I still think that if the case is seperating between the axles, the best bet is a steel girdle (I called it a cradle in my previous post, which is not correct). 1/4" steel plate bolted to both sides, tied together with more 1/4" plate top & bottom welded & bolted up (so it would be removeable). It would make it *very* difficult to split/blow the case apart.
~ Paul
aka "Tha Driver"

I *thought* I was wrong once, but I was mistaken.

Same old story maybe. Take a older well used Getrag and put a big V-8 on it and it blows. If there is any loosness on the differential bearings this is probably the end result. Had this been a fresh Getrag or a just rebuilt Getrag with new differential bearings correctly shimmed then it would be apples to apples. Installing the add on bearings would also help reduce this problem. Although with high HP, too big of slicks and a very stong clutch this may happen anyway.

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Rodney Dickman

Fiero Parts And Acc's Web Page:
www.rodneydickman.com
Rodney Dickman's Fiero accessories
7604 Treeview Drive
Caledonia, WI 53108
Phone/Fax (262) 835-9575

well the guy i was speaking of is definitely capable of toasting a 6 speed with a blink of an eye,or a slip of the clutch pedal..the first one is going in his 406 car that is on NOS..and that car hauls ass...but first a full out tear down and look-see will be in order...if there are any weaknesses i am confident he will expose them and rectify it too...tim..

quote Originally posted by flames4me: how much stronger are those 6-speeds, after i blew it at the strip another v8 fiero owner said NOT to get the 6-speed because there a generally weak tranny... there good for highway daily driving but not racing. thats what he said.

No one knows ANYTHING about the capabilities of the new GM 6 speed other than its 300 ftlbs torque rating.
WCF installs NSX transmissions into Fieros. The NSX 6 speed is weaker than the NSX 5 speed because the two boxes use the same case and the 5 speed can have beefier components.

quote Originally posted by Steven Snyder: I think the solution that would provide the best result is a different right side case altogether. This obviously isn't all that practical. I think the best practical solution would be to use a FWD bellhousing half (I think it has a slightly different design around the right side diff bearing to accomodate the half shaft bolts, unless the Fiero already has this) and bolt a reinforcing cage through the half shaft bolt holes, some bellhousing bolts, and the motor mount plate.

I have looked into this and I think the best way to do it would be to machine off the backs of the bosses into which the case bolts around the diff thread. Replace the case bolts with high strength threaded rod and put spacers on the bellhousing side so that a plate can be fit that will rest on the spacers AND the flange around the right CV joint. Tighten nuts on both ends of the threaded rod. The plate in question should be 3/8 - 1/2" thick, IMO. The plate could also be incorporated into an extension of the V8 adapter plate.

quote Originally posted by AnimalGT: flames4me, Were your trans AND motor solid mounted? I've personally seen 3 Fiero getrags break similar this. All were V-8s with a solid motor mount and poly (or rubber) trans mounts. It seems to me like the solid motor mount coupled with trans mounts that allow for more movement, would cause high levels of torsional stress along the axis of the trans where most getrags seem to break. Coupling the torsional stress from dis-similar mounts and the internal stresses of a high torque launch sounds like the perfect trans destroyer to me. But, if your motor and trans were both solid mounted then my theory is caca... Scott

I've made my opinions of solid and hybrid solid/soft mounting before, but I'll summarize again . TERRIBLE IDEAS. Solid mounting removes the capability of the powertrain mounts to cushion shock loading. Combining the two means that the soft mounted part doesn't get the support it needs and has to transmit its loading through itself to the solid mounted part.

By "soft" mounting, I certainly do not mean gooey rubber like stock... Polyurethane is a great material for this, as is has a limited amount of give and gives in an elastic fashion... more torque = more give.

back in the 80's pontiac used to break the getrags also with their super duty 4 cyl. , they made a girdle to hold the case together like has been suggested. they used webster gear sets and limited slip diff. along with quarter master metallic clutch. i seem to remember john callies saying they were making around 350 hp when they were having case failures. they were also dog clutch gears ( no synchros ) and straight cut gears ( noisy) .

i dont know the exact numbers, but a guy on cgp wanted to put a g6 6sp in a gtp. we did some reasearch and found that the trans as it stood was rated for sometihng like 280/260

you would destroy that tranny

get a full build from zzp. it will last forever with a warrenty

Everything I've seen about the G6 6 speed says that it's rated for either 295 or 300 ftlbs.

Straight cut diff gears would eliminate this failure mod be getting rid of the end thrust on the right diff bearing. However, the noise would render the car unpleasant to drive at best.

Still not understanding why there is skepticism about the 6spd with no known failures to date that I'm aware of and a considerably higher torque handling capacity relative to the Getrag which should yield a considerable benefit given how well a good Getrag stands up behind a V8. As Will stated earlier there is a difference regarding axle load distribution regarding the bearing and busching in the transmission, either it has been a while or I don't remember or just never discovered it having not built a manual tranny yet, I was surprised a second time while taking measurements for custom axles for the 6 spd when I some how rotated the pinion gear out of its proper position to the point where it elclipsed the bore and would not allow the axle to be inserted. The first surprise was forgetting that I had removed the bolts holding the shift mechanism in place and accidently pulled it out of the transmission.

The way I see it, the 6spd is rated at a max gearbox torque of 295 lb/ft in a 3525 lb car, so in my car at about 2750 lbs it should be rated at:

3525 / 295= 11.95 ft per lb

so provided F= ma and KE = 1/2mv(sqrd) still, one could reason the following, at least I will;

3525 - 2750= 775 lbs difference

775 / 11.95 ft/lb = 64.9 lb/ft

that I can add due to the weight reduction and henceforth load reduction on the transmission since that is what it would take theoretically for the lighter mass to exert the same load on the transmission under the same conditions relative to the heavier vehicle. 295 + 64.9 = 359.9 lb/ft plus whatever GMs safety margin is to insure 100K plus durability 400 lb/ft maybe for an appreciable non clutch dumping life? My rational is you're not going to kill a Getrag behind a 350 lb/ft engine in a honda civic as fast as you would in a bonneville.

quote Originally posted by jerry455: back in the 80's pontiac used to break the getrags also with their super duty 4 cyl. , they made a girdle to hold the case together like has been suggested. they used webster gear sets and limited slip diff. along with quarter master metallic clutch. i seem to remember john callies saying they were making around 350 hp when they were having case failures. they were also dog clutch gears ( no synchros ) and straight cut gears ( noisy) .

A Webster gear for the differential. The gear was still hypoid cut to match the gear on the stock Getrag intermediate shaft. They welded the differential bearing bores some and remachined the bores closer to the intermediate shaft to get a lower gear ratio final drive. From what I remember there was only one gear available. Provided a 4.30 or so final ratio. I think they used that with the 3.94 intermediate shaft. That is why GM ended up with a bunch of 3.94 ring gears but no 3.94 intermediate shafts years later. If it would be possible to make new intermediate shifts we could go the other way and have higher ratios. But it would be next to impossible to make the intermediate shafts. Ring gears could probably be made but not the intermediate shafts, at least not with out a considerable cost.

The other individual 1st - 5th gears were straight cut but not the final drive gears.

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Rodney Dickman

Fiero Parts And Acc's Web Page:
www.rodneydickman.com
Rodney Dickman's Fiero accessories
7604 Treeview Drive
Caledonia, WI 53108
Phone/Fax (262) 835-9575

The Getrag gears are "helical". Hypoid means something else and applies to bevel gear sets in the differentials of longitudinal cars.

I thought that the plug in gearsets that Toddster found had straight cut final drives? I tried to look up the thread, but the pics didn't come up.

Being that you have a V8 you need to talk with forum member Tina, i believe she busted dozen of isuzu transmissions then switched to a getrag transmission, she split the transmisison, sent all the parts off, had them cryogenically frozen for strength and got it back, she said after having that all done, she broke her FIRST set of axles, she said the axles lasted through the dozens of transmissions before, but after having the transmission strengthened up, the axles were the next weakest link, and yet ALOT cheaper and easier to replace.

matthew

I also bought a 4t65e-hd I heard all good things about them and they seems to hold the most with out breaking I was almost talked into the getrag trans I'am glad I didn't go for it......

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It's not over yet

quote Originally posted by chevypro101: I also bought a 4t65e-hd I heard all good things about them and they seems to hold the most with out breaking I was almost talked into the getrag trans I'am glad I didn't go for it......

good idea!

the autos put a ton less stress on the axles and you can run a shorter axle that is less prone to twisting.

KNOWLEDGE IS POWER BUMP!!!!

quote Originally posted by darkhorizon: good idea! the autos put a ton less stress on the axles and you can run a shorter axle that is less prone to twisting.

That's a bit misleading. Are you referring to axle twist or axle failure? A shorter axle will fail before the longer one will. They will both want to twist under the power, but the longer one can spread the strain out over a longer length and return to normal.

California Kid has run into this on his car. He's broken some axles, and it's always the short one that goes first.

Yes, the long axle is prone to twisting, but that makes it less prone to failure.

KNOWLEDGE IS POWER BUMP!!!!

oops!!! edit for the newbie mistake

[This message has been edited by BMTFIERO (edited 02-05-2008).]

quote Originally posted by Steven Snyder: You intend to weld a thin aluminum case and expect it not to warp? Once your diff bearing race moves out of alignment you're screwed... Also once you weld on aluminum you have to get it heat treated if you expect your welds (and the area around them) to be strong. The heat from welding anneals aluminum.

Not only that.............it's cast aluminum, what some refer to as pot-metal. Horrible to weld to, doesnt leave a clean line, and distorts the integrity of the cast. You'd be better off actually welding in gusset material.


To solve the trans woes. You'll need to look into one of those race transmissions that shift without a clutch. Or build the 4T65E.

Pot metal and cast aluminum are NOT the same thing.

The transmission case is NOT pot metal.

quote Originally posted by Will: Pot metal and cast aluminum are NOT the same thing. The transmission case is NOT pot metal.

Not exactly calling them the same thing, just referring that they weld the same.

I'm a little confused about the part where the wheels were pulling off the ground on the street with slicks???? The last time I ran slicks on the street it felt like I was on ice. They just spin. The track's surface is a different compound than the street, designed for the slicks to grip.
The only time I cracked my Muncie in my V8 was when my solid rear trans mount broke through the frame and the transmission twisted. No problems since.
Dave

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1987 GT (my toy-see above), 1987 GT (wife's toy), 1986 SE soon to be VR6, certified master technician/shop owner
www.njautobahn.com

quote Originally posted by Formula88: That's a bit misleading. Are you referring to axle twist or axle failure? A shorter axle will fail before the longer one will. They will both want to twist under the power, but the longer one can spread the strain out over a longer length and return to normal. California Kid has run into this on his car. He's broken some axles, and it's always the short one that goes first. Yes, the long axle is prone to twisting, but that makes it less prone to failure.

A longer axle spreads the strain but not the stress, which is what really breaks axles (or anything). It would be analagous to chain links. Theoretically, neglecting the weight of a chain, a short chain will carry exactly as much load as a long one. Realistically, as length of the chain (or axle) increases so does the odds of a material defect. If you apply a 300 ft-lb moment to the end of a 24" axle you will have exactly twice as much rotational strain (measured at the end) as a 12" axle. The stress, however, will be the same.

If anything I would expect this would have more to do with the geometry of the axles - the shorter axle having a greater angle off the centerline of the differential.

[This message has been edited by FastIndyFiero (edited 02-05-2008).]

quote Originally posted by PURPLE REIGN: Not exactly calling them the same thing, just referring that they weld the same.

So I am now assuming that all work is outsourced to someone else who is the welder that fabricates and welds the motor mount brackets and anything aluminum.

As a side note --------- ive had good luck with the proper aluminum gas welding rods on pot metal.

[This message has been edited by big block fiero (edited 02-05-2008).]

quote flames4me:... when you say 4t65e HD, what does the HD stand for?? thanks

Heavy Duty

quote Originally posted by FastIndyFiero: A longer axle spreads the strain but not the stress, which is what really breaks axles (or anything). It would be analagous to chain links. Theoretically, neglecting the weight of a chain, a short chain will carry exactly as much load as a long one. Realistically, as length of the chain (or axle) increases so does the odds of a material defect. If you apply a 300 ft-lb moment to the end of a 24" axle you will have exactly twice as much rotational strain (measured at the end) as a 12" axle. The stress, however, will be the same. If anything I would expect this would have more to do with the geometry of the axles - the shorter axle having a greater angle off the centerline of the differential.

Thanks for the clarification. Bottom line is, given an equal torque loading, empirical evidence suggests the shorter axle is more likely to fail.

The short axle fails, because for a split second there is less load on the longer passenger side axle due to twisting, and the rest of the force is loaded onto the shorter driver side, and it has less play and then explodes.

It might work that way if you were running a spool...

http://www.tripleedgeperformance.com/

good guy and a good sorce fot a well built 65e

Anything ever come of this? I split my case too, same way, at the track, 2000rpm launch and only went 10 feet(coasting) 3.4Turbo btw
but like I said any thing ever come of this, getting a getrag stronger?

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"DRIVE IT LIKE A FIERO"
'84 Fiero, engine to be determined
'87Blue GT 3.4L Swap Completed!!!!!!!! Boosted!!!!!!!
Las Vegas Fiero Club
Fiero Road Club Of Northern Nevada

quote Originally posted by Rodney: A Webster gear for the differential. The gear was still hypoid cut to match the gear on the stock Getrag intermediate shaft. They welded the differential bearing bores some and remachined the bores closer to the intermediate shaft to get a lower gear ratio final drive. From what I remember there was only one gear available. Provided a 4.30 or so final ratio. I think they used that with the 3.94 intermediate shaft. That is why GM ended up with a bunch of 3.94 ring gears but no 3.94 intermediate shafts years later. If it would be possible to make new intermediate shifts we could go the other way and have higher ratios. But it would be next to impossible to make the intermediate shafts. Ring gears could probably be made but not the intermediate shafts, at least not with out a considerable cost. The other individual 1st - 5th gears were straight cut but not the final drive gears.

I had read some ones thread talking about this concept ant thought it to be a good idea I could use. Before I put my Getrag onto my Northstar I made such a girdle plate for the diff side, I scavanged a Quad 4 diff and installed new bearings on it, cryogenically froze the gearsets, and tempered the case. Some details of this can be seen about 3/4 down the page of https://www.fiero.nl/forum/Forum2/HTML/089024.html.
As to welding o the case, be prepared to mill the faces if you do. I welded 1 relocated lug to match the N* pattern and the case warped a bit. It was not a big weld or a hot one either. The warp was encountered when I was having the diff bearings shimmed and a consistent shim measurement could not be had. A skim cut on the case fixed it up.
How does it work? Who knows! I have not busted it but a N* is not a torque monster, and I have not figured out yet how to get it running properly anyways - maybe someday.......

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Daviero - 88 N* GT

quote Originally posted by sardonyx247: Anything ever come of this? I split my case too, same way, at the track, 2000rpm launch and only went 10 feet(coasting) 3.4Turbo btw but like I said any thing ever come of this, getting a getrag stronger?

still down from the blowout, Im just taking my time this time and doing it right, building the car for how I want to drive it rather then just throwing parts togeather and hoping the hold togeather. there will be a very in-depth write up of everything I am doing when i finally finish it. So far I have the tranny (getrag again) built how I want, a new motor (SBC again) with a much different powerband, and many new little goodies that I will discuss later. I just need a custom clutch (still dealing with Spec to get one built to my specifications), and a few other minor parts. hoping it will be back at the dragstrip next season.

quote Originally posted by Daviero: As to welding o the case, be prepared to mill the faces if you do. I welded 1 relocated lug to match the N* pattern and the case warped a bit. It was not a big weld or a hot one either.

*Probably* this could be fixed by tossing the case half in your oven on "clean" for a couple of hours. Machining shouldn't be necessary.

quote Originally posted by flames4me: heres some pics that i promiced, there not the best quality, but i hope you get the picture. here is one of just the major crack... heres one of me trying to show that the tranny mount is totally separated from the rest of the tranny... heres the last one that i got, i tryed to show the broked, rounded off gears that are still inside...

You really did blow that sucker apart. You weren't the first to blow up the light duty trans. and you won't be the last.
High performance engine + slicks and a Getrag = shrapnel. With a built auto as suggested your problems will be solved but you will also need another adapter plate if its an early or late SBC configuration.

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87GT - 3800SC Series III engine, 3.4" Pulley, N* TB, LS1 MAF, Flotech Exhaust Autolite 104's Custom CAI 4T65eHD w. custom axles, HP Tuners VCM Suite.
87GT - 3.4L Turbocharged engine, modified TH125H
" I'M ON THE LOOSE WITHOUT THE JUICE "