Iv'e been thinking about picking up a used 700r4 to put behind my 350 sbc-290 hp. I've got 3:08 gears in the rear. Would the difference in acceleration be worth the trouble. I know what needs to be changed. Just wondering if it is worth the time and effort.

Thanks, John

I wouldn't do it as much for the acceleration as I would for the overdrive. But since we're on the subject, your acceleration will improve as your 1st gear will now be comparable to a TH350 with a 3.74 rear end. Your 2nd gear will now be comparable to a TH350 with a 3.28. All that aside, you'll love the OD

I wouldn't put an Overdrive transmission in a car with only 3.08 rear gears. Your RPM's will be too low. The cruising sweet spot is usually between 1800 rpm's to 2200 rpm's. Overdrives work best with 3.42-3.73 rear gears. IMHO. You don't want the engine to lug when it is in OD.

What about a 200 4R with 3.73s?
200 4R Transmissions are a direct replacement. You will not need to shorten your driveshaft. I would recommend a Bowtie Overdrives Crossmember.

As far as a 700R4/4L60....The 700R4/4L60 transmission will work perfectly fine with 3.08 rear gears and a 350 engine with 290 ponies. Your car is a first gen, and FWIW the standard limited slip differential was the "G80" rear end on the 3rd gen IROC-Z Camaro's which included even the IROC's with the 5.7L aka 350 engines under the hood....The G80 was a limited slip/posi 2.77 rear end. And that was with the 1989 models with the N10 dual exhaust option pushing out 240 ponies respectively. The 1990 models had 245 ponies with a 350 and you may even see 2.73 or 3.08 gears back there as well if the more agressive 3.27 or 3.45 rear end gear was not ordered.

The GM engineers designed the 700R4/4L60 with a 3.06 first gear. The goal of the GM engineers was to get underpowered cars to launch harder with the very agressive first gear of the 700R4,and still deliver great gas mileage with a 2.77 or even a 2:73 rear end. In comparison a turbo 400 has a 2.48 first gear.

IMHO with a 3.08 gear in the back I would not put an overdrive in it. A 200-4R is a good choice because of the better gear spacing on the 1 - 2 shift as opposed to the bigger RPM drop on a 700R4/4L60 and their electronically controlled brothers the 4L60E and 4L65E.....

I hope this info helps. I love third gens and much of the theory of their technology can be applied to a first gen. Good Luck, Be safe & Happy Motoring! :thumbsup: :thumbsup:

Ive really enjoyed my 700r with my 3.08 posi. Around town I keep the shifter in 3rd so it doesnt slip into O.D. but on the highway I slip it into O.D. and the rpm drop is fantastic. I cruise at 60mph at about 1800 rpm. I love it and its performed great. The 1st gear is wicked low and the upshift into 2nd will still chirp the tires, even with 3.08's. I see nothing wrong at all with doing what you are planning. The highway mileage should be around 26mph if you dont have your foot buried into your Qjet. :)
fyi... my 350 LM1 was factory rated at 255hp but its been bored .30 over, a mild cam and forged pistons and balanced by previous owner, Im guessing around 270hp now.

Thanks guys, some good reading! John