TH350 to 200R4 Swap

[joe_padavano]

I don't think you can just slide the crossmember back on a G- like you could on an A-Body. Though the 200-4R and 350 are the same length the mounting pads are in two different spots. Some folks modify the 350 crossmember by cutting the pad off and welding it to the opposite side. I've only seen this done on the aftermarket cross-members like G-Force so not sure if it'll work on a stock member.

This is not a good idea in any case. Structurally, the trans mounting point should fall on a line drawn between the two end mounting points of the crossmember. Look at the factory crossmember and you'll see this. If the trans mounting point is offset from this line, is imposes a twisting load on the crossmember and thus on the lower flange of the frame rail. I'm sure there are lots of anecdotal examples of people making this work, but the issue is long term fatique, not short term load failure. Bottom line is: get the right crossmember. 200-4R crossmembers are a dime a dozen for G-body cars.

 

[86cutlassrules]

Joe I cant argue with you the problem is i cant find a gbody in the junkyards by me, yes I am as shocked as you are. Up until I bought mine there was a new one in there every week.

 

[DrRansom442]

Buy an aftermarket like G-force .... the RIGHT crossmember will be cheaper then screwing up your transmission or frame or any other damages that may occur by improper mounting. I know when I was looking, I had problems finding a 200-4r crossmember and the th350 crossmembers seemed to be EVERYWHERE - funny cuz I will swear most of the G-bodies I've been around had the overdrives ... think when I bought my 81 it was the first 3 speed Cutlass I encounterred.

As for the OEM 200-4r crossmember it is not straight accrossed .... mine bolted on the passanger side in the same holes the th350 did ... driver's side (because mines a 81 and not designed for the 200-4r) require an extention piece for the frame. The th350 is straight acrossed the 200-4r is angled.