OK, thanks. I'll pick a new MLPS this week and I'll let you know what that does.
It's a 302, my Haynes book is worthless in this area. I'll have to get out there and really look around for that wire. What's the best way to investigate it, just try to follow it from one end to the other looking for problems or is there some trick I can do with a multimeter?
The 4x4 lights do work, the 4x4 LOW RANGE light just comes on and off at random as I drive (like when I hit bumps and such).
Yes, when I do all the shifting it drives fine, it's only if I drive in D the problems occur.
Thanks again for all your help, I really appreciate it. I'll keep you posted whether that MLPS replacement works.
EDIT- quick question: is the MLPS the same thing as a neutral safety switch? I can't find the former on autozone's website, but the neutral safety switch looks very similar in the pictures. If so maybe it'll also fix the problem that makes my truck only start in Neutral not in Park.
I installed a new MLPS and though I could only drive it briefly, it seems to be shifting a LOT better. It no longer bounces back and forth between gears and it seems to be actually driveable without manual shifting.
A couple things:
It still seems to be shifting too early, or maybe the torque converter lock is engaging too early, it seems to kind of stumble on takeoff with this. Could this be caused by the bad low range switch on the transfer case? Or the vehicle speed sensor? (the speedometer reads correctly, could the VSS still be bad?)
Also I must've messed up the shifter cable as the needle on the stalk is no longer over the correct letter. I didn't see an obvious way of adjusting this. Any tips?
I just wanted to post a final followup just in case anyone else has this same problem.
Today I unhooked the low range switch on the transfer case to see if it helped the problem. Interestingly enough the LOW RANGE light would still come on and off even with the switch completely unhooked. I followed the wire from the switch and found that a whole bundle of wires had broken off its wire mount and was just resting on the front driveshaft! Every time I had it in 4x4, it would rub and the front driveshaft would burn off the coating. I followed the harness and found it was also the harness going to the transmission itself. There were 4 wires in it which were stripped and being constantly shorted against the front driveshaft and each other as I drove.
I unhooked it all, pulled it under the truck and with the help of black tape and wire ties I got it back into working order. Took it out for a spin and it drives like a new truck! Shifts perfectly every time, which it hasn't done in ages.