Ok. Chevy trans has a different hookup than olds for Speedo gear. I assume I can simply swap tailshat housings to fix that. Also the Chevy has a tiny vacuum modulator and the olds has a huge one. Is it possible the Chevy needs the smaller one due to the stage 2 build or can I simply swap that over as well?

 

The biggest difference is the bolt pattern on the bell housing. Unless you have one of the rare dual bolt pattern 350's you will need an adapter plate.

 

Yes I have he adaptor plate. Having trouble getting the original alignment dowels out of the block but other than that have that part covered. Just need to know how to proceed on the other two issues.

 

Use the modulator valve that came with the chevy trans.

What did this trans orginally come in? Model year,car/truck etc? I'll try to help. I don't see changing the tail housing is going to help you much. Just too much trouble.

I'm going to be blunt here, but I don't see trying use this chevy trans is going help you meet your goals. I get it, it was a good deal, but after dealing with the many issues like this, you're better off with the correct olds transmission and less headaches. Sincerely, I don't want to sound like an ***.

 

The trans was in a early 80' grnd national. Or is frshly rebuilt stage 2 with stronger internals and a shift kit. A friend had it and no use for it and I Got it for 600 bucks. The stock tranny in our car is worn out and needs rebuilding badly. Money wise we are at point of no return honestly for now anyway. Some st we will go to an OD tranny but have to make due with what we have for a year or so.

 

If you have a chance could you post a pic of the trans tail where the speedo hooks up? Lets see what your working with. With that, maybe we can suggest an adapter.

 

Doesn't the early 80's Buick Grand National 3.8 use the BOP bolt pattern? No need for an adapter plate if going in an Olds.

 

I couldn't agree more. The OP is obviously dealing with something else other than a buick tranny.

 

I apologize it was a Monte Carlo not a GN. It is for sure a Chevy trans. I will get pics of what I'm talking about here in a little bit.

 

Leave the modulator alone. Can you just change to a chevy cable?

 

I assume I could? I have the trannyss sitting side by side on the floor so figured it would be quick and easy to just swap the tail shaft housings over real quick. I don't know what could be different between them. That's probably what I'll do.

 

Swapped tail housings and drive gears. Problem solved. Got Leary about this motor so pulled apart and now have way bigger issues to worry about lol.