Alright, making progress. Pulled the dog house cover for easy of access (will also be out of the way for the duel fuel line mod). I drained the air tanks after running the truck for awhile. There was quite a bit of water! I’m not sure they had been drained in awhile. Good news first, the forward transmission breather is no longer venting continuously! When I unplugged the poppet vent hole, the pressure now vents through it when in neutral and forward gears. When I select reverse, it stops venting. When going from reverse to neutral/first, the vent continues to vent air until I select reverse again. As you may imagineX this causes the trucks low air pressure buzzer to come on after a few minutes. A bump of the throttle causes it to go back off and then gradually it will come back on.
Diagnosis:
Air leak: The poppet valves, maybe just the forward selector, is sticking, may have bad o-rings.
Fuel surge: I am almost certain at this point that I am drawing air.
Treatment:
Air: I ran some seafoam deep creep through the airlines to see if I can free up the valves. It says on the cab that it can be used for air tools so I figured let’s give it a shot. I also plan to drain the transfer case, run diesel in it while empty and drain until it looks good. I plan on replacing any questionable air lines while I’m there. If it does not straighten up, I’ll plan on doing both valves with a new o-ring kit I found on the introvertednet.
Fuel: I am bypassing the tank selector valve. I plan to run a transfer pump from the passenger tank to the drivers tank and only running the truck from the drivers tank. I believe a small 24v in-line fuel pump will be adequate. I plan on running all new fuel lines from the tanks forward of the selector valve. I also plan to replace any plastic lines I find that are questionable. While I’m doing this, I then plan to do the fuel fuel line mod.
Truck will be getting all new filters, oil change and some cosmetic work since it has a minor rust issue.
Contingency plan: if the air issues for the transfer case are not solved with the poppet valve rebuild, I will most likely source a t1138 and install it in place of the t138. I have a spare t138 but I think I would be happier with the lower rpm since I’m running stock 11.00x20. I do plan to upgrade to 11r24.5’s eventually. I will only use the truck off the interstate and local, mostly using it as a big farm truck. I might eventually use it to pull an rv but again just to the local lake. Any farther, I would want to get a more modern rig.
I am sure I don’t have to explain this to y’all, but I mess with these trucks mainly because my dad was in transportation in the army from 1978-1981 I believe. He still drives a truck and loves seeing them still. It would be cool if someone served during that time frame. He was 2/7 Calvary when he got out. Served a lot of his time in Wurzburg, Germany.
Will update as I progress
