The Stovebolt Site Forums The Parking Lot Big Bolts c/50 Dump

Hello, This is my first post and I was wondering if someone could help me out. I am thinking of buying a 71 c/50 dump truck but the seal around the pto shaft on the pump leaks. It leaks enough that the bed does not lift. The seller told me he thinks he let the bed down too fast and blew the seal and he thinks its an easy fix. What do you guys think? Will it be very pricy/hard to fix or could the problem be something bigger? This issue is a make or break on the sale for me and I would like to get back to him soon so the truck doesnt get sold. Any help would be greatly appericated, Thanks -Spencer

Hy spencerRbRown, the seal on the pump input shaft should not have to retain high pressure, but you may find a groove worn into the shaft once you remove the seal, this groove will have to be repaired or the new seal will not survive for long if at all. A "Speedi-Sleeve" for a shaft of that size can be installed to provide a new wear surface for the shaft seal. The seal can be pryed out or pulled out by drilling a hole through the seal and installing a sheet metal screw to use as something to pull the seal out of its bore. The hoist may work but may be too low on fluid for the pump to raise it, hope that helps.

Is the pump and the PTO all in one or does it have a drive shaft? Is the PTO leaking or the pump? If its the PTO leaking, it has nothing to do with lifting. If its the pump, it may be an easy fix with a speedi-sleeve or it may not be fixable at all. I have hydraulic pumps on 3 of my trucks to pull end dumps. I have never had much luck repairing hydraulic pumps. I would prepare for the worst...about a $600 pump.

Thanks for the help. The pump has a shaft, and it is leaking where the pto shaft goes into the pump. I think I can see the light blue seal sticking partway out? The guy with the truck said he never added fluid to it untill the day it blew, perhaps he over filled it? I also thought it would be strange that the seal would have pressure on it. I am thinking the problem is indeed that the fluid leaks out too fast as this truck has no tank only the fluid in the hoist piston and pump? If someone can send me a pm and let me know how to post a pic I have one of the unit.

What he probably did was to fill it with the bed partially raised. This allowed him to overfill it. Then, when he let the bed down, the extra fluid had nowhere to go, and so it took the path of least resistance, and blew out the seal.

The proper way is to leave out the plug the first time you lower the bed. That way, any surplus fluid can escape. Then raise the bed and replace the plug.

Also, make sure the bed is SECURELY blocked up anytime you are working under it. A more desirable alternative is to get at it from underneath if possible, but that's not always possible.

Rich, I think that may be what happend it looks like the seal around the shaft is pushed partway out. Thanks for the help.

What you have described is an underbody hoist with a piston cylinder where oil is displaced from the top end of the cylinder and pumped into the bottom. Upon lowering it the oil flow simply reverses. There is no pressure on the gear shaft unless there is slippage past the gears which indicates the bronze faced wear plates are worn. Otherwise (and if your lucky) you might have rotational wear on the seal itself and that is easily replaced. So you could have a minor problem or perhaps a more serious problem if the pump needs to be rebuilt or worse replaced. The thing that makes it expensive is that the valve was cast into the pump body on most brands so your looking at a pump and valve assembly, not just a less costly pump only replacement. See if you can determine the brand of the hoist, that will help with repair parts which are becoming harder to find these days.

any idea on what the worst case is? a new pump? at what cost?

Thanks for all your help everybody. I got the truck home and took off the pump. The seals around the imput shaft had been pushed out. I used a flat punch and hammer to re-install them. I put it all back together and filled it back up with oil. It works great! 0 $ and an hour and a half later and she dumps again, best part is 3 days later there isnt a drop of oil under that pump!

Glad you got her going again. And the price was definitely right!