C4 or 200-4R tranny swap for L6.

[240Z Turbo]

I am looking serious into my next project which is an american auto trans swap into the early Z. I have narrowed it down to either the 200-4R as in the Buick GN or a C4. Both have advantages over the other. I plan to fab an adapter plate to mate the 200-4r to the Z and in the case of the C4 I will machine the 3N71B or 4N71B bell housing to bolt up to the C4 tranny. My specific question is this. On the 3N71B or 4N71B detachable bell housing, what is the diameter of the hole in the center that goes about the pump and what is the bolt pattern of the pump. Both can be approximates with a ruler and no exact measurement is necessary. Your help is greatly appreciated.

[Guest JAMIE T]

James, What has fueled your decisions on your transmission choices? It looks like you've chosen two totally differant style transmissions. C4, 3spd, no OD. And, 200R4, 4spd OD. I'd like to possibly do a similar swap on my turbo car, depending on how things go with it.

 

The C4 has it's strong points. Mostly it is VERY compact. I had a PA(Performance Automatics) C4 in my mustang at one point. Reverse manual valvebody and 'brake. It held up fine to 500+ hp/TQ. Expect to pay close to $500 for a QUALITY transbrake equiped valvebody. The older TCI 'brakes were made by PA and are very high quality. The later TCI version is not as reliable.

 

My personal opinion would lean toward the GM transmission. After the adapter is made, any popular GM trans could be put in there. I'd simply like to be able to put a TH350, or 'glide in mine. The powerglide will greatly soften your launch(1.76 first gear), allowing you to leave with more power and not break parts. The TH350 is more of an apples to apples comparison with the C4, except parts are cheaper and easier to come by for it.

 

I don't have much experiance with the 200R4. I do know that back in my early mustang racing days, guys would swap there AOD out for one. Now, Lentech has designed a BULLET PROOF AOD. I've driven a car so equiped. The 'brake was awesome, very consistant. Since then, I've seen the Lentach AOD's behind 800hp big block chevy's.

 

If OD is what you're after, then the 200R4 will fit your car well. If no OD is ok, then I'd still go with a GM trans. Being able to swap them around would be nice. Even though I made good arguements for the Ford stuff, I would still go GM just becuase of availabilty and cost.

[240Z Turbo]

I think you hit on most of the points. The reason for the swap is the Jatco is not the best for racing with 500+hp. I recently ran 2 11.1 passes and 2nd gear crapped on me. I pulled the tranny to find I bent the tab on the 2nd gear band and it had alot of heat wear(fadded black). I stuck in the new Kevlar lined band so it should hold for a while longer. I also want the transbrake and the ability to lock the converter which this tranny does not have. I have the non-electronic unit so it only locks the converter in OD. The 200-4R is a smaller unit than the Jatco, but most closely resembles it in gearing and that it has OD. Parts are fairly cheap and it can be built to survive the hp without breaking the bank. The C4 is so much smaller than any other Auto I have seen and the parts are much cheaper than the 200-4r and it will hold the power with no problem. However, the mounting approach is much different than doing the buick/olds. I like the idea of the adapter so folks can run the 200-4R, Turbo 350, powerglide, etc. However, I should consider what I need over what I think others will want. My tranny is our right now and I will pick up the 200-4R shell from my buddy and mock it in the car for clearance issues. After that, I will need to make a decision as to which tranny I want to run.