I'm having a 455 built and my TH350, as well. I'd like to achieve 1970 Stage one numbers from the engine. Can a turbo 350 be made to handle the torque? I'd rather stay with it if possible, as I'd like to change as few variables as possible. I'm converting from the stock 350 motor to a big block. Thanks!
If it's stock and has lotsa miles it may not last. If you use as cooler, the right stall and rear gear combo, that would help. Do you plan on racing or cruzing?
TH350 is a lightweight/light duty trans. If you plan on doing any racing or some serious street use, get a TH400 shortshaft. Best trans ever built!
While the 350 trans was originally intended for the lighter duty applications, it can be built to withstand more power than most people think. For example, Greg Gessler has one in his 1972 GS Stage 1 car that ran 11.0s @ 127. I've seen folks at our local track with some really fast cars running the 350 trans. It takes slightly less power to turn the 350 and it is a few pounds lighter which is probably why Greg runs the 350 in his car vs the 400. If your 350 trans is stock and has high miles it may or may not last. If I were you I'd run the current 350 trans and see what happens, if it breaks you can then upgrade.
I have a friend with a camaro with a blown sbc, car ran 9.6s at 142mph. Never quite got it to hookup, never had a problem with the th350 tranny. Jeff
The TH-350 is a great transmission. I had mine upgraded before installing the 455. Have the the weak components replaced and have it rebuilt by someone who knows what they're doing and you will be very happy with the results. Also after the 455 is in, get your shift points set-up so they are done automatically where you want them rpm wise, there's less stress on the trans. this way.
GM built a HD version of the THM-350, called it the THM-375. I believe it had extra clutches on the 2nd gear engagement, for increased torque capacity. They put them in big cars starting in late '71, sometimes behind 350's sometimes behind 455's (later years). I'm pretty sure any THM-350 can be made into a -375, I'll bet there are trans shops doing this without knowing about the -375 version. :laugh:
I'd love to build a strong TH350, something that would handle 550-600 hp all day long! :Brow: Just don't know what componets it would require to handle that kind of torque and HP. Maybe a good knowledgeable race tranny guy will chime in here. Jim
Good question - I'm no tranny expert, but I'm pretty sure, because: 1. My '72 Chassis Manual shows the THM 375 to be a HD version of the THM-350, and the THM-400 to be a whole 'nother tranny. 2. The tranny in my March '71-built, '71 LeSabre (350 engine) is externally identifiable as a THM-350, but when I had it rebuilt (known first time), it had the same number of extra clutches as the THM-375 had. Apparently, is was a late-enough year car to get the HD tranny. o No:
FWIW, I'm leaving my rebuilt-with-shift-kit TH350 behind my 455, which is a 70 model advertised at 370/510. I'm not the least bit worried... (I wish we had a "fingers crossed" smilie...) Frank
