I am replacing the crossmember on my 88 GXL because it completely ripped in half straight down the middle. The engine is still in the car amazingly. I'm wondering if I can do this with the motor in the car and the car on ramps. The control arms are connected to the subframe, will the wheels give and the car drop on me? How should I go about swapping in a new subframe with the engine and trans already in?

 

I did this on jackstands. You have to disconnect the steering rack and control arms. There are numerous nuts that you have to get to as well to drop the crossmember, as well. It's a pretty easy job, just make sure to hold the motor up with a hoist unles you plan to remove it. And try to keep the rack supported as much as possible so you don't break the rubber on the tie-rod ends. Mine were pretty old and a little grease is now leaking (may have been before). I don't think I'm forgetting anything.

 

Jack stands under the "frame" rails in front of the subframe you can use a jackstand under the trans as close to the engine as possible and use a block of wood (2X4) on top of the stand (to protect the trans) this will hold the engine in place well.

I am not responsible for car falling on you. This is the best way short of using an engine hoist to hold the engine up, which would be optimal.