How much does it cost to rebuild an engine and transmission yourself?

It really will depend on the car. Most of the 80's stuff is getting rare and not many of the cars were popular so for the most part no parts are being reproduced so its used or old stock stuff which usually cost more than new stuff.

Transmissions for the most part are not a problem. Most people don't consider auto transmissions a DIY item. Carry one into a transmission shop and it will cost at least $1500. If you have a shop do it all figure on about $500 if its a RWD car and $1500 if its FWD or 4x4 for labor just to pull it and install it.

Engines if its a Chev V8, Buick 3.8/3800, or Ford 5.0/302 those engine can be done and found pretty cheap because they used them so many years and were all very reliable engines. Just about any other engine will start in the $3500 range. If you are going to do it yourself you will still likely have in the neighborhood of $1500 into machine shop labor for the stuff you just can't do at home. Parts cost will depend on the engine. You can get a rebuild kit for some engines as low as $500. Other will cost you $3000.

If you have to ask, you don't have the knowledge/special tools required to properly rebuild a transmission.

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A Pinto or a Lamborghini?

It really is a moot point because if you had to ask the question, I doubt you have any clue how to do that. I doubt also you have access to any of the special tools that are needed as well.