John Veninger

Back in 2007 the new stroker motor destroyed the shafts that hold the spider gears in the LSD during the Sebring race. I rebuilt everything, including cryogenic processing all of the gears and shafts.
https://rennlist.com/forums/928-foru...uild-able.html

Fast forward to 2010. I heard a bit of grinding/rattling at the last event and thought it might have been a lose exhaust. I did notice shifting wasn't the same.
Packed up and put the car away for winter. Decided to drop the trans.
Nice surprise...not!



In the process of getting an 89GT 5 speed. Will swap out my current LSD into the GT box since it was rebuilt and has a higher lock.

Would love to fix this one as a spare. 5th is gone and I have a few minor chips on 4th.

Mrmerlin

thats a bummer.
what kind of oil are you using ?
do you have a trans oil cooler?
Mark Anderson has similar issues I guess you have talked to him about the 5th gear issue

John Veninger

Redline 75w-90
Yes, oil cooler and temperature gauge.

That gear is just not happy with the big sticky tires and tones of torque!

SeanR

Man, these things are going to be real hard to find when I finally get around to wanting a 5 speed box.

Benton

John, is the return oil entering the diff at the fill plug or do you have it setup with a sprayer/spray bar?

Rob Edwards

John, is that a GT or a GTS box? I just put a GTS 5th gearset on the shelf for a rainy day, both GT and GTS 5th gears are still available new. The GTS set was $710ish, comes with the internal needle bearings and a new synchro too. For whatever reason the GT 5th speed is significantly more, like $1200ish.

John Veninger

Return into diff. No spray bars. The temperatures have been OK.

John Veninger

89 S4 box. Final drive of 2.64
I think I could use a 5th from an S4 box, just not sure. Haven't looked at part numbers closely.

mark kibort

how much torque do you have john.

the 420ft-lbs seemed to be a problem for my transmission too, or it was its time after 10 years of all out racing, full seasons. however, maybe 320rwt is ok?
that could be the problem for short shifting the strokers, you end up at max torque and that might be too much , plus the shock load if the shift iis too great. keep in mind, the higher grab after market clutches could EASILY be the reason for failures. upon shift, the loads can go up by 20-50% depending on the shift style . something to think about

that picture looks like my 5 gear with the holbert. however, it was making noise for 2 prior weekends. (noise in neutral) what ever the noise, it was the beginning of the failure that took out 5th. no other gears seemed to be hurt.

Tom. M

Lizard, amongst his many projects, has tossed around the idea of a 928 box with different internals... I suspect if the GT/GTS boxes become non-existent, this might become feasible...
Otherwise...John..you might just have to switch to an AT?

John Veninger

Over 500.....

No way!. I'll just put in early transmissions and try and get a weekend out of them

I have a complete 83 box without a diff in it. Might try and sell that to fund the new GT box coming.

Mike Simard

I guess I need to chime in on this.
I think I have a fix for these input shaft (aka 5th gear) problems but it's hard to quantify.
Call me if you want to know more. It's a couple of parts that install fairly easily. I suspect if I post all it about it, it will be copied and be all over RL and RW. I hope everyone understands.
So far I've had half of the fix on my own car and nothing's broken. Someone else has the same thing on their car and they can chime in if they want. I just finished the last half of the mods but haven't been to the track yet. I could be wrong but I have a high level of confidence in my own gear/shaft not breaking, it's one of the few parts of my car I can say that about

mark kibort

Why not have a spur gear set made for 5th. why do you need a helical geal for 5th input?? noise? 100k mile longevity? seems the spur gear would be a lot stronger for jerk forces.

mark kibort

JV, how hard was it to rebuild the tranmission, if nothing else needs to be touched but the 5th gear set?
Do you think I could do it if I got a few of the required tools that didnt cost too much? (or used a press from the shops to do specific disassemblies)

90 S-4

Mike Simard you have a PM