Where to find stretch bolts for the Simplified diff?

[RetroSC]

I know the issues with the simplified differential and that it needs to be properly updated, but I really have no time for that project right now. So in the meantime, I'd like to just repalce my stub Axle bolts to get me through untill next winter. Easy enough, except I can't find them anywhere. Any help?

Thanks, Bill

[randywebb]

tried Stoddards?

[RetroSC]

Good call! I'll try them tomorrow.

[Grady Clay]

When you go to install the new bolts with the tits on them – remove and replace them one at a time. Do not have both out at the same time. With both out the differential shaft can slip out of place and you not know it. Bad things then can happen.

If you suspect the pin is out of place, you can remove the differential side cover and then remove the differential. Once you have the differential on the bench with both axle flanges and bolts installed, remove the flange on the non-ring gear side. Now you can reinstall the differential in the transmission with the ring side flange still attached. Next install the flange and bolt on the starter (non-ring) side. Now you can remove the flange on the ring side and reinstall the cover plate. Finally you can reinstall the ring side flange and bolt. PITA but necessary.

If you remove a stretch bolt and find the tit worn off, find the broken part. If it gets floating around in the transmission it will do damage. If the tit is still in the differential shaft the new bolt won’t fit.

Remember to replace the CV bolts and Schnorr washers. Re-torque the CV bolts after some driving.

Best,
Grady

[randywebb]

Ummm... if you are going to put in the pin instead, then how do you do this so it won't slip out of place?

and... any tips on doing the fix (complete fix) while the trans. is still in the car?

[Grady Clay]

Randy,

I think Pelican RetroSC has a 902/02 transmission which is standard for RoW ’67 911S. It has the “Simplified” differential and he wants a quick service replacement of the stretch bolts with tits.

Before the proper fix I replaced these bolts at every opportunity. This was even part of regular service and we kept track of how many miles the bolts were in service. True to form a mechanic took both bolts out, the pin slid out of position and locked up the rear axle. He discovered it and no damage was done. This is how we developed the procedure.

As soon as the proper fix came out we updated all of our customer’s cars. The devastation caused by this seemingly simple tit wearing off is amazing. The differential housing is broken, the pinion severely damaged, the input shaft in three or more pieces and the main casting destroyed. I have even seen bent center of the clutch disc.

When you do the complete fix you have the differential assembly on the bench. Once the armature, role pin and threaded pieces are installed the differential pin is restrained from moving out of position – no risk.

What I was addressing above if, with the original system of tits on the bolts, you remove both stretch bolts simultaneously there is nothing to prevent the differential in from falling out under gravity if positioned that way. There isn’t any to tell the orientation.

I agree it would be best to do the proper job. Yes it can be done without removing the engine & transmission.


One thing about this very important upgrade that hasn’t been resolved to my satisfaction is the exact part number for the proper threaded piece. I have spent hours on PET and with my original paper manuals. I am not sure of the correct number – yet. I would really like to find a copy of the ~’71 service bulletin.

Best,
Grady


EDIT addition in bold above.

[randywebb]

- I'm still not tracking how to do this complete fix w/o problems with the trannyin the car (see below). But I don't want this guy's thread to get too far off topic, so I'll copy some of this info to another thread. - Randy

"
When you do the complete fix you have the assembly on the bench.
* * *
Yes it can be done without removing the engine & transmission.
"

[RetroSC]

Thanks Grady, Great info!

Just curious Grady, but what kind of safe mileage can one expect from a new set of bolts?

[Grady Clay]

Randy,

Actually this is an appropriate thread. I know this is on interest to you. Perhaps you could post here all the links.

Does this help?
“When you do the complete fix you have the differential assembly on the bench.”
I edited above.

The issue about having the transmission in the car or on an engine stand is all about cleanliness. I am anal about cleanliness when repairing Porsche transmissions – for good reason. One grain of sand (silicone dioxide – very hard material) circulating with the transmission oil can be very destructive. It causes all those beautiful Hurth, ZF & Getrag gears and parts to prematurely wear.


RetroSC, Your question is difficult to answer with any certainty. At 6K mi most were close to new (but replaced anyway) others were frighteningly close to failing. I ascribe it to driving on snow (or other) where there is a lot of differential action. There is only rotational wear on the tit is when the wheel speed is different from the differential housing. You have to remember these cars were almost new then and many were driven from Denver to Winter Park, Vail and Aspen every weekend during the winter.

Best,
Grady

[randywebb]

Grady,

It sounds like you need to remove the differential ...

If you do that, do you have to reset all the clearances with special tools? Or is that only required to be done if the diff. itself is taken apart?

Thanks!