did you have any dogbones on the top? If not I would thing that the torque from the engine caused the damage since your torque line being the engines center line, being higher than the mounts allowed the engine to rock this caused all the stress to be below the tranny so most of the force was placed on the tranny it's self. I would say you need dogbones up top to take this force off of the lower mounts and the tranny. Let the lower mounts hold the bottom in and dogbones to hold the top.

Example would be taking a yard stick and securing the bottom. Now push on it mid way up. Where's it break? At the bottom. Now secure the top and bottom. Push at the mid point, what happens? It bends depending on how much you pushed it may break in the center. But all in all your tranny was the weakest point between the front and rear mounts and the engine.

This is my thaughts. If you have upper dogbone mounts then I have no clue unless it twisted then you may need another mount up top to stop that.

(EDIT) Just noticed the dog bone mount but the lack of any mounts in the rear right corner of the set up. It looks like the same thing as experienced on a threewheeler. The rear right corner of your motor Moved DOWN. The dog bone did nothing but swivle down and limit the movement to the length of the bone. If your rear dogbone mount was LOWER on the car or higher on the engine this couldn't have happened.

[This message has been edited by stuartlowery (edited 04-20-2004).]

quote Originally posted by SplineZ: Wouldnt solidly mounting things cause the metal to fracture and then pull apart? I'd think you'd want some play to cush any shock... James Z

OK, visualize it this way. Stand with your head 2" away from a concrete wall, and slam your head into the wall as hard as you can. That's what happens when there's room to "give". Next, "solid mount"...press your forehead against the wall...now, without moving your forehead from the wall, slam your forehead into the wall as hard as you can.

Which one does more damage?

Note: I *did* say VISUALIZE. If you actually try this, PLEASE don't blame me....

The meat of it is, solid mounting will spread any torque/forces along the entire chassis (cradle, whatever). It WILL find weak links for you, if there's a spot that flexes. "Soft" mounting gives it the "slide hammer" effect, and the instantaneous shock when the "give" runs out WILL tear stuff up.

Jeremy B.

Solid mounts I would say put your forehead against the wall and hit the back with your fist. Poly put a thin cushin between your forehead and repeat above. Rubber put a weaker thicker cushin there and do again. The poly is the best but if your engine is allowed to twist from improper geometry of the dogbone you'll still have failures.

And here's another option for an engine strut.

Good luck on the fix Amir.

quote Originally posted by stuartlowery: Solid mounts I would say put your forehead against the wall and hit the back with your fist. Poly put a thin cushin between your forehead and repeat above. Rubber put a weaker thicker cushin there and do again. The poly is the best but if your engine is allowed to twist from improper geometry of the dogbone you'll still have failures.

Only if something external to the motor is beating on your motor. The drivetrain is it's own "force". Nothing is "hitting" it. If it's not allowed to move, there's no impact. No impact, no concentrated blow.

Like I said, solid mounting will find weak links. Basically anything that is allowed to flex will break. Fix any point that flexes, breaks, or is weak, and one of two things will happen...all the force goes into your tires, and they spin, or all the force goes into the frame, and you do wheelies (traction willing). In reality, you don't want any energy going into ANYTHING but turning the wheels. Any movement in the motor, cradle, etc. is just wasted power.

Or, the third option...you find the weak links in your drivetrain. Wheel, axle, hub, diff, tranny, clutch, crank...whatever.

Jer

OK I didn't read the whole thread so forgive me if this has already been posted, but from that pic of the twisted tranny mount it looks like it's the bracket got tweaked not the mount itself. I shredded that bracket with a stock motor before I got poly mounts. It just came apart and the whole engine trans assembly shifted of centerline by a good inch and a half. Put hella stress on the dogbone and axles.

When I replaced the mount with wcf poly, I also got the laser cut 1/8" steel brackets from rodney. Way stronger than that stampted steel crap and over a year later it is all still rock solid.

[This message has been edited by 88GTNeverfinished (edited 04-20-2004).]

quote Originally posted by Rare87GT: Tom it was rebuilt 17,000, but to what extent I have no idea. I am assuming just the normal stuff that would be replaced in a transmission (flywheel, clutch, t/o bearing). I really doubt that the tranny was gone through so I have no idea. The tranny had 120,000 miles on it when I bought the car so I would assume that the differential bearings and everything else inside had the same amount of miles on it. When we put the Spec Stage III in it and new flywheel and t/o bearing nothing else was replaced at this point. This would add to the reason it failed, but I still think the mounts had a big deal to do with it. I plan on adding another mount on the engine side.

I've seen the insides of a couple Getrags with 120,000 miles on them, not very much wear at all on the parts, except for synchro rings, the bearings you usually replace just because you have it apart, and to be extra safe. Don't be surprised if you have failed parts inside, that would be expected with that much case damage. You should strongly consider solid mounting of both engine and trans to the cradle. I does not transmit that much vibration to the chassis, personally, my car has never had a failure, or cracks since 1993, and I'm not running an upper torque bar, or dogbone. Just take the time to research the best way to position the mounts (line for line with trans and engine), and have a good welder fabricate to the cradle. Even if by remote chance you had an internal failure, this setup is better in the long run, with no worry about worn bushings.

I understand completely Tom what you mean about it all. I think there is a weak point. I know the tranny could handle it, its just the fact that something else was used as the culprit and allowed it to make the tranny even weaker than it should have been. I haven't seen that many grenaded Getrag's out there, so I know its one of those things that makes everyone wonder. My engine does have an upper dog bone as well just to let everyone know. We did tear down the Getrag tonight. The spider gears grendaded. Chunks of it is all inside the case. No damage to the clutch, flywheel so forth. But the crack even allowed for the VSS sensor up top to have a crack right beside it as well. So is it the poly mounts or the cradle at fault, anyone have a clue. I know several people running these exact same poly mounts with their 5spd. Low_Key, me, I know a few others, I think revin if I am not mistaken, why mine!

-Amir

pics in the next post by me.

Hey Amir, that looks an aweful lot like a broken spider gear laying in your bellhousing. You know what the problem is now! You need to invest in a LSD. The broken transmission had little to do with mounting but alot to do with unequal tire spin. But the bad mounts is probably what caused the shock load to get them to break like that. What you have had happen is NOT uncommon at all. Ive seen it first hand more then 10 times. Once in one of my cars. Switching to an automatic will not help much, but putting in an LSD unit will solve the problem. If you broke the case from sheer power, your differential would have not shattered like that. A later model Getrag will be a better choice too since it's differential pin is hardend steel AFAIK. It will last longer but a really hairy burnout could still destroy that too.
Heres some good reading material on what you have had happen
http://www.thrashercharged.com/tech_htm/differential.shtm
Best of luck on the next one.
Oh heres a pic of the same thing in an automatic the spiders got through the case here too!

[This message has been edited by Fierobsessed (edited 04-21-2004).]

Hmm....After seening your new pics, it looks more like the spider gears in your diff exploded. That is typicly caused by excessive wear or play in the diff. I doubt it was a mouting failure.

------------------
Don Hites
88 GT, Getrag 5spd, 4.9 v8 with a Delta cam and other heavy mods.
88 Coupe 5spd Duke
(now under restoration)

quote Originally posted by Rare87GT:

Unrelated, and don't think it could possibly be related to the failure in any way...but it looks to me like that disc was installed backwards. The scraped area around the center looks like it's from contacting the flywheel bolts...and that's the side that should be towards the pressure plate.

And while I'm straying off-topic here...did the spec clutch shudder at all, or did it just engage sharp?

Still love the car, and think you should go back with whichever tranny you want...just minimize movement on either one. Personally, I think there was an issue with this tranny, and I wouldn't be afraid to put another Getrag back in it if it were mine, if that's what I wanted in it. Play in the carrier bearings, wear on the pins the spider gears ride on, etc. You really shouldn't have had enough traction OR torque to do that to a healthy Getrag, in my opinion.

Take care---
Jeremy B.

Amir,
Stop scaring me about the mounts ! i have 5 points of contact.
Just keep saying that is IS the tranny fault not the mounts! please.
Then again...so far so good

maybe that engine is way too much for you....I guess I will take it from ya for free! we'll find ya a nice 4 cyl. that you can trash around with!!! lol

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

98 3800SC GTP motor,3.4 pulley, Getrag 5sp.
custom hood, trunk, side scoops, IRM front spoiler, 17" excel's , dk.Shadow Grey

quote Originally posted by HitesFiero: Hmm....After seening your new pics, it looks more like the spider gears in your diff exploded. That is typicly caused by excessive wear or play in the diff. I doubt it was a mouting failure.

How can you tell if the spider gears broke before or after the case cracked????

why do people think solid mounting will be better for the trans.. it only applies more force since there is nothing to cusion like rubber or poly (unless you are adding more mounts like tie rods to other locations on the transmisson and frame)

but seriously proper captive rubber mounts will put the least stress on the engine and transmission.. stock fiero mounts are not enough but you can also use rubber bushings in place of the poly in those aftermarket trans mounts.. and if you still aren't sure then reinforce the trans case itself.. but give it some room to move the force and vibration from solid mounting is just the thing to case stress and fatigue cracks in cast aluminum

in this case i think the casing went second

quote How can you tell if the spider gears broke before or after the case cracked????

I see the point your tring to make Cali, I just gave an oppinion based on my personal experiences. I wasn't tring to definitvly state that the spiders where the piont of failure.

------------------
Don Hites
88 GT, Getrag 5spd, 4.9 v8 with a Delta cam and other heavy mods.
88 Coupe 5spd Duke
(now under restoration)

quote Originally posted by Fierotech: Unrelated, and don't think it could possibly be related to the failure in any way...but it looks to me like that disc was installed backwards. The scraped area around the center looks like it's from contacting the flywheel bolts...and that's the side that should be towards the pressure plate. And while I'm straying off-topic here...did the spec clutch shudder at all, or did it just engage sharp? Still love the car, and think you should go back with whichever tranny you want...just minimize movement on either one. Personally, I think there was an issue with this tranny, and I wouldn't be afraid to put another Getrag back in it if it were mine, if that's what I wanted in it. Play in the carrier bearings, wear on the pins the spider gears ride on, etc. You really shouldn't have had enough traction OR torque to do that to a healthy Getrag, in my opinion. Take care--- Jeremy B.

It shuddered a little bit yes. But that was due to the fact that I had poly mounts and a suspension that doesn't give much. The disc being installed backwards has nothing to do with this and will not affect the life of the clutch at all.

quote Originally posted by Rare87GT: It shuddered a little bit yes. But that was due to the fact that I had poly mounts and a suspension that doesn't give much. The disc being installed backwards has nothing to do with this and will not affect the life of the clutch at all.

I was asking about the shuddering, simply because I have a Spec stageII, that shudders like MAD. Went with the 2 instead of the 3 because it wasn't supposed to shudder. Think I just have a bad one, and it's coming out in a couple of weeks.

Definitely, the disc being installed backwards has nothing AT ALL to do with the failure, and nor would any shuddering; I was asking for other reasons. But I would disagree about the life of the clutch...the fact that the flywheel bolts are grinding into the disc sorta tells you something isn't right. It's not a big deal...just pointed it out so the same mistake wasn't made again. If you WANT it installed backwards for some reason, by all means, whatever makes ya happy!

Jeremy

quote Originally posted by Fierotech: I was asking about the shuddering, simply because I have a Spec stageII, that shudders like MAD. Went with the 2 instead of the 3 because it wasn't supposed to shudder. Think I just have a bad one, and it's coming out in a couple of weeks. Definitely, the disc being installed backwards has nothing AT ALL to do with the failure, and nor would any shuddering; I was asking for other reasons. But I would disagree about the life of the clutch...the fact that the flywheel bolts are grinding into the disc sorta tells you something isn't right. It's not a big deal...just pointed it out so the same mistake wasn't made again. If you WANT it installed backwards for some reason, by all means, whatever makes ya happy! Jeremy

Yeah I understand. It can affect the life but nothing at all like this will seriously do anything as far as down the road. It may make it not the longest lasting clutch but then again this is a high performance clutch that isn't suppose to last 100,000 miles so either way I think it will be fine. See ya later.

quote Originally posted by California Kid: How can you tell if the spider gears broke before or after the case cracked????

The case would have never cracked if the spider gears were not forced through the case. A case can crack that way from sheer power, but it would have to be a very poorly cast case with an exceptionally strong engine behind it, and a failure of that sort 99% of the time will NOT destroy the spider gears, they are solid steel parts safely incased within a very strong cast iron/steel differential. It's when they get out of that part of the differential that the differential itself mashes the spiders through the case. This can happen two ways, or a combination of the two (witch this particular transmission suffered from) The differential pin is in most cases just regular steel, and with the two spider gears wanting to shear it off, while they rotate on the shaft at great force, it's likley that they will start to eat away at the pin and the spider gears wear down with it, eventually either the spider gears or the differential pin gets too thin and just breaks, causing all the parts to get mashed out through the case. The mounts are a completly seperate problem, as so is the strange wear or rubbing marks on the clutch plate. At least it is VERY easy to check the condition of a differential. Just jack up the car, put it in gear (manua) or park (automatic). make it so one wheel can't turn. go to the other wheel and rotate it back and forth alittle, it will stop a few degrees in either direction. I had a transmission where I would get 60º of rotation before it stoped. The differential pin was eaten 1/3'rd the way through. The metal got into the fluid and jammed up the valve body, delayed and no shifting conditions. And this was caused by doing donuts in a 4 cyl automatic. Basically my argument has since then been, burnouts, donuts and open differentials are a really destructive mix. LSD is the only way to go

quote Originally posted by Fierobsessed: The case would have never cracked if the spider gears were not forced through the case.

My exact point back on page one. The case exploded outwards as was evidenced by picture number 2 !

Amir, good luck with your repairs, I just hope it didnt damage the bottom end of your engine......................

quote Originally posted by FieroHarry: My exact point back on page one. The case exploded outwards as was evidenced by picture number 2 ! Amir, good luck with your repairs, I just hope it didnt damage the bottom end of your engine......................

Nothing happened with the bottom end of my engine. It is perfectly fine. The tranny is toast, that's all that happened. What do you mean by damage the bottom end of my engine? By what factor do you mean, like when the casing ripped apart metal objects hitting it or what do you mean?

I think some JB Weld would fix that

Russ

damn the decisions!!!!! soild mount? poly? half half? getrag? 4t60? 4t65? E? HD? new axles? used? arghhh LOL

Killer info going on here though.. Keep it up!! She'll be back on the road in full glory all in due time Amir!!!

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

Ferrari 308 GTB rebody on a modified 86SE chasis Soon to have a highly hooped up 3800SC..Ohh yeah baby!!
Contacts _ AIM / Zildjianfx _ Yahoo / djdraggin
Remember, always brush your milk, drink your teeth, dont do sleep and get eight hours of drugs.

quote Originally posted by Rare87GT: Nothing happened with the bottom end of my engine. It is perfectly fine. The tranny is toast, that's all that happened. What do you mean by damage the bottom end of my engine? By what factor do you mean, like when the casing ripped apart metal objects hitting it or what do you mean?

You never really did mention whether or not the tranny caused the tires to lock up while rolling down the street!
If in fact you locked up the tires/drivetrain hard enough (rotational forces coming to a complete halt) to damage the "cradle" imagine what you might have done to the relativley soft metal in the crank/rod bearings.
I have seen drive train's lock up and actually twist and even break crankshafts in half.
Its your time and money, ask around and decide for yourself. If it was mine, I would at least remove the pan and roll out 1 each crank/rod just to inspect.
But hey, Im anal about things like that because I cant stand to "re-due" things like removing engines and trans because of something easily overlooked.

Harry,

you have to think about what the weak link is though. Is a spider gear going to lock up causing the crank to break, or is the gear going to break. Well I think a spider gear that at the thinnest point and most prone to cracking is about 3/16-1/4" thick. A crank journal is 2" thick. Before major engine damage would happen, the flywheel bolts would break off. Thats happened to many 3800's. Nothing is wrong with the engine, the trannys life was limited. Tons of guys on club gp have shelled diffs, blowing pieces of transmission all over the track, with no engine damage whatsoever. Thanks

Ryan

all i can say is i hope to god that dosnt happen to me!

looks like ill be solidly mounting anything I do now... maybe even replacing my current mounts with solid ones..

Does anyone sell the peices or do I have to fab them?

James Z

I added this mount as well.

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98 3800SC GTP motor,3.4 pulley, Getrag 5sp.
custom hood, trunk, side scoops, IRM front spoiler, 17" excel's , dk.Shadow Grey

quote Originally posted by revin: I added this mount as well.

Do you have a wide angle shot? Where is the mount located in relation to the block and the cradle?

-bumppity-

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DON'T FORGET TO VOTE FOR THE FIERO!

Black '87 GT Auto - Daily Driver & Autocrosser
Eibach springs, Koni shocks, Kosei K1s, Kumho Ecsta V700s, poly bushings, rear swaybar, MSD ignition, shift-kit, custom intake scoop

rare87gt could you repost the pictures at the beginning of this thread, I really would like to see but now it only showes white squares with red crosses.

Thanx