What EXACTLY are the weaknesses of the TR diff?

Reason I ask?

Because I will shortly be dropping the TR drivetrain out of my TR for maintainence. I have a very long history with beefing up offroad drivetrains, (cases/gears/CV's/shafts) to gain reliability in VERY severe conditions. So...................what is/are specific the weak points of the early TR differential? I would like to be able to beef-up, add reinforcement, stiffen, or what have you, to try an insure that the TR diff can handle the "everyday" stresses/demands that may be put upon it. Be aware that I am a driver that rolls into the "administration" of acceleration and gives consideration to the drivetrain being treated "properly". But I would like to feel confident that the transaxle case/casting etc. is the best it can be. If need be I will TIG/add re-inforcement to counteract loads which might be disaterous to the diff carrier......................Any suggestions or instruction would be welcomed......................Kerry

 

The two items that stand out, from what I have read,
The input shaft for the transmission is notoriously weak, called a "quil" shaft for reason. I believe there is a heavier shaft available but you would have to ask an expert.

The other is the welded halves of the carrier assembly on "regular" TR's hence the upgrade to the single piece carrier unit from the 512TR. The welds crack after a while and the carrier spreads apart inside the housing and on occasionly takes out the side of the differential housing.

 

correct, bad designed diff carrier. Who welds carriers together? A friggen pinto has a better diff.

 

So remove the carrier and re-weld/weld correctly would be an advantage...............Right?

Next.................Is there room/dimension to "enlarge" the input shaft? If so, then I can machine a larger diameter shaft, including the dimension of the splines/crank input, etc...............MAYBE................(if this is a factor) .........................Best probably is to get the parts in hand and observe what the fitment dimensions are..........................Thanks to all for the insight.

If it is a case of the "welds"...................then this can be resolved......................My experience in the offroad world is that welded diffs work.............But....................one piece diffs are a much stronger choice. OR...... if the costs are preventative to actually setup and machine a complete new diff component, it may be better to just beef-up, weld, whatever the hell, out of the exsisting diff components.

Again any suggestions that members can contribute to make the diff a
better" piece is very much welcomed.....................

 

There's a shop in Australia that makes it right, did you get a new one, Newman? Or, they finally changed this design in the final 512TR I think.....

Check with WILLIAMH and his racing TRs, IIRC you want the input shaft to shear as kind of the 'weak link"...anyway his racing TRs are WAY pumped up so whatever he did should be fine for street applications of stock tires.

HTH

 

I havent changed my diff carrier but ill certianly have it in my hand when I do the engine out service along with the sodium filled exhaust valves. Chances are all of the above will be replaced.

Re-welding the carrier wouldnt be my first choice, probably fail at the edge of the new weld. Upgrade to the 512M or modena engineering in austrailia's one piece unit that will never break. The weak shaft acts as a fusable link in my opinion, toughen it up and break something else more costly. Just dont do hard down-shifts that chirp/lock the tires and you wont break it.

 

If done correctly................Should not be a liability, would be a point of "confidence"!

I agree with the fusable link theory................

 

Is a schematic available for the stock diff carrier? I'm having trouble visualizing the assembly inside the transaxle.

 

Would be helpful.................................But again, I must say, I drive my TR with some "abandonment".........................but I roll through the starts and I treat it as a high end, high performance, exotic automobile......................not a 68' Roadrunner and looking to waste the 64 GTO with a six-pack in the other lane. I just wanna give it the **** and cruise at 100mph on the interstate and grin...................Now seriously are there any detracters of this goal? ..................

 

its not so much pumped up, it has a little over 500 hp w the motronic injection, its more the abuse the trans gets from full throttle acceleration ALL the time. She lives at redline

There is enough room to upgrade to a 512M so there may be a little more room to add an even bigger one

 

Exactly,

as for the sodium filled valves, if those things ever explode they can seriously damage your engine

 

i thought the sodium valves ended with the 2v carb cars? as in the i thought the Qv 308 series and all the injected v12's from the BBi and on had solid valves. thats insane if a TR has sodium filled valves too, i will never buy one of those, given the costs and weakness of the trans axle. hell i would rather have 2 "lesser" cars for the money, and find another 308 "whatever".

do you know for a fact the TR's have sodium (exhaust) valves ? !

 

The TR doesnt have sodium valves to my knowledge, nobody said they did. The boxer does though, which is a 2V engine. Even though the boxer engined cars have the potential to have a diff break, the fun out-weighs the "safety" of driving 2 308's instead. I cant go back now that Ive experienced the boxer sound/feel/torque, the list goes on.

 

Shop that did my work explained the input shaft is kinda mechanical fuse to prevent damage. And any weld process creates a heat affected zone that weakens the part. So just buy new. The shop was Francorchamps in Calif. and they did a couple of these a week and even made better gears. FWIW.

Jeff Pintler
89 348tb, 86tr

 

If someone has an old diff. carrier laying around I can put it on our CMM (coordinate measuring machine) to get all the dimensions and then do a cad drawing of it. I have considered machining one too, but it would be easier to get the info ahead time and then do it (reduce down time).
John

 

Oh what the heII: Anyone have a line on an F512M differential and hangers??? Been searching for one for almost 2 years!

 

Dear Ferraristi,

Newman,

Just think how much fun you would have if you upgraded that boxer to a Testarossa... if 2v are good....4v must be better !



Shamile

Freeze....Miami Vice !

 

Does anyone have a picture of a broken TR diff and maybe also a picture of the "better" 512TR/M diff ?
Would like to see some pictures before my diff / gearbox will be removed during this year winter.

 

I did a thread a while back. Billows of White Smoke (or something like that). It had pics.

 

Thanks for the hint. I only did a search in the TR section before. The thread shows pictures from the cracked housing parts. Do you also have pictures from the diff itself ?

 

I went to the tech session at Classic Coach, NJ. They showed me the parts of a broken one and said that they had a process that would reinforce what breaks. (Sorry, I am not more technical than that).
Has anyone had it done?
I asked Carlos for an approximate price, but he has not gotten back to me yet.

 

Just to add what we have seen over the years on both stock and turboed Testarossas I have replaced more cases than diffs. The only diff I have ever seen fail was slid into a curb. I have also replaced more ring and pinions than diffs, one TR and one 512 TR. We have replaced many propeller shafts of the early style. As noted by others and for the same reason we run the small shaft in all the turbo cars we build for the 'fuseable link' reason. On the cars we ran the 512M shafts in we just started snapping off the snout of the main shaft. In my experience there is no one weak point other than the early propeller shaft on a car driven on the street. On a car with big sticky tires on the track it is a different story, look to the BBLM cars for info on that as the transaxles share the same architecture. We have seen a near equal number of 2nd and 3rd gears have the teeth pulled off as we have seen mainshafts fail and ring and pinions and cases. All those failures out number the failures of the welded diffs by a great number. I believe that tire selection and condition, chassis set up and mostly driving style dictate when and what will fail in the transaxle.

 

Thanks for sharing your experiences and percentages. It all sounds quite logical the way you put it, in essence, "Get rid of one weak link and you create another"

I had some hesitations in buying a TR because of the input shaft and carrier issues discussed in numerous threads here. I decided to gamble on the one I have due to it's previous history (or non-history of hard use).

 

I also think that the type failure may be related to where the car lives. In Texas we don't have a lot of winding roads to drive, more strait highway stuff. I think a car that lives in the mountains where there are tight curves and is driven hard on them may have a greater likelihood of diff failures but I have no real basis for the reasoning other than speculation.

 

Mine lived in Arizona until 2005