Servicing hyd on 71 Chevy dump truck

AlanB · Mar 22, 2009

My current internet connection is poor (wildblue) and cannot usually upload pictures.

I have bought a 71 Chevrolet C60 dump truck with a Galion / Hercules dump bed.

It has a Pto box off the xmsn, driving a driveshaft back to the pump, and a seperate control knob to engage the pump.

Everything on this truck leaks, and I need to service the cylinder.

There is no resovoir to service, the lines from the pump go direct to the large lift cylinder.

I believe I feel an access port (I am guessing 1/2" pipe) on the top highest point of the cylinder, which would be the highest point on the system.

I am thinking I need to fill that port to the top in the collapsed state and that would be the correct fill level. Unfortunately I cannot acces that plug from the bottom.

Current thought is to cut an access door in the bed of the dump and fill from there, but I am certain there is a better way of doing it as this thing must have been serviced many times in it's life.

I also thought about taking the hoe, lifting the bed halfway, and servicing it half full and trying that.

Anyone familiar enough with this type system from my probably inadequate description to lend me some guidance before I do something stupid?

Thanks

Diamondpilot · Mar 22, 2009

What ever you do secure the bed with cribbing if lifting it half way and servicing.

Have you thought about a pump? I have one that goes on the top of a 5 gallon pale and I use it to pump out 80W90 gear oil into diffs and things like that. It has a 6' hose and I have adapted it down to about 3/8" outside dia to fit small plug holes.

Really cant help you much. I do maintain a Ford F-700 dump truck for a neighbor in exchange for using it but never had to service the hydro system. Not even sure what brand it is. All I care is that it works.

Chris.

mattman · Mar 22, 2009

Thats a very important thing the cribbing that is. I have not seen a dump bed that did not have a hydraulic fluid tank somewhere's on the truck. It takes a good bit of fluid to fill the cylinder at full lift. I have not seen a cylinder with a built in tank for the extra fluid needed. I guess there could be a way without a tank, but I would trace the hoses going into and out of the pump to look for a tank.

Someone will chime in with more knowledge than I have.

kennyd · Mar 22, 2009

mattman said:
Thats a very important thing the cribbing that is. I have not seen a dump bed that did not have a hydraulic fluid tank somewhere's on the truck. It takes a good bit of fluid to fill the cylinder at full lift. I have not seen a cylinder with a built in tank for the extra fluid needed. I guess there could be a way without a tank, but I would trace the hoses going into and out of the pump to look for a tank.

Someone will chime in with more knowledge than I have.

I agree, sounds very strange to me also. I bet the "fitting" at the top of the cylinder is a vent, not a fill port.

Wis Bang · Mar 22, 2009

mattman said:
Thats a very important thing the cribbing that is. I have not seen a dump bed that did not have a hydraulic fluid tank somewhere's on the truck. It takes a good bit of fluid to fill the cylinder at full lift. I have not seen a cylinder with a built in tank for the extra fluid needed. I guess there could be a way without a tank, but I would trace the hoses going into and out of the pump to look for a tank.

Someone will chime in with more knowledge than I have.

Small, single stage, dump cylinders don't have a tank, at least the one we had & the ones dad's workplace had didn't. The cylinder housing is oversize to act as the reserve. Follow the hoses, there should only be two going to and from the PTO mounted pump. You add the fluid where OP indicated.

Multi-stage units like those on a ten wheeler +/or a dump trailer need alot more fluid.

A track jack or porto-power will raise an MT body and WILL be a dangerous place so use a few 4x4's to support the raised body. Opening the plug on the cylinder jacket will vent the system so there will be zero resistence to even slow down the falling dump body...you can't have enough support.

Stimw · Mar 22, 2009

IIRC some used the cylinder to lift the bed and used the back side of the cylinder for the reservoir. In which case you can fill it in the up position. Is there a hose coming off the top side of the cylinder? Does it go to the input on the pump?
As stated ALWAYS block the bed when in the up position. I met a guy once with only one leg. He said he climbed up on the frame of a dump truck to get to the rear end and the bed fell severing his leg! The worst part was the bed had been up all weekend and when he climbed up it was monday morning.

DANOCHEESE · Mar 22, 2009

like above make sure the box is cribbed. Lower it on the cribbing to make sure it will hold. Think of it like a leg hold trap and you are the prey. The box always wants to get the guy who makes it go up and down.

EddieWalker · Mar 22, 2009

Hey Alan,

Here's a picture of mine. Is it similar?

I have the PTO pump that powers the cylinder that lifts the bed. It is a single action cylinder that when engaged, lifts the bed. Then when the pressure is released, the bed comes down by gravity.

The cylinder area above the piston is your storage area for fluid. There is no need for it to be full, and if you make the same mistake that I did and fill it up, the bed won't come all the way down. Basically, when the cylinder is pushing the bed up, the fluid comes from the other end of the piston, through the hose, into the pump and then pushes the piston up. When released, the fluid flows the opposite direction.

I add to mine with the bed up and blocked with 2x6's to keep it up. Then the screws comes off with a philips head screwdriver. I use a plastic, disposable cup, and pour in one cup full at a time. When I get it right, the bed will raise all the way. I then add two more cups and call it a day.

Do you have the same triangle shaped brackets? Be sure to grease them real good. I've broke the ends off of mine twice. The first time, I had a local guy weld it back together and it was a simple job. The second time, it twisted the heck out of the metal and I had to take it to a machine shop to weld it up and align it. That was $500 and two days of pain to get it apart and back together. MISERABLE PAIN!!!!

Eddie

AlanB · Mar 24, 2009

Thanks guys,

Yes, it is very much like your's Eddie, but I have never seen it up so I am not positive on the triangles but I must have something similar.

Spoke with an old timer master mechanic yesterday and he went through the servicing, he suggested lifting it with a forklift (of course I had the forklift at the house yesterday, on my way to his shop where I was dropping it off

)

He said that you get it about halfway up, then get it pumping, and then keep adding fluid till it will go up to full travel, then close it up. That as it leaks you will see the bed will not go all the way up and that is the time to service it. He also suggested cribbing for safety.

Call me a weenie, but I think I am just going to cut a floor in the bed and make a little slide in / bolt in plate to go in there with a beveled edge. Then I can pull the plate and service it from above. I have a feeling as leaky as this thing is, servicing it will be a fairly regular occupation and being between the frame and doing it, with or without cribbing just makes me uncomfortable.

If my plate hangs a bunch of stuff I can always weld a flush plate back in and service it the "normal" way.

EddieWalker · Mar 24, 2009

Alan,

I like the plate idea, but once you get fluid in there, that's a done deal. You'll find the leaks quickly enough since there is only one hose. But over the long term, you will have to grease those pins. mine has four pins per side, plus the main pivot rod that holds all the weight of the dump bed. You will have to figure out a way to get under the lifted bed and grease those fittings.

I tried to lift my bed with my loader, but didn't have much luck. I didn't have the forks for it then, so you might be able to do it with the forklift where I wasn't able to with just a bucket. When I broke mine, I lifted it with a bottle jack and allot of blocks of wood. Back and forth, with bracing in three places on both sides. It's slow, tedious and painful, but it works.

I found that the rings on my piston were very much like a piston on a car. They were also all lined up so that fluid could flow right through the ends of the rings. I kept the same rings in there, bu turned them so that the ends were staggered. Now my bed stays up when I'm not using it. It will bleed down over night, but it's way too slow to see. Before, you could see it coming down and had to keep pumping fluid into it to keep it up with a load.

Good Luck,
Eddie

Wis Bang · Mar 24, 2009

It wouldn't be the first small dump body w/ a hole in the floor!

You should be able to get seals & hoses to stop the leaks and fix it right. What will you do when the hose or pump seal pops while lifting a load? Even if you could get to the offending part, you would need to shovel the stuff out enough to reach the hole which will be close to the center of the bed & therefore under the most of the load...b/4 you could add oil.

I've seen flat steel supports, one end bolted to the body floor supports & pinned at the other. Pull the pins & raising the body makes the free end swing out become a support once it is vertical & you let the weight down some so the bed is supported. Add a few 4x4 props for insurance & go to work...

I'd fix the leaks; pump seals & hoses are easy to replace & any good hydraulic shop should be able to find/make parts if the cylinder is leaking...Like Eddie said it could be as simple as the rings not being staggered...

Anything you do to it will add to it's eventual re-sale. Even if the chassis is shot; the dump body will have value.

AlanB · Mar 26, 2009

Funny you said that Wis bang as that was the discussion, I bought a dump bed for $900, just happened to come attached to a 71 Chevy Chassis

Might look at it this weekend again, have to see what SWMBO has in mind, probably servicing mowers.

Dirthog · Mar 26, 2009

you can cut all the holes you want in the bed but you still have to fill it with the bed up and they will use some oil they are a single acting cyl there will be some seepege past the packing and then it blows out the breather ran one of those for years. Take a piece of 2" steel pipe and make a prop for the bed it does not take much to hold it up. first time you have something stuck in the back of the bed you will see how hard it is to get it to lower you will then reliese all the more it takes to keep it up. The mack I have only has a 1-1/2 pipe on each side from the factory.

EddieWalker · Mar 26, 2009

When I grease or work on mine, I put a 2x6 on each corner to keep it in the upright position. I just wedge it between the dirt, behind the cab and into one of the cross beams on the bottom of the bed. Simple, cheap and effective.

Eddie

sandman2234 · Mar 26, 2009

I drove a International with a hydraulic lift fifth wheel on it, that was set up like your dump. No tank, just the cylinder for a reservoir. We filled it from the top side of the cylinder, with the cylinder retracted. I think I still have one of those pumps out in the garage. Cutting a hole in the bed is easy enough, as long as you double check the location so you don't have to cut it twice. Doing it with the bed up and blocked is easy enough, but tends to overfill the cylinder/system.
David from jax

Dirthog · Mar 27, 2009

The old chevy dad had you had to fill it with the bed up! It would not raise the whole way and you knew it was time to add oil never leaked a lot but if you would run it steady all day you might have to add a quart or so to make it raise clean up most of the time we never ran it to hall more that a couple of loads a day so it was no big deal.

AlanB · Mar 29, 2009

Dirthog, why would I have to fill it with the bed up? (After I had a hole that is.)

Thanks

Diamondpilot · Mar 29, 2009

Told the guy who has the Ford Dump Truck about this discussion yesterday and he also said you had to fill it with the bed up. He said he has used a chain high in a tree then pull the truck forward to lift it before.

I am guessing the reason for the bed being up is the position of the piston in the cylinder with it down. You can not get enough fluid in the cylinder. He also said his truck and bed have a pocket to place a 4x4 to prop the bed up.

Chris

Dirthog · Mar 30, 2009

because when the bed is down you can not fill it to the proper level in fact if you take the plug out with the bed down you will lose oil and the bed will not raise!

Wis Bang · Mar 30, 2009

Filling the cylinder when the piston is collapsed [body down] should give enough oil to get the body up. The housing holds all of the oil not in the plumbing/pump when the bed is down and the pump simply transfers this to push the piston out. If you overfill this resivour w/ the body raised, where will the excess oil go when you lower the body? This is a single action system [power up only] so the piston has to drain back into the housing to let the body down. Too much oil will prevent the piston from retracting into the cylinder unless there is enough weight to blow out a leaking hose/pump seal.

Fix it properly and don't fill the housing...