Hello, I have a 1986 Kenworth Tandem dump truck. It has a 13 speed Eaton Transmission and a 2 speed Axle. The 2 speed axle switch is on the dash and has a high and Low. I can’t seem to get the axle shifted out of low. My Truck only goes about 55 mph tops. When I flip the switch to high, it doesn’t make any difference. Is it possible that I’m not shifting it to high correctly? I climbed under the truck today and had my wife flip the switch… I can hear it add air to the rear end and release air when shifted back to low. Not sure what the problem could be. Any help is appreciated.
+ Maybe best to take off the air and air dia/fram 0ff just to see if it has a hole in it and if the arm leading into rear end is still able to move from low to hi by hand or pry tool?
I’m going to work on this tomorrow. I’ll take off the valve and inspect. I’ll report back what I find. Thank you!
I took off the air diaphragm. Gear rod pulls in an out. Cleaned it all up and put it back together. Still won’t shift to high range. Not sure what else to do. The dump truck still goes almost 60.
Is it a twin screw? I have never seen a pre 90's truck with twin screw and 2 Spd. Several single axles but not a screw.
I know you said the rod moved but were you actually able to manually shift it between ranges and verify that?
Make sure that the rubber is put in the right way if its in backwards it will not move enough to move the arm to switch gears, ck for cracks it it carefully?
Sorry it took me a little while to post an update. I raised my dump bed and started tracing air lines. Turns out that the diaphragm I cleaned is for the locking diff. I traced the air line for the 2 speed axle switch and sure enough it’s capped off. I don’t see anywhere that this 2 speed switch would plug into the diff. Wondering if someone replaced the rears at some point and eliminated the 2 speed. It’s just odd that my truck only goes about 60mph tops. It’s a Kenworth W900 tandem dump truck with a 3406b and Eaton 13 speed. I’ve only owned this truck a couple of months and don’t know any prior history on it.
Need to know tire size and rpm at 60 to make any sensible guess as to what is going on. A 13 direct with 4.30 gears on some form of short rubber comes to mind?
