i recently bought a camaro with a 700r4 tranny... and im thinking i will replace it with a TH350 or a TH400... what would be the best transmission to put in an 89 rs camaro with a chevy small block 350 engine?

any input is appreciated..

 

The th400 will hold the most power, but as long as you're under 500hp/400rwhp I'd use either the 700r4 or th350. Personally I'd stay with the 700r4. A well built 700r4 should run about $2500 to do including converter. It'd cost roughly $500-$600 just to convert the car over to something other than the 700r4 and I feel you loose alot of streetability. I've used a 700r4 for quite a few years, but have been making too much power to use it the last 1.5 years. The th400 I have now is great at the track, but sucks on the street from no locking converter or overdrive. With my 4500 stall the motor is basically always reving at least 2500rpm at really any speed where it'd be at 1300-1500 with the 700r4.

 

I bought my car with a 700R4. I swapped in a TH350 after the first year for a better gear ratio and I didn't need OD in a race car. I then swapped in a TH400 because a transbrake for a TH400 was a lot cheaper than one for a TH350. After having some problems with the TH400 and I wanted to shave off more weight, I swapped in a Powerglide and never looked back.

At your power levels, a TH350 will do fine. If you feel you need an overdrive, try using a 200-4R transmission. It has similar gear ratios as the TH350 and has an OD.

The 700R4 is a great street transmission. The low first gear with a highway ratio in the diff still allows for quick acceleration and the overdrive with the highway gear ratio in the diff offers good fuel mileage. The downside is the low first gear and the wide spread between first and second. At WOT, the rpms drop too far down on the 1-2 shift. The low first gear with a performance ratio in the diff can create too much torque and can quickly overpower the wheels.

The best diff gears the third gen V8 cars got with a 700R4 was 3.42. It's hard to suggest the best transmission or diff gears without knowing your goals with the car.

 

If you want the overdrive for gas mileage and the lower rpm's on the freeway, the 700R4 will hold up to an easy 550-600+HP when setup correctly. The 9.5" lockup torque converter will not lose as much rpm as the stock torque converter on the 1-2 shift. So this won't be a problem here. If this a daily driver, then use 3.42's or 3.73's.

 

Street car id stick with 700r4
Racecar TH400