This trans originated in the early 90s and was used behind all of the Northstar engines, even the Bonneville GXP. There are tons of them out there ready to grab and they have a 1" chain stock with a much nicer sprocket setup They are big and heavy and so are the internals. I bought a 97 GP last year cheap to build up a parts-breaker, but when the 1" chain sets for the 4T65Es went extinct I pushed it aside to build up because I cant do the testing I would like if I dont have a chain strong enough to work on the rest of the trans. The 4T80E has potential BUT fitment is a chore from what I was told from SDD and they too were working on putting one in a GP. They already fitted one in a Riviera and he told me about everything that had to be done. The real question is how much power can one of those take in stock form, hardpart wise. The torque converter is different but I can have custom ones made so that is a non issue. The axles are another issue because the 4T65E ones wont work. They were made for bigger and heavier cars with a factory 300HP engine, so factor in taking an easy 500-1000lbs of weight off and a few tweaks and the trans should hold up pretty well but until testing is done its hard to say anything. The beaty is that there are plenty of these cores floating around if the hardparts in stock form are up to the task then you can cross that much money off of a build compared to a 4T65E, but this trans wont work with the LS4 cars which have really started to pop up lately in the higher powered arena since they are starting to get a few years on them.
