Crossmember Info from Malibu Racing's site. >
Transmission Swap Tech
TH400 or 2004R
At first, I thought this was an easy swap. I read an article that said you can get the crossmember from any g-body equipped with a 2004R and it will bolt right up to the TH400. Well, that is partially true. IF you have a 84 OR LATER G-body, it will work. But, the 78-83 G-bodies never came with the 2004R. The frame rail crossmember mounts are different from the latter year models. The latter year G-bodies frame mount locations that extend further back (toward the rear of the car). Since the 78-83 models do not have these, you will not be able to use the factory crossmember (unless you make the frame extension piece). Other options are to either get a crossmember from G-Force Performance, get a "universal" crossmember, modify/fabricate your own, or make a frame extension piece and use the stock TH350 crossmember. I modified mine by removing the mount pad from the front side of the crossmember, then using 1/4" thick steel plate, welding it to the back side of the crossmember. I then drilled an elongated hole for the transmission mount bolt to go through. Not too difficult to do yourself if you have access to a welder. Otherwise, you will need to get someone to do this. The TH350 driveshaft will either need to be shortened, or you can use a stock one from a later model G-body that had a 2004R transmission. Remember, you will have to use the yoke from the TH400 on the new driveshaft.
