cagotzmann

I have just pulled my TH350 from my 1978 corvette. (leaking fluid) so I would like to know what I should put back in. Fix up the TH350, replace with a 200r4,700r4,TH400. What mods work best, shift kits etc. I want to be able to manual shift as required and also it needs to be rock solid and not break down shifting. I considered switching to a manual but I dont think there is much difference when you only use 2 gears on the road courses in my area (canada).

TH350 2.52 1.52 1.00
TH400 2.48 1.48 1.00
200r4 2.74 1.57 1.00 0.67
700r4 3.06 1.62 1.00 0.70

Seems the TH400 has the best 1st ,2nd gear for road racing.

Your thoughts ?

What about the torque converter stall RPMS works well ?

Supercharged111

400 is a pig, my vote is for the 6L90E but that'd be a pain to swap in. Why not swap in a manual? You could have an overdrive when you're not on track, plus the gear spacing would be better. If you stay auto, a stock stall is best as it cooks the fluid less and, IMO, responds better and gives better resolution. High stall is only good for a launch.

cagotzmann

I thought about changing to a manual but the cost + modifications required + not much benifit road racing. The track I drive is a 2 gear track. Using a 5 speed would be 3rd and 4th gear. So a 1.3 + 1 ratio for a manual vs a 1.51 + 1 with a TH350. Yea the 6L90E would be great but as you say a pain. I may consider changing the rear axle to a 2.73 to make 1st somewhat useable on a road track.

DaveL82

If you're staying with an auto I'd go with the 200 or 700r as the changes should be minimal. Pick the one that works best with your rear gearing.

I went with an old Doug Nash 5 speed when converting from an auto. To fit the box in was mini.all work but changing out pedal box was a real pain. Box works great with my 80 model 3:07 gear. If I need a new box I'll go with a 4 speed as the car is mainly for track days.

Kevova

A powerglide, fairly bullet proof, light, takes very little horsepower to run in high gear. Of course rear axle gear will need to be changed

Rob31

I have a good , stock 700R4 sitting here .