The Stovebolt Site Forums The Parking Lot Big Bolts 1969 C50 dump truck - 2spd rear end won't shift

I just got me a brand new to me 1969 C50 dump truck. One problem with it is that the 2 speed rear end don't shift. How would I go about looking into this problem as I am new to this kind of truck. Where could I get the specs on the truck like: Motor(its a V-8), Weight, and Capacity(Dump Bed is 8'). Thanks for your help in advance.

P.S. Anything else that you think I sould know would be awesome. I've read so much in a short peroid of time I am more confused now than anything but I'm going to make it.

Drew

There should be a data tag on your door jamb. I don't have parts books for anything that new, but I would suspect it to be a 327 or 350. Is the 2 speed vacuum or electric shift. This needs to be determined before you start trouble shooting.

Assuming that you have an electric shift motor(1969 I'm sure should be) this link should help you to understand how the shifter works. You can do some basic trouble shooting to see if is is a power supply problem, switch problem, or motor problem.

http://www2.dana.com/pdf/AXSM-0029.PDF

Tad

Thanks for the info!!! This is going to be my project this weekend.

It doesnt match either one of those listed in the manual. Could it be vacuum controlled?

I have a '67 c50 with a vaccum shifted 2 speed axle. The 'switch' on the shifter is attached to a cable that goes down to a vacuum switch under the floor. My truck had sat for years and it was stuck. I pulled the cable and lubed it and put it back together and it works. I don't know any thing else about it but if yours is the same setup I would check the vacuum lines from the source at the engine back through the switch and to the axle itself.

Good luck and let us know how it works out.
-Richard

Do you have wires running to the rear axle or do you have a tube for vacuum? The vacuum will also have a round diaphragm on it that the tube connects to.

Tad

It has two tubes and a about a 4" diaphram that the tubes connect to.

How can I tell if its stuck in low range? Its wound tight with no load going down the highway at about 40 mph.

That pretty much says that it is.

Does anyone have a manual for woking on the Vacuum two speed rear end?

Jetmate,

The system is pretty simple.

There is a switch (valve) at the end of the push/pull cable below the floor mounted up high on the side of the transmission.

The Valve has 4 ports, 3 big and 1 small.

The big port facing the front of the truck is your vacuum supply that comes from the engine/vacuum tank.

The 2 big ports facing the rear are High and Low and run back to the actuator on the rear. When the cable is pushed down the low tube will have vacuum and when it's pulled up the high will have vacuum.

The small port facing the front of the truck goes to the back of the speedometer and is what changes the speedometer cable speed to keep the speedometer accurate in both rear speeds.

NOTE, MAKE SURE YOU CHOCK THE TRUCK BEFORE YOU START PLAYING WITH THE 2-SPEED, IF YOU GET THE REAR STUCK BETWEEN GEARS IT WILL FREE ROLL...

I bet your valve is stuck/corroded. To test disconnect both tubes at the rear actuator with the engine running and find the one that has vacuum. Now connect that tube to the other port on the actuator and you should hear/feel the actuator move the shift lever into the opposite gear. If that works your actuator diaphram is good.

Now have someone shift the push/pull cable and see if the vacuum switches to the other tube. If no change, your valve is stuck and needs to be removed and taken apart to see if it is fixable. Most that I have found are corroded beyond repair.

Let us know what you find...

Mike B

The Valve is corroded beyond repair. Where can I get one?

If you don't plan to use the truck for heavy hauling, I would route the hose with vacuum to the high side and leave it. The low gear in the trans will handle most tasks without needing the low range in the rear as well.