I am wanting to put a overdrive transmission in the Cutlass. As I’m running a 3.91rear end gear,and talk to my tranny man! I originally was leaning towards a 200R4 and he said the parts for those are really getting hard to come by! He is leaning me towards a 700R4 which is smaller than the 400 I have in the car now as far as tunnel issues. Does the adapter plate from Summit actually work well? And do I have to do a custom built torque converter to adapt to the thickness of the adapter plate? I read the reviews on Summit customers and they said they had to have 5/16” of washers between flexplate and converter to make up that difference for the adapter plate! Just curious what everyone else has done! I don’t want to rig with a fix that may break! Any replies are greatly appreciated!

 

I have a 700R4 behind a 455 in my 67CS. I used the Transdapt plate kit. It is about 5/16" thick so you need to use long alignment dowels for the transmission. The hub on the torque convertor uses an extension to plug into the crank and each convertor bolt has 2 thick washers between convertor and flexplate. Stock convertor bolts will be too short and they are metric.

I've had no problems during the 3 years mine's been in place.

 

Parts for the 200-4R are readily available from CK Performance and many other sources. Your trans guy just doesn't want to build one.

 

Look into Gear Vendors. https://www.gearvendors.com

 

Agreed. I rebuilt mine last year using the aftermarket, there is no shortage at all of OEM style or upgraded parts for the 200-4R.

 

http://www.ckperformance.com/List/GM...missions/2004R

 

Lonnie at extreme automatics has parts and transmissions. Dave Husek at turbo Buick as well. Find another builder

 

I personally would not put a pile of garbage 700R4 behind anything with power. Driveshaft might needs cut along with an adapter plate. I used the cheap thin adapter plate when I put and Olds 350 in my 94 Z71, could only get in 4 of the 6 bolts. As long as you have a good adapter like this US made one, that part won't cause you issues. https://www.summitracing.com/int/par...0061/overview/
As long as you have a good 2004R core to build, the rest of parts are out there. Both transmissions need a lot of upgrades to live, the 4L80E and Gear Vendors are also options.

 

Just to add to this, the 700R4 is a different overall length than either the TH350 or TH400. The crossmember location is also different from the other two. Driveshaft definitely needs to be changed, and new holes will need to be drilled for the crossmember. The 200-4R is the same overall length as a TH350 and uses the same driveshaft. The crossmember goes in the TH400 location. It's a much simpler swap. Both the 200-4R and the 700R4 need internal mods to live behind a 455, so cost to build either is about the same. Few shops deal with the 200-4R any more, so they tend to push the solution they are more comfortable with, whether it is the right one for you or not.

 

And just to add one more item to the pile.....with that 3.91 rear end ratio you have the 700R4 is NOT the best choice for your combo. It has a steeper 1st gear (3.00 to 1) than the 200 (2.75 to 1) which you just don't need behind a 455 which are not torque challenged like the SBC's the 700 was meant for at the factory. The 1 - 2 spread in the 200 being smaller means less of a jump between gears which equates to better performance - if that's what your into

 

I really appreciate all of the replies! And I am going to talk to another vendor/builder and explore other options towards still going with the 200!