The Stovebolt Site Forums The Parking Lot Big Bolts keeping a 1955 dump truck happy

I just bought a 1955 dump truck and had a few questions for you before I put it to work. It runs OK, the previous owner delivered it from 30mi away. He just replaced the rotor, plugs and adjusted the valves - the rotor and plugs are clearly new, the valves I have to take his word on.

Mainly I was wondering about fluids. What should I change or check?

The dump is a little hesistant and doesn't extend fully, I am hopeing it is just low on fluid. There doesn't seem to be a reservoir, but there is a fill plug on the cylinder. Do I need to do anything special or just open it up and top it off?

The previous owner said he had to top off the brake fluid every couple months. Is this something I should track down or not worry about for a while?

How about the rest: rear differential, transmission, etc?

My plan is to use it on our property and for short trips to the sand and gravel pit ~3mi <35mph, but I would like to take decent care of it and I am not familiar with trucks of this size/vintage - closest was a 65 suburban I used to have. Thanks!!!

O' yea, the numbers stamped on the frame are 2550004068. I pluged this into the VIN decoder and it didn't come up with anything other than the year and factory. The plate on the door frame says GVW 18000lbs and 125hp. Is there any other way to figure out the model? Thanks...

ccogg
Sure would like to see some pictures of your new truck. As you will see I am in to the dumps.
You have come to the right place for info and a genuine good time. I must warn you though it's a little like potato chips you can't eat just one.

You fill the cylinder at that plug. If you can get to it fill it with the bed down. If not brace the bed ( for your safety ) fill it and leave the plug out and slowly let the bed down with something under the truck to catch any that may get pushed back out. Put the bed up and replace the plug, only after bracing the bed again. Please never get under the bed without a good brace in place.
Yes find out where the brake fluid is going and fix it.
Check all fluids as you would in any vehicle
Above all be safe and have fun with it, and welcome to the Bolt.

Dittos to everything said above. If you have to raise the bed, by all means brace the hell out of it before you go under there!!
The reason for leaving the plug out the first time you let it down is,in case you overfill it. If the plug is in, you'll blow out the seals when you let it down.
If it's at all possible to work from below, without raising the bed, that's a better option, at least from a safety standpoint.
On mine, I just went to the farm store and got their basic hydraulic fluid.

Oh I forgot the oil type I like to use AW-46 Hydraulic oil
And I am sure Rich will not be the only one to come by and hammer the point of not going under a raised box without properly bracing it.

Check your gear box & rear end! Seems the brake fluid & gearboxes always get overlooked. The oil in my '56 looked like someone added about 3lbs of chocolate to the box & called it good. More sludge than liquid, thankfully still had lubricating qualities tho.
I still need to drain & service the ram on my beast as well since it only goes about halfway up and leaks alot, leaving that for later tho. Same thing as yours, no resivior, just a fitting on the top of the ram.

never hurts check/ change it all

Ccogg,
You came to the right door. Did the same thing. Bought a little dump to work on my project house. Next thing you know, I'm doing restoration on the truck! The good thing about these old iron horses is that they are simple. Every box contains a lubricant that can benefit from being changed. Start with the basics of replacing brakes to make it safe at any speed. Stopping is more important than going fast. Never seen a lift that didn't have a resevoir. That's a new one for me. Many years ago I serviced hydraulic lift gates and so the basic concept of either electric or power take off activated pump is familiar to me. Common sense would lead one to search for the way the hydraulic ram is activated and where the fluid is stored. That same thought process would lead one to the unavoidable fact that hydraulic systems have the capability of simple failure to one or more components. When that happens to a lift gate, it usually stays on the ground and a pool of fluid follows. What goes up must come down and if a dump bed decided to come down on its own perhaps thru the work of a terrorist or aliens, it would ruin your whole day if you were under it.
Last but not least, you absulutely must post pictures of the truck in question. It's a rule. The punishment for breaking that rule is one thousand lashes with a wet shoestring. You wouldn't want the shoelace squad to show up at your house in sunny Oregon now would ya?

The old underbody hoists are simple closed loop systems. The pump pulls oil from the top of the cylinder and pumps it into the bottom to extend the shaft. When the piston gets to the top it bypasses into the pickup or suction side of the pump. There should be an air vent built into the fill plug. If yours doesn't have one just use a pipe plug and drill a 1/8" hole thru it and put a cotter pin in the hole to offer some protection from dirt entering.

Dave:
Dum question: does that limit the travel of the hydraulic ram? Mine will keep going to full extension failure and there's no way to prevent that other than being very careful.

"Mine will keep going to full extension failure"

What makes you say that? Makes no sense to me.

Dave please correct me if I am wrong. Orchidskip by using the non working end of the cylinder for the reservoir it can't over extend. The non working end or in the case of these dumps the rod end of the ram, has a smaller displacement than the working end do to the space taken up by the rod. So the system will run out of fluid before it can overextend.

With a resevoir system like I have, the pump has an endless supply of fluid and unless there's a way to trip the valve the ram can be overextended. Lift gates have a mechanical device that literally moves the valve to the closed position once the lift has reached the bed. This is possible because of the proximity of the mechanism to the valve. My valve is mounted on the firewall, far away from the bed so no way that I can think of to engineer a trip device to shut off the valve when the ram reaches a certain point.
I guess I'm just thinking out loud. The old system you're describing sans resevoir, keeps the fluid in the ram in a finite amount so the fluid simply runs out before the ram can over-extend. Genius.

Heavy: The way you describe it the pump would cavitate and start to pump air. It works because the upper end is connected directly back to the suction side of the pump as I first said. A simple bypass system. So it really doesn't run out of oil it simply circulates and yes that is a bit of genius. Works the same with or w/o a reservoir. IF is is newer and has a relief valve built into the directional valve then it goes directly back to the tank. The only old underbodies I've seen with reservoirs were units built to have a multi-function hydraulic system and used a bank valve to operate various other functions like a plow truck, etc. and cooling became an issue. They just weren't needed. I'm curious as to what type of control is on that firewall mounted valve and what type of valve it is.

Also the liftgates of today utilize DC pumps and electric controls in 98% of applications. They use a relief valve and have no mechanical linkage but I am familiar with the old ones too as orchidskip describes. Almost never see one anymore or even a new gate with a PTO pump. I haven't sold one in 10+ years. All this stuff has evolved of course but it has not necessarily improved. In 50 years you won't see any electric pumps still running I'd wager.