My grandson stopped by this afternoon, seems he has an issue with the trans in his 77 or so Dodge W150 727 4x4 trans. He says it has a good low, a good 2nd, but drive is like neutral, but he also has good reverse. Last week he changed out the carb with a GM style Edelbrock AFB. He doesn't have the Mopar carb adapter, so he has the throttle linkage cobbled up, as well as the trans kick down cobbled up. I asked him if the kick down was working, and he told me it was working great and it was shifting right as well. I have my suspensions about the kick down adjustment.

With this info, short of pulling it for a rebuild, is there anything we can try to do to get drive to function again? Gene

I bet if you take it for a test drive. It won’t shift correct. Place it in drive and give it 3/4 or so throttle. If it shifts into second right off, he smoked high gear because he did not have the correct throttle pressure adjustment. He would not be the first to do that. One turn of the adjustment makes a difference in the way it shiftm

It could be several issues for loosing pressure the the front clutch pack.
I would pull the valve body out and use compressed air to check for leakage to the front clutch drum.
If that checks out, separate the valve body and inspect the fluid circuit paths for cracks or breaks in the walls.
I had a crack in my valve body wall that had the same symptoms, but that was really unusual.

my thinking is likely pressure loss to the front drum?
ff the trans ran real hot, likely the lip seals in the drums need to be replaced

Well, my grandson and his buddy decided they could adjust the kick down adjustment and fix it. They messed with the linkage and left my driveway 3 different times. When they returned the last time, it wouldn't even back into the yard. I guess they "fixed it" good. Now he has to figure out his next move.
Thanks guys. Gene

Been there. Kids learn the hard way. Go buy a Edelbrock AVS 2 with the correct linkage adapter for the carb, so the kick down will work property, AFTER you get the trans rebuilt.

The kickdown is actually a pressure valve, if it wasn't going all the way back at full throttle he toasted the high gear clutches and burnt the steels. Yank the trans and after rebuild MAKE SURE he gets the kickdown correct or he'll repeat this problem.