Overdrive trans change over

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.

crossmember

adapter plate

mount

This worked for my NV4500 swap. I didn't need the adapter plate as the mount bolted directly to the trans.

That is a work of art.

Thanks, great ideas so far

look at mopar parts giant. it appears that there are 2 different setups. i just went thru this when i shortened an 86 long bed frame to a short bed frame. i thought that i had all the right stuff but things did not work out correctly. i went to two different pick/pull yards and found 3 trucks to pull the stuff off of. 2 were different. i still try to collect the stuff as i have a bunch of trucks. look at the p/p's.

Thanks, I’ll try to use the mounts off both vans somehow. 92 and 94

I swapped my '71 Sweptline and my wife's '79 LRE from 727 to 518. Built adapters for both that bolted to the factory crossmember...not pretty but they've both done over 20,000 miles with no issues. If you've got the mount to go with the 518 and average fab skills it's not a big deal. You CAN do the "work of art" mount if you've got the skills and equipment. With the pressure and vacuum switch setup for shifting the OD and lockup, it's an awesome swap and well worth doing.

Last one I did was a two-wheel drive D100. Crossmember out of a 92 Ramcharger was used. set it in the frame drilled six holes and everything was bolt in. And note to self when using a plasma cutter for piercing the holes in the cab is on the frame. Make sure you stick some heavy steel between the two otherwise you'll have a hole in the floorboard. Ask me how I know🤣