Just bought a dump truck

[EddieWalker]

Just read about your problem and want to agree with Builder's advice. Sometimes you have to get the rear tires off the ground, but ususally you can tell with the vehicle in neutral. Just try to turn the drive shaft by hand and see if it moves. It shouldn't. Usually what happens is the cap over the roller bearings in the U joint breaks and then the U joint flops around. Then it's just a matter of time until the rest of the U joint breaks off and you are stranded.

If it's not the U joint, get the rear end off the ground and spin the tires by hand. If you can hear any noise coming out of the rear end/differential, you know it's in there. I've never had any work done on my dump truck axle, or anything that large. I have had work done on half ton axles. The labor was minimal since I brought the parts to the shop. For them, it was just a few hours or work, which saved me allot of money.

If it's the rear end, find a shop that works on them first and ask what you can do to save money on the repair. Pulling the axle off is simple enough and a good way to save money.

Do you have a two speed rear end? I don't know enough about them to know what to look for, but have heard that they do go out and they can be pricey to repair/replace. If the driveshaft and differential check out fine, that is the only thing left to check.

One last thought. My rear leaf spring broke yesterday while hauling dirt. I herd a snap sound while pulling out with the load. I drove it to the area that I'm dumping it and dumped the load. Then I got out and looked it over with the bed up. It took me a minute to see that my axle was crooked. Then I saw the broken leaf spring. I doubt this is what happened, but wanted to suggest to you to just look at everthing with the hope that it might be something totally differnt then what you think it is. Of course, 9 times out of 10, it's the thing you don't want it to be.

Eddie

 

[bearmtnmartin]

I just bought a 1974 GMC 6000 with a flatbed dump on it. It has a 350, with a 4+2 rear end. When I first went to check it out it started up easily and ran real well. I drove it home about 55 miles, man that sucked. It seemed like it was in low the whole time. I realize its a huge truck, but it didnt want to go faster than 45 mph. I pulled over once and to check it and the headers were glowing red, so I let it cool down and checked the water everything was ok. Not sure why they were glowing. To me it seems like something isnt right, even when your going 45mph that is with your engine wrapped out. Is there a way the rear end is stuck in low and its not switching back to high maybe?

It may be that you don't have enough jam to get up to highway speed. The headers were red because it was working so hard. As has been mentioned in this thread, most of those brucks came with big blocks, bit it was very common for that to be ripped out when it needed work and replaced with a dime a dozen small block from a pickup or some such. But the small blocks have a shorter stroke, so they don't generate enough torque. That might not show up so much at lower speeds and lower gears, but on the highway you are way past the torque curve when you try to wind it out in a higher gear. Or maybe you have the right engine and the rear end is geared really low. Or the timing needs some adjustment.

 

[Builder]

If the tach was on the red line, then you might have been driving in low range on the 2 speed rear button.

If the truck was not redlined at 45, then you have either a weak engine or a gearing issue. A GMC 6000 is a small-medium duty truck, probably ~9,000-10,000 lbs empty, so a big block gasser should easily do the trick.

One easy way to tell "what you got under the hood" is to put it on a truck dyno and see how many RWHP you have.

 

[chickenhead]

Wow just discovered the real truck in the gmc 6000 I bought. Turns out the 350 is a nice powerhouse for this truck. I finally had time to get under the hood today and found that the distributor was as loose as could be. I got it timed right and torqued the bolt back down and took it for a spin on the highway, and man what a different truck. It climbed even the steepest hills with no problem, and went 55mph and was barely hitting 3500rmp.

 

[Builder]

Wow just discovered the real truck in the gmc 6000 I bought. Turns out the 350 is a nice powerhouse for this truck. I finally had time to get under the hood today and found that the distributor was as loose as could be. I got it timed right and torqued the bolt back down and took it for a spin on the highway, and man what a different truck. It climbed even the steepest hills with no problem, and went 55mph and was barely hitting 3500rmp.

That's great!

I had no idea you had a 350 in there....I thought it was a 366 big block.

The 350 was probably the best small block engine ever built.

Glad to hear it was a cheap fix, too.

 

[GT2]

That's hopefully what you did. That way the repair is inexpensive.
Lay on your back under the truck with some gloves on grasp the driveshaft by the u joint and see if you can shake it. See if it moves or makes a rattle. Visually check the ujoint to see if it's damaged. If it is, it's a 10 min replacement job.

If it's not, it could be damage to the ring & pinion in the rear.

Just read about your problem and want to agree with Builder's advice. Sometimes you have to get the rear tires off the ground, but ususally you can tell with the vehicle in neutral. Just try to turn the drive shaft by hand and see if it moves. It shouldn't. Usually what happens is the cap over the roller bearings in the U joint breaks and then the U joint flops around. Then it's just a matter of time until the rest of the U joint breaks off and you are stranded.

If it's not the U joint, get the rear end off the ground and spin the tires by hand. If you can hear any noise coming out of the rear end/differential, you know it's in there. I've never had any work done on my dump truck axle, or anything that large. I have had work done on half ton axles. The labor was minimal since I brought the parts to the shop. For them, it was just a few hours or work, which saved me allot of money.

If it's the rear end, find a shop that works on them first and ask what you can do to save money on the repair. Pulling the axle off is simple enough and a good way to save money.

Do you have a two speed rear end? I don't know enough about them to know what to look for, but have heard that they do go out and they can be pricey to repair/replace. If the driveshaft and differential check out fine, that is the only thing left to check.

One last thought. My rear leaf spring broke yesterday while hauling dirt. I herd a snap sound while pulling out with the load. I drove it to the area that I'm dumping it and dumped the load. Then I got out and looked it over with the bed up. It took me a minute to see that my axle was crooked. Then I saw the broken leaf spring. I doubt this is what happened, but wanted to suggest to you to just look at everthing with the hope that it might be something totally differnt then what you think it is. Of course, 9 times out of 10, it's the thing you don't want it to be.

Eddie

Thanks for the suggestions guys,
I got out to my property this week end and crawled under the truck, Surpise!! One of the rubber "doughnuts" around the center drive line support had some how worked its way out, and the drive line was dancing around in the bracket.
Removed the two bolts re-inserted the rubber and presto! new truck!
I hauled 16 tons of #3 base and one rental track skid steer this week end and had no problems, well I thought I had a problem, turns out a rock was sitting on the edge on the hyd tank and scraping on the drive line. The noise was "howling" up the drive line and made me think something was sawing itself apart under there!
Eddie, I had some worries about leaf springs this week end myself. On one gravel run the guy loaded me with 6.3 ton of rock! Thats about 2 ton too much I thought? But the truck took it fine, however I wont do that again, I'll go back to the pile and dump some out!
Sorry I dident get many pics, I only had 2 days to level and build a pad for my trailer. Notice my home made roller? It worked pretty good, but needs vibration. I'll have to work on that.

 

[GT2]

That's great!

I had no idea you had a 350 in there....I thought it was a 366 big block.

The 350 was probably the best small block engine ever built.

Glad to hear it was a cheap fix, too.

Glad to hear you got it going!
My 350 feels pretty strong also, considering what it lugging around!
I have no problem getting to 60 mph, but its getting a bit spent at that speed.

 

[EddieWalker]

Eddie, I had some worries about leaf springs this week end myself. On one gravel run the guy loaded me with 6.3 ton of rock! Thats about 2 ton too much I thought? But the truck took it fine, however I wont do that again, I'll go back to the pile and dump some out!

When I bought mine, I knew it was a five yard bed and with side boards, it could haul six yards. One of the first things I did was to add a pair of PT 2x10's to the top of the bed so I could haul that extra yard of dirt. With 6 yards of dirt, I had one problem after another. Things would just snap on me. I've rebuild the lift mechanism twice, blew out the hydraulic cylinder and the list goes on and on.

After the second rebuild of the lift cylinder, I decided to cut down the odds that I would have to do that again. Each time, it was a several week process to get it fixed, and those were terrible days. I now limit myself to five yards per load. I grease before every day of using it and I always check my fluids. It's still breaking on me, but so far, it's mostly small stuff.

The more I use my dumptruck, the more I realize that I should have spent $300,000 for a new ADT dump truck. Of course, if I had that kind of money, I'd just hire it out and not have to deal with breaking dump trucks ever again.

Nice job on the rock. I love buying rock and hope to get some more down this year.

Eddie

 

[Builder]

Thanks for the suggestions guys,
I got out to my property this week end and crawled under the truck, Surpise!! One of the rubber "doughnuts" around the center drive line support had some how worked its way out, and the drive line was dancing around in the bracket.
Removed the two bolts re-inserted the rubber and presto! new truck!
I hauled 16 tons of #3 base and one rental track skid steer this week end and had no problems, well I thought I had a problem, turns out a rock was sitting on the edge on the hyd tank and scraping on the drive line. The noise was "howling" up the drive line and made me think something was sawing itself apart under there!
Eddie, I had some worries about leaf springs this week end myself. On one gravel run the guy loaded me with 6.3 ton of rock! Thats about 2 ton too much I thought? But the truck took it fine, however I wont do that again, I'll go back to the pile and dump some out!
Sorry I dident get many pics, I only had 2 days to level and build a pad for my trailer. Notice my home made roller? It worked pretty good, but needs vibration. I'll have to work on that.

Hey, you're a pro dump trucker/ excavator already!!!

Lookin good.

There's a lot of older dumps out there that are just "given-up" on. Their owner just doesn't want to investigate the little problems and fix them. Many trucks can be bought cheap and with a small reinvestment, be brought back into a usefull work or weeked tool.

Look what you've got and how little it cost you. That truck will haul more than an F-550 for 1/8th the cost. Might not do it in high style or off road without 4x4, but look what you saved $$$. tell you what would make your truck look great is a new paint job on the cab and a chrome front bumper. Probably get all that done for ~ $1,500 and that truck would look excellent. Maybe a nice GMC red or white color.