It has been 50 degrees the past 2 days and most of the salt was washed away with rain last week, so it was a great opportunity to get the LS4/F40 Fiero out and put about 50 miles on it running around time.

I really like driving this car! Just a few months months and it will take over the daily driving duties from my truck.

And more updates,...YESSS
I have a blast in mine too, I know the feeling. I just have more "good days" for driving than you do

quote Originally posted by fieroguru: Most dynos are ran in whatever gear gets it closest to 1:1 ratio. So your LS4/4T65 should have been dyno'd in 3rd gear. I dyno'd my LS4/F40 in 4th gear (151 mph @ 7000 rpm).

That's a holdover from longitudinal RWD domestic cars, as 4th gear isn't just 1:1, it's "direct", in that the power flow is straight from the input shaft to the output shaft with essentially no friction from gear meshes. In a transmission without a "direct" gear, the gear that results in the highest number would be the one that strikes the best balance between the parasitic loss of accelerating the flywheel and the parasitic loss of accelerating the wheels & tires. In fact, a transmission WITH a direct gear may not necessarily make the highest numbers in direct.

quote Originally posted by fieroguru: If you wanted to make 3rd - 5th less long, you can swap in the short gear ratios for each and end up with this combo: code: Tire Dia RPM 1st 2nd 3rd 4th 5th 6th 24.9 6000 38 70 105 137 170 232

That's what I'm going to do, in addition to a custom 1-2 set.
Have you come across a part list for the F40? I'd like to find the part numbers for the 0.62 sixth gear pair. I'd be annoyed to have to buy an entire transmission to snag the second set of that ratio that I'm going to need.

quote Originally posted by Will: That's what I'm going to do, in addition to a custom 1-2 set. Have you come across a part list for the F40? I'd like to find the part numbers for the 0.62 sixth gear pair. I'd be annoyed to have to buy an entire transmission to snag the second set of that ratio that I'm going to need.

Yes, more transmission mods

I want to build a custom box for the Northstar car, but I have the MU9 unit with 3.55 gears from an '06 Saab 9-3 with high feature V6. An LLT, LFX or LGX will bolt right up to it. However, being an MU9, it has the 0.71 sixth... which is not nearly as good at what it should be doing as the 0.62 sixth. It would be super sweeeeeet if I could find the part numbers and buy those gears to swap them into that box... without having to buy an entire MT2 box to get the gear pair.

BUT... if they're more expensive than buying a transmission, I'll have to think about that.

I guess I need to find the nearest Saab dealer for a field trip.

quote Originally posted by Will: I guess I need to find the nearest Saab dealer for a field trip.

Do such places still exist?
Maybe a Fiat dealer?

There are no dealers of new Saab automobiles anywhere on the planet. GM closed Saab for good.

The parts numbers are iffy on most of the documents. For example a MYJ with the 3.55 I know the 6th gear part # on the input shaft, but the same document didn't show the corresponding part number for the 6th gear on the lower main shaft. It also shows the ring gear part #, but not the part numbers for either main shaft.

Can you post the number you have? I can at least google it.

The GM catalogs I've found online call out the clusters but not the individual gears:



And that one doesn't list prices for the cluster call outs.

ETA: Some old topics:

https://www.fiero.nl/forum/A...100421-2-095470.html
https://www.fiero.nl/forum/A...041015-1-042482.html
https://www.fiero.nl/forum/A...040710-1-036870.html

I visited a Saab dealership back in the day and looked at diagrams but did not get a parts list at the time.

[This message has been edited by Will (edited 02-08-2018).]

AC Delco 12787428 for the input shaft 6th gear, but I am not certain this is for the 0.62 ratio. CariD does list the specs for this gear, so with some work the ratio could be confirmed.

Nemiga.com used to list a couple of F40 component diagrams for the Opel and Vuxhall with the part call out descriptions as well as some part numbers, but now it looks like their catalog section isn't working (good thing I copied the info to excel and saved it).

[This message has been edited by fieroguru (edited 02-08-2018).]

I suggest you give these guys a shout and see if they can help:
https://www.onestopgearboxshop.com/
A UK based transmission parts house.

Or this company:
http://www.autocraftds.com/...we-do/transmissions/
A UK based transmission rebuilder.

[This message has been edited by FieroWannaBe (edited 02-09-2018).]

quote Originally posted by fieroguru: AC Delco 12787428 for the input shaft 6th gear, but I am not certain this is for the 0.62 ratio. CariD does list the specs for this gear, so with some work the ratio could be confirmed. Nemiga.com used to list a couple of F40 component diagrams for the Opel and Vuxhall with the part call out descriptions as well as some part numbers, but now it looks like their catalog section isn't working (good thing I copied the info to excel and saved it).

Awesome! Thanks!
RockAuto lists that part number for the G6 and Buick apps; 2006 G6 only
Summit also shows it, and lists it for Buicks with the MR6 transmission.
Based on those two facts, I think it's a solid bet this is for the 0.62 sixth.
Now... how to find the PN for the mating gear?
My former roommate is now a dealership parts guy, and he couldn't come up with anything, even giving him that number.

From this information below from CariD and the 0.62 ratio, the other gear should be 38 tooth. I looked at all listings on CariD for GM manual transmission gears and didn't find any 6th gears with a 38 tooth count.

ACDelco 12787428
Specifications:
Material: Steel
Inside Diameter: 1.39"
Grade Type: Regular
Outside Diameter: 4.191"
Tooth Quantity: 61
Inner Spline Quantity: 34

Really enjoying the build thread guru.

If I can help anyone with gearbox bits or part numbers I could try a Vauxhall dealer over here.

quote Originally posted by PK: Really enjoying the build thread guru. If I can help anyone with gearbox bits or part numbers I could try a Vauxhall dealer over here.

Thanks!

It would be really helpful if you could reach out to the Vauxhall dealer and do some part # searching!
Transmission # 55561696, 95518589, 55582837, 55593607, 55577502. This should be for a 2009 Vauxhall Insignia with the A20DTH diesel engine and the 3.091 final drive. If there are other transmission part numbers, those would be helpful to know as well.

Part #s for:
3.091 final drive ring gear
3.091 final drive upper main shaft
3.091 final drive lower main shaft
0.62 6th gear on the input shaft (should be 12787428)
0.62 6th gear on the lower main shaft

Thanks!

Hmm...give me a couple of days. I work with a Saab master tech (yes they still exist!) in my Air guard unit. He might be able to find something.

Thanks! Any information would be helpful.

Sorry, lol...It's funny, I see him about everyday, and now that I need him I haven't seen hide, nor hair of him. Still on my mind though!

I tried Vauxhall.

Unlike all other models, the insignia does not have the gearbox parts broken down into individual components. Not helpful. Since none of the components you listed could be located directly, I then tried entering the part number for the 6th gear on input shaft (12787428) and that part number did not exist on the system either!

Thanks for taking the time to look. They always said that the F40 was non-serviceable and it looks like that is indeed the case.

quote Originally posted by fieroguru: Thanks for taking the time to look. They always said that the F40 was non-serviceable and it looks like that is indeed the case.

Makes me wonder if it was made to be non-serviceable or if they just decided for some reason to abandon it?

GM has been using the F40 for well over a decade and it is still being used in current model year applications.

It is currently being used on turbo 4cyl and high feature V6s... GM didn't abandon it, they probably didn't expect or want people to swap ratios

As I continue to research the AWD upgrade, I found a diagram of the F40 AWD unit. It is a low exit (which is needed to get under the crankshaft) but the output points to the rear and it needs to point to the front. With a custom case half that bolts to the transmission, the output shaft should be able to be rotated about the ring gear 180 degrees which will point it in the right direction while keeping it a low exit.

Just have to get one of these units, take some detailed measurements for the housing, bearings, and bolt locations, buy a large chunk of aluminum, and spend lots of hours making chips...

Your level of ambition is inspiring. I think I take on some projects, but this is a whole 'nother level.

quote Originally posted by fieroguru: As I continue to research the AWD upgrade, I found a diagram of the F40 AWD unit. It is a low exit (which is needed to get under the crankshaft) but the output points to the rear and it needs to point to the front. With a custom case half that bolts to the transmission, the output shaft should be able to be rotated about the ring gear 180 degrees which will point it in the right direction while keeping it a low exit. Just have to get one of these units, take some detailed measurements for the housing, bearings, and bolt locations, buy a large chunk of aluminum, and spend lots of hours making chips...

Don't forget to get the other differential. The gear ratios will need to be be evaluated as well.

quote Originally posted by Bob2112: Your level of ambition is inspiring. I think I take on some projects, but this is a whole 'nother level.

Thanks! For me the fun is in the challenge, problem solving, and doing something unique!

quote Originally posted by Rickady88GT: Don't forget to get the other differential. The gear ratios will need to be be evaluated as well.

I plan to pick up the whole drivetrain if possible: transmission (so I get the differential with the spline extension to drive the AWD unit), the AWD unit, drive shafts, rear diff and axle shafts.

quote Originally posted by Rickady88GT: What vehicles were these available in?

AWD Saab 9-3 and 9-5 roughtly 2005 and newer for cars in the US. Many that I am seeing are 2009 and 2010. Several other applications over in Europe with Opel and Vauxhall.

[This message has been edited by fieroguru (edited 03-05-2018).]

It looks like the AWD unit was only offered on the 4cyl?
And that the AWD unit is driven by one side of the differential, the output for the passenger side wheel? If this is true, those spider gears are reasonable for driving 3 of the 4 wheels?
I am not familiar with this system, so how does the front differential work, left to right with the unit attached?

[This message has been edited by Rickady88GT (edited 03-05-2018).]

Across all models, the AWD was used with the high feature V6 as well as Turbo 4s (gas and diesel). The transaxle differential carrier has a hollow stub shaft that protrudes from the transmission case with splines that drives the AWD unit. The passenger axle passes through this stub shaft, but there is no mechanical connection between the axle and this stub shaft - they are free to spin independently of each other. This is the same method for a transverse AWD setup that Ford, GM, Chrysler and several imports use. Cases and gearset designed within the AWD unit vary, but the use of the hollow spline stub shaft off the differential carrier to drive the AWD unit is very common.

The nice part about doing it this way is the final drive of the transaxle differential is then applied to both front and rear wheels. The gear ratio of the AWD unit just matches the remote mounted differential (the rear one in the stock layout, it will be the front one in the Fiero). So you can change the final drive in the transaxle w/o needing to mess with the gear sets in the AWD or remote differential.

This direct coupling between the transaxle differential carrier and the AWD unit means there will be zero slip between the two, which I think is a good thing. I plan to run shorter tires in the front and install a high torque 1 way clutch that will allow the front wheels to rotate faster than the rears. Looking for a 2-5% slip so the rears will be the primary tractive force until they slip about 1" and then the 1 way clutch will lock and the fronts will get power to limit the rear wheel slippage.

Several of these remote differentials are also electronically controlled, so with the flip of a switch I can break the connection making the car 2wd again. This would be helpful with backing up as with the shorter front wheels and the 1 way clutch setup, I will drag the front tires some when reversing, so this electrical lockout would help with that.

[This message has been edited by fieroguru (edited 03-06-2018).]

Ok, this makes sense. The diagram just does not have the passenger side detail. So, how much torque is this AWD unit and drive shaft capable of handling? What diameter is the inner passenger shaft?

The 2009 Vauxhall Insignia VXR 4x4 has 320 hp and 321 lb-ft.

Power flows from the main output shaft to the differential ring gear, that is bolted to the differential carrier, which houses the spider gears. The spider gears are splined to accept the axles from both sides, but the spider gears are free to bias speed from side to side while the differential rotates at a constant speed. With the rear wheels off the ground, and the car idling at say 10 mph. Stop the driver side wheels and it has 0 speed, the differential is still spinning at 10 mph, and the passenger wheel is spinning at 20 mph. This is the way the stock Fiero transaxle (and every open differential) works.

The difference with the AWD unit is that the differential carrier has a hollow splined shaft that engages the AWD unit and puts power to the remote differential. The passenger side axle passed through the hollow splined shaft to engage the spider gears. The passenger side axle is free to be anywhere from 0 rotation to 200% differential rotation speed, just like the scenario above, while the AWD unit has to match rotational speed with the differnetial carrier it is directly coupled to.

Here is a picture of the Buick AWD unit that is very similar to the Saab one. You can see the smaller/longer splined shaft is the passenger axle and will engage the spider gear. It is poking through a shorter/larger splined shaft that couples the AWD unit to the transaxle differential carrier.

[This message has been edited by fieroguru (edited 03-06-2018).]

Ok, got it thanks.
The AWD unit can not bolt to a 2WD trans. The differential and bearings are specific to the AWD, and I would imagine that the trans case is as well?

quote Originally posted by Rickady88GT: Ok, got it thanks. The AWD unit can not bolt to a 2WD trans. The differential and bearings are specific to the AWD, and I would imagine that the trans case is as well?

Yes and no.

The differential carrier for sure is different between the 2WD and AWD versions due to the extra splined shaft.
There are 2WD cases that have the proper differential case bolt pattern for the AWD unit to bolt directly to (you just have to removed the axle seal), but the G6 F40 case is not one of them. A couple pages back I show the difference in the differential housing bolt patterns between the G6 case and the 3.09 case from Europe. The 3.09 case would allow the AWD unit to bolt to it.

So for my application, I will need the differential carrier from an AWD F40, then I was planning to make a new case that bolts to the transaxle (so I can flip the output shaft to the remote differential 180 degrees so it will go under the oil pan) and accepts the stock AWD extension housing to for the passenger axle. While I make this part, I will correct the differential housing bolt pattern at the same time.

quote Originally posted by fieroguru: Yes and no. The differential carrier for sure is different between the 2WD and AWD versions due to the extra splined shaft. There are 2WD cases that have the proper differential case bolt pattern for the AWD unit to bolt directly to (you just have to removed the axle seal), but the G6 F40 case is not one of them. A couple pages back I show the difference in the differential housing bolt patterns between the G6 case and the 3.09 case from Europe. The 3.09 case would allow the AWD unit to bolt to it. So for my application, I will need the differential carrier from an AWD F40, then I was planning to make a new case that bolts to the transaxle (so I can flip the output shaft to the remote differential 180 degrees so it will go under the oil pan) and accepts the stock AWD extension housing to for the passenger axle. While I make this part, I will correct the differential housing bolt pattern at the same time.

You will also need to flip the front differential. But from what I see, they are low pinion, flipping it would make it a hi pinion. Not that big a deal, if the gear oil still gets where it needs to go and not leak out.

quote Originally posted by Rickady88GT: You will also need to flip the front differential.

Correct.

My Saab Mechanic can't find any individual ratio P/N's...Sorry