Help to locate transmission (Page 2/2) James G MAR 31, 10:25 AM Trinton. Found a 4T80 out of a 2004 DeVille with about 93k on it. Vin# 9 I was thinking a full rebuild, shift kit. Anything else you can recommend or what I should be looking for. Anyone's opinion is very appriciated. Thanks Trinten MAR 31, 05:37 PM I would say when you're putting together your rebuild kit, buy parts from Sonnax if your budget allows: https://www.sonnax.com/units/221-4t80-e Sadly Sonnax doesn't make a "sure cure" box yet for the 4T80 (it's their complete rebuild / improve parts kit they put together for other transmissions). I don't think you'll need a shift kit, you do need to modify the 2-3 shift piston (I think I said 1-2 earlier by mistake). Triple Edge performance had put a dual-spring assist under the 2-3 shift piston to ensure firmer shifts, my builder went a step further than that. I will mail you the spring setup that Triple Edge Performance installed for the cost of the postage. I'm not a fan of most "shift kits" because all they're doing is raising overall line pressure, and while that can introduce firmer shifts, it's also putting extra strain on other parts of the transmission for no reason, and can lead to other failures. This is a general rule, and everyone has an opinion on the topic. For every person that says "B&M shift kits blew up my transmission!" you'll get a person that says "mine has been fine". When it comes to putting high power through parts, I want to err on the side of caution and not introduce unnecessary stressors.