I've just finished a 455 motor rebuild and now it's transmission time. The trans came with the motor and I dont know anything about its history. It has no obvious leaks at front or rear seal or pan and that's all I know. And, tho ive rebuilt a few manual trans, I've never been inside an automatic.

Should I just change the oil and bolt it up and hope for the best, or should I do something more?
Like drop the pan and change the filter?
Replace front and rear seals?

Thanks for any advice.

 

At a minimum drop the pan, change filter & oil.

You know year of the 455 engine? Know year model both engine & transmission came out of? Is it a matched engine/transmission?

 

If no obvious leaks i would do like you said, fluid and filter and see how it does. You may get lucky and have a good running trans or get a better idea of what it needs.

 

The motor is a 71 and I'm jot sure how to decipher these numbers.

 

There are numerous threads on this site demonstrating confirmation of engine + transmission (matching numbers) you can search for and view. I'll simply toss up some images to assist you in evaluating if the trans was mated to the engine when it left the factory & your engine + trans. match. You stated the engine is from a 1971 vehicle. You can view the VIN derivative pad on the block then look to see if the trans. VIND derivative matches the engine (block) derivative. Images are self explanatory (I believe). Note the last six digits of the VIN derivative - do they match or not match?



Engine block VIN derivative


Note location of a THM400







VIN on dash, matches VIN derivative on block and VIN derivative on TH400

VIN derivative on a THM350

 

1971 BC code is from a Buick full size. I suspect it has a long tailhousing. At a minimum I would replace the front and rear seals. Probably get a new converter before you put it in.

 

Ah well, Joe has you covered....I have a couple fuel filters to change on my truck.