the two points: 25 mm (red arrow)



Next, I pulled the CV joint out of the bearing and slid the axle assembly towards the transmission until the tripot spider assembly bottomed out into the tripot cup. Then I measured the distance between my two reference points once again. This time I got 107 mm:



Finally, I took the same measurement after pulling the axle back towards the wheel until the tripot rollers were close to the edge of the tripot cup and almost ready to fall out. I got 65 mm this time. Here's a summary of the measurements:



To find out how much longer my new driver's side axle needs to be compared to the Cobalt SS axle, I went through the following simple calculation:

((107 mm - 25 mm) + (65 mm - 25 mm)) / 2 = Additional Length

(82 + 40) / 2 = 61 mm Additional Length

I repeated the same exercise for the passenger side and found that the passenger axle needed to be 140 mm longer than the Cobalt SS axle. I didn't photograph me holding the ruler since I figured it would be overkill, but for interest's sake, here's how deep the tripot joint seats into the jack shaft. You can see why I was a bit concerned that the larger G6 tripots might not have enough clearance to the side of the engine block:



So, the only piece of the puzzle that is missing is the length of the Cobalt axle rods, so that I can add 60 mm to one and 140 mm to the other. Unfortunately I couldn't measure the Cobalt axle rods since I couldn't get the CV joints off them. I know it's a bad idea to give the machine shop too many instructions, but I dropped off the Cobalt axles and the Fiero axles with instructions to remove the CV joints, measure the Cobalt axle lengths, add 60 and 140 mm to that length, then cut and re-spline the correct ends of the Fiero axles to those new lengths. I made sure to give the shop diagrams, simple step-by-step instructions, and my phone number so that I could watch (and take pictures) when they modify them. They're back logged with work right now so it will be about two weeks before they're done.