[78novaman]

I have a '78 Nova Custom with a 250 L6. I have the service manual for that year and it tells me that I either have a THM 200(???), CBC 350 (??)or a TH350 3-speed auto trans. What the heck are the THM 200 and CBC 350? And are they any good. Or even better, how do I tell which I have (I'm almost certain it's not the TH350). Anyone who knows what these things are and comments would be greatly appriciated by me. I am planning a v8 swap and need to know if I am going to have to do a tranny swab as well.

[DoubleVision]

a th200 is a light duty tranny with a lower first gear than a 350, they don`t have a modulator valve, they shift by pressure. so that`s one way to tell, a 350 will have a vacuum line going to the transmission. a CBC350 stands for chevy/buick combined. but i know also the 6 cylinder version of the TH350 isn`t as beefy internally as a V8 350 is according to my transmission builder, so if it is a TH350, i`d have it beefed to withstand a high performance V8, but i imagine for a stock V8, it would be fine as is, stock 305`s came with TH200`s, so the application counts also.

[78novaman]

Thanks man, that helps. I'm, glad to hear that the TH200 was put behind the 305 because that's probably is going to end up in place of the 250. I was also unaware that GM used a universal bellhousing bolt pattern on thier TH350. I was under the impression that only the 200-4R and 700-4R had a few units produced that had the special bolt pattern.

[DoubleVision]

When I was in Tech College, I had a 79 Malibu Classic that had a 200 and I wanted to swap it over to a 350, my instructor said "don`t do it, the 200 has a 3.08:1 first gear and the 350 has a 2.52:1 first gear, the reason is because of a low power engine, and very high rear end gears like in the 2.23 or 2.73 area. you install a 350 and don`t gear it lower in the rear, it`ll be a dog off the line with that little 305 your running"
Also this was when i learned of a CBC350, which i think could also mean Chevy - Buick - Caddy, because we have a caddy 472 bolted up to one, but I don`t know if a buick and a caddy are the same pattern or not. I like these transmissions because they`ll accept a few different engines. which is good for someone like me who likes to sometimes try something different.

[chrome_ashes]

I think I would skip the TH200 if you have other options. I spoke with several mechanics and most were reluctant to even consider rebuilding it. It's my understanding that these trannys were pretty weak and parts are hard to find.