I recently installed a 355 in my 63 impala. I went a little over kill on the carb and i have a vacuum leak on the side of my intake manifold. So there is no way for me to know the correct horsepower. my estimate is about 430. right now i have a p/g and its leaking. Its probably the pump cause i just changed the front and rear seals. Long story short i want to know which tranny to throw behind my motor. Its going to be my weekend warrior / cruiser. Any advise would help. thanks

Overdrive is the only way to go. You have two choices. A 700R4 is the single most common OD tranny because GM made more of them for a longer time than any other (the 4L65e is still a 700R4 it is just electronically controlled). Your other choice is a 200R4. Why mention it, because the 700R4 requires shortening the drive shaft 3/4" where as the 200R4 just requires moving the transmission cross member back to the TH400 mounting point (it is the same size as the TH350 and the PowerGlide, and uses the same driveshaft). Both OD trannies will require a new torque converter and flex plate as they are metric instead of SAE.

Big Dave

Ditto to Big Dave. All I can add: You are getting high enough on horsepower that you need to be concerned with how these trans are rebuilt and what is being used inside. Bowtie Overdrives lays it all out.

Thanks for the info. What is the difference between the 700r4 and the 200r4. both are over drive and both are 4 speeds right? is it just the size and mounting? but which is better to use if im concerned about money when converting from a p/g?

That is about it. Were the transmision mounting point is and the overal length seperate the two. The 200R4 was the first OD tranny ever built by GM. It had a lot of loyal followers who think it is GM's gift to the world. The 700R4 had a steep learning curve to catch up, and lost a lot of converts due to early failures. GM has since beefed up all of the broken parts inside to were it is just as strong as the TH350 that it is based upon. If you needed a stronger tranny than the 700R4 (4L60) then you would go with a 4L80e tranny which is the TH400 made into an OD tranny.

Big Dave

I just took a gander at the bowtie overdrive website and i shouldnt need anything stronger than those. im still stuck on which one to use. even with the mounts for the 700 i'll still need to shorten the driveshaft. which leaves more room for error. but the 700 comes with more options for the converter. got kinda lost on the tv cable section though. im sure you can tell im a newbie to this. but im sure with a few books and a little hands on i'll be good. but in the mean time any advice would be GREATLY appreciated.

I installed a 2004R into my 70 Impala last summer. I've had zero problems and it was basically a direct bolt in for the Turbo 400. It is 1/2" shorter than a 400 (short tailshaft), and uses the smaller 350 yoke. The 2004R has no seperate rear housing, so the "case length" always appears longer than a Turbo400 when you're reading the specs. If you use the long style yoke, you don't need to shorten the driveshaft at all. The rear mount is 1/4" shorter than a Turbo 400 which is a moot point since most crossmembers have slotted holes for the mount bolts. I chose this trans, because the 700R4 has a weaker input shaft due to the 3 oil passages that are drilled into it. The 2004R has only one passage. Additionally, the 2004R has a 2.74 first gear ratio, as opposed to the 700R4's 3.06. Overdrive ratios are .67 for the 2004R and .7 for the 700R4. The hardest part about this trans swap is finding a Chevy pattern bellhousing 2004R. Most were produced with the Buick/Olds/Pontiac bell. It should be noted that this is the transmission used in Grand Nationals from the factory. My car is an original 454 convertible and has a 3:31 rear gear. I hope this info helps you or maybe someone else.

All 1986-90 Impala police cars shipped with the heavy duty version of the 200R4 transmission. It uses a Chevy bolt pattern instead of the BOP (though most 200R4 trannies made since 1987 used a universal bell housing that will bolt up to any GM engine). They are a direct bolt into any B-body going back to 1977.

Other cars equipped with the Chevy bolt patern bell housing are:
'81-82 Chevy Caprice, Impala Assorted V8s
'86-90 Chevy Caprice, Impala Chevy V8, Olds 307 V8
'81-90 Chevy Caprice Wagon 307 V8 only


Big Dave