I really need some transmission help!

[CamaroAdam73]

Ok so i just bought an 1988 monte calro SS (matching vin and title numbers!) and the old transmission was blown (thm 200 4R), the new transmission is a 700 R4 and here's where the problems start...

I'm not sure if the old transmission was a THM 200 4R or a 200 R4, are those actually two different transmissions?

And now down to the real problem, The torque converter for the 200 4R doesn't lockup to the 700 4R, it slides on to the input shaft but it won't go on all the way because i THINK the diameter of the input shaft splines are bigger on the 700 R4 than on the 200 4R, are they supposed to?? i know the guy we bought the 700 R4 off of said he built the 700 R4 for racing, but never specified what he did to it. And the guy at advanced auto said the Torque converter from the 200 should lockup to the 700.

The bigger spline on the input shaft's have the same number of teeth (27), but on the 200 4R they look different, the 700 R4 has the same number of teeth on the bigger spline on the input shaft, but the teeth also look different from the 200's.

Can somebody shed some light on this for me?? i'm at a dead end on what to do

[silicon212]

You cannot use the 2004R converter on a post-1984 700R4 transmission, due to the spline difference. You will need a torque converter for the 700R4.

There was never a 'TH200R4', just a 4R.

Note there is a difference in driveshaft lengths on the two transmissions (the 700R4 requires a driveshaft about an inch shorter).

Prior to about the half point of the 1984 model year, both transmissions used a 27-ct spline input. In the half 1984 year, the spline count on the 700R4 went up to 30. If the trans you have uses a 27-ct spline input, then the TC you have should fit. Double check it. You also need to align the oil pump lugs up with the slots in the TC in order for the converter to fully fit within the bell housing.