I have a '78 TH350 and am getting a 700R4 from a 92 Iroc. Which tranny is going to be better? I currently have the stock 2.27? rear gears which I am swapping out with 3.42 if I use the 700R4.

If the 350 is a better tranny what gearing should I look into, to get about the same perfromance out of it? This is mostly a weekend driver and will be at the track on occasion as well.

I have heard that the 700R4 that I am getting is a really good tranny and it has been recomended that I install that instead of the TH350.

 

Since it mostly for driving and not for the track, you definitely want to go with the 700r4. Its overdrive will make highway driving a pleasure.

The 350 can handle more hp in its stock form but if you aren't topping 350 hp then the 700r4 is fine.

I can't make out what your current rear gears are. If they are 2.73s then go ahead and change to the 3.42s. But if you have 3.23s or 3.27s it is a waste of money to switch to the 3.42s. They are just too close to see a difference for the money.

 

Its the torque that will kill a tranny, and the TH700R4 will take up to 450ft-lbs in stock form.

Forget about the TH350. It's a different length and will just be a hassle to install when the OD tranny will be your better choice anyway.

 

in addition to the above info. the 700r4 has a steeper first gear ratio(3.06) where a t-350 has a 2.52.

this will allow your car to launch harder, specially with the 2.77 rear end.