I went to the 87 parts car and removed the window and regulator mechanism. This unit was pretty tight at the "X" on the lift mechanism.

I removed the window and drilled out the four rivets holding the mechanism on the 6/91 car. Once it was removed it was obvious that the pivot point at the "X" on this mechanism was a lot sloppier than I had thought. Evidently you can't really evaluate them until the arms are detached.

The mechanisms are different, and the 6/91 mechanism is held in place by four rivets while the bolted mechanism in the 87 car is secured with three bolts.

Two of the correct sized holes in the inner door were not eliminated when they changed to the four rivet setup. One of the holes for the rivets was in the correct position but too small for the bolt on the 87 mechanism. After drilling out the one rivet hole the 87 mechanism bolted up in the correct position. The electrical connector for the motor on the 6/91 car needed to be cut off and spliced onto the motor on the 87 mechanism.

The window closes as it should with the replacement mechanism but it is obvious that as it tightens up with the window in the full up position it wants to kick the top back edge of the window away from the channel. I will try to train myself not to force the window to the "far up" position in hopes that the mechanism does not wear at the "X".

According to Tasca's online catalog the electrical lift mechanism is no longer available, although it would appear that the manual mechanism is still available. Has anyone ever seen a manual lift window in a 740/940 in the US?

Thanks for everyone's responses.

Randy