Rebuilding the [stock] tranny in my '75 was one of the first undertakings I had with this resto project. It was done months ago; but today I was cleaning up the garage as my tools are scattered everywhere and I can't keep track of which one I left where. Low and behold, guess what I found- the roll pin that fits in the end of the drive shaft that holds the castellated nut in place. Sometimes the simplest things to do are the easiest to forget.

So, before I go tearing the rear cover off, I rememered reading somewhere that the paper gaskets affect gear meshing depths and that you should only use the same number of gaskets putting it back together as there were tearing it apart. Now if I'd been smart, I would have kept the left over gasket I had from the original rebuild kit I bought. But I wasn't so smart.

So is there any truth to that statement? Or can I just tear off the rear cover, install the roll pin, and goop the damn thing and be okay? It wouldn't be that big of a deal to just shell out the extra $30 for a new kit, but if I can just goop it and be okay then there's no sense in waiting for it to ship.

Thoughts?

The rear cover gasket isn't critical, it's just there, and there's only one thickness. The gaskets between the housing and the intermediate plate are CRITICAL. They fine tune the pinion depth and MUST be correct. If you didn't replace the old ones with the EXACT set, you're pretty well screwed, and will have to get someone with the correct tools to determine the correct pinion depth. There IS NO OTHER WAY. The Cap'n

I only somewhat agree.

True, the rear one is no big deal. If you just did the build then you should not have to worry about a leak when you reassemble. NO GOOP!

The gaskets that are between the intermediate plate and the tranz housing are critical. You do not count number of gaskets, you measure thickness of each gasket and replace with comparable size. The best place to measure the total gasket thicknesses is at a point where they are not compressed - where there is a void in the plate. This thickness will give you the best reading for the stock setting. Where I differ with John is in the "your pretty well screwed" sentiment. While the most correct way is to replace the gaskets with exact thickness replacements, it is totally possible to throw all of the gaskets, or some combo to split the error difference on from a seal kit and have it run fine. This sounds like heresy, but I have had people do it many times and NEVER had a problem with it (if I didnt see it I would not believe it either). There is a reason that the right way is the right way, it gives you the largest margin for a positive outcome, but the other ways still have a pretty sizable margin for a positive outcome.

Remove the cone, replace the pin, put it back together with no goop and see what happens. If it doesnt work, you can go from there.

Keep us posted.

That's all well and good, except there's no chance in hell that I'd be able to get a measurement of the thickness of the old gaskets since they've already been replaced. I know for a fact that there was two gaskets between the intermediate plate and the housing- it was obvious when I tore it apart. So that's what I put back on it from the kit I bought from Pelican. But I checked with the PO anyway, and he tells me he never had the tranny rebuilt. So assuming that the gaskets were original factory, what measurement should I have on pinion depth? If there's numbers or something I need to get off the tranny to find this out, no problem, just lemme know.

As for gooping/not gooping, it'll just be a matter of time on that. I've got a long way to go before the engine and tranny go back in the car. But I'll go ahead and try to tear it apart w/out damaging the new gasket I've installed- if I can do it successfully then I'll still have a gasket and won't have to worry about goop.

It's not that simple. Every set of rearend gears (ring and pinion) is going to be a slightly different tolerance. We're talking in thousandths of an inch here. Every set has to be measured, and will have a different measurement. This measurement must occur on every set, even at the factory. In a 901 transaxle, to bring it into the proper specification, different thicknesses of gaskets are used.

So Docevil is saying that you may have come "close enough".

Does that help?

He is Gint the Communicator and he is correct

Not really... but thanks for trying.

I guess for the time being I'll just pull the rear cover, install the pin, and let it be for now. When I actually get the motor reinstalled and get the car running again, I'll keep my eyes and ears open for any signs of trouble. I inherited 2 spare tranny's when I bought the car, so if this one blows up I can at least start in on another one.

Thanks for the advice guys. I'll be sure to let you know when the tranny locks up and the car does a backwards asia moonsault through the air.

It's not that the tranny will "blow up" The pinion depth will be either too deep or not deep enough, unless you got lucky. Incorrect pinion depth can/will cause excessive wear and noise. Once the wear is there, it's permanent. Once it's noisy, it'll always be noisy. Wear causes the noise, and it can/will eventually lead to failure of the ring and pinion. Mind you, there may be a substantial lifespan before catastrophic failure, it it indeed fails. Or maybe only a short one. The noise can make you crazy. Look at me ............ The Cap'n