Two trucks 79 and 88 both had regular trans, I’m planning to install the overdrive 518 in both and wondering if the trans mount can adapt to the overdrive?
With some fabrication you can make it work. IIRC, I made an "adapter" steel plate to attach the three bolt pattern OD to the two bolt pattern non OD pattern in 1991. Couldn't find a newer truck in the JY at the time. Not too much trouble. Driveline angle is the hard part. For that I had to cut, fabricate reinforcements and lower the center portion of the crossmember. Find an OD crossmember and save a lot of trouble.
A bolt in thing?
IIRC, we welded it to the existing mount, thinking we had bolt clearance issues. I remember we smoked the rubber mount, might want to start with a poly mount? The "adapter" plate matched the 3 bolt pattern of the OD trans. We should have added an offset bend, there's also an elevation change between the 2 bolts and single bolt. We used washers to make up the difference, not the best but it worked.
edit: oh the crossmember? Yeah, I think so. I finally sourced one but never got around to installing it before I sold the truck. There's a LOT of different part numbers, I think they're all interchangeable. You may have to drill new holes in the frame, the OD is 6 15/16" longer than the non OD. We used the welding on of the adapter plate to make up the difference.
