The Official 356Talk Forum

First I would like to make sure that the piece is of this... iteration of the transmission, not some crap left behind by whoever messed with it last. I don't know whether I can check the ring bolts without significant disassembly.

As to trusting it... Drove about 600 miles with zero issues, which is no real indicator if I have a bolt backing out. I know it is more reasonable to do it, but time is scarce.

Darn. I have to do it.

I had some time to flatten the parts. I'd say ring bolt retaining plate?

Yes.

As usual you're right Vic.
I went magnet fishing this morning, and got a bolt head out.
I wish I could go faster, but with a full time job and other occupations, time is regimented for everything. Still, I am ordering a seal kit for the 644.

Sorry to hear that, but at least no more damage was done. The left side differential cover was probably machined by the bolt head; you might have to replace that. No problem; same part for all tunnel-case transmissions.

Yes I feel lucky so far. Now to get the left side plate off. There is also a broken stud there that I will change.
Some real artists were in there last...

Got the left side cover off. Glad I listened to you all. Of the 6 ring bolts, one is broken and 4 others are loose. There is sign of movement on every one.
The cover has some damage, but doesn't seem too bad.
Now to order some parts.

I would replace that cover; it's pretty thin where it was machined by the bolt. There are many out there; should not be expensive.

OK, I'll look into it as well.

I think I know why it went pear-shaped: the bolts are grade 8.8. Insufficient there? shouldn't they be 12.9?

George Krompecher wrote: ↑Mon Feb 06, 2023 11:15 am I think I know why it went pear-shaped: the bolts are grade 8.8. Insufficient there? shouldn't they be 12.9?

Or 10.9 ?

Are they all 8.8?
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I think 10K or 12k was original, they didn’t use the 8,8 marking back when the car was new.

Yes all 6 are 8.8. All but one were loose, and all have damage from movement.

Tech questions:

Is it a good idea to safety wire the ring bolts, seeing how one got loose, or are the plates with correct grade bolts enough?

Loctite 270 on the bolts?

Edit: Next question: Gearbox in the car, engine out. Left cover off, right cover on. How do you block the diff from turning when torquing the ring bolts?

First, I would suggest removing the differential to check the housing for cracks.
Those plates were not a good idea; soft steel, easy to deform and loosen the bolts. The later bolts have a groove for a retaining plate and no washers under the bolt head. The retaining plate does not "lock" the bolt, but keeps the head in place if it breaks. Loctite; YES. And the correct torque for the later bolts.