Hello, I was a heavy duty truck mechanic until last august when I was laid off and have been working for myself since. I went out to look at a dumptruck a man had and there was also a 951c he wanted me to look at. I don't have much experience with these and had a few questions about my diagnosis. The problem is that the unit will not turn left. When you push the steering pedal down it feels like it tries to grab but it's not grabbing enough. You can see the rear sprocket that the track rides on wobbling and jumping, and this shakes the whole unit. If you mess with the idle speed and the pedal and the gearshift you can sometimes get the left steering to grab, but only for a second. I understand that these units use what is called a "steering clutch" to make turns and that it is behind the sprocket that gets shaken around. Do these symptoms match up with a bad steering clutch, or one that needs to be adjusted? I have tried to find some information online, but haven't had much luck since this unit is older. What all is involved with replacing the steering clutch? I assume you would have to take off the track and the sprocket, and then the clutches are behind there. Any help is appreciated, I would like to replace the parts if I am able to; I just don't want to get myself into a job that is way too big for me. I am cummins certified, ase certified, etc, and have extensive experience with drivetrain work in tractor trrailers.
If you can actually see the left track sprocket "jumping around", we got big problem. You've either got a problem with the sprocket shaft, or worse, final drive destroyed. Neither is an easy repair on that machine. If I'm not mistaken, on the 951C you have to remove the track frame to disassemble finals. Steering clutches are in the rear case under the operators seat and fuel tank. They can be removed without taking the tracks or final drives off, but from what you describe, you have way bigger problems than steering clutches.
I was hoping you wouldn't say that :Banghead How is the sprocket driven? Is there a shaft that could be sheared off back there and that is why it seems like it is trying to grab? Can I pull the sprocket shaft like a normal truck axle shaft? I.e. pull bolts from hubcap and smack with hammer to pop out? What other diagnosis can I do on this thing? I'd like to do the work, but have no problem telling him to take it to the cat dealer if necessary. The sprocket was wobbling like an old open face wheel does if it isn't squared up correctly.
Wow, it's been so long since I've worked on one of these that the details are vague. You have the final drive case, which is the large case bolted directly to the sides of the machine at the rear. That's where the "final" reduction gears are. At the bottom of the final case is where the output shaft comes out, it goes through the sprocket, and the end of the shaft fits into a support bearing on the outside of the track frame. The support bearing is under that square looking cover plate with 4 bolts in it at the rear of the track frame. It could be that the sprocket has ripped loose from the shaft splines which, if that be the case, would require at the very least shaft and sprocket replacement. I'm near certain, in order to remove the sprocket or the shaft, you have to remove the track frame, someone correct me if I'm wrong. I can't remember if you have to remove the final case to replace output shaft. I think you could see a lot better if you remove that shield that covers the rear sprocket and get a better look at what's going on in there.
I tried to remove that shield the other day but only had a small tool kit with me since I was just writing estimates and I needed a 15/16 wrench for one bolt and only had up to 7/8 in the truck of course. I'll see if I can't run out there again and look at it a little more closely.
I hear ya, and those bolts have a habit of getting STUCK! There is one other possiblity for the wobble; someone has fitted a "weld on sprocket ring" and didn't fit it proper. Removing that shield allows you to view things a whole lot better. Another thing you could do is remove the drain plug in the bottom of the final drive case on each side of the tractor. Pull the plug away just enough to let some oil into a small container, and see if any metal comes out. If a man wants to sell a machine, he should have no gripe with a potential buyer checking things like this. If he does, he's not being an honest seller. Also, what kind of shape is the undercarriage, that would be, the track chains, pin bushings, front iders, top and bottom rollers, and sprockets. To check your bottom rollers, start machine, lower loader arms all the way down, then roll the bucket forward to lift machine front off of the ground. Then the bottom of the track will sag down and you can reach in an turn the bottom rollers. A good roller should be snug to turn, but no so tight you can't turn one, that one would be siezed. Likewise, you shouldn't be able to simply spin one. Just don't stick you hand way in there, just grab the outer flange of the roller and be ready to move your hand if something happens, wouldn't want to loose some fingers here. BTW, Where's my manners! Welcome to the forum. :usa
Welcome crossthreaded.Will the 951 turn to the right ok?Is the wobbling spocket on the left side of the tractor? Any poping or grinding noise?
Oil analysis if you have the time would be helpful as well....
the unit turns right fine, there is a popping/grinding noise when trying to turn left though. The wobbling sprocket is on the left side as well. I can't tell you which one (popping or grinding) for sure as I don't remember, but it was definately making some noise. I can try to take a video of it tomorrow, but I am very busy with summer classes right now so I am not sure when I can get back out there. I was going to pull the plugs to check fluid levels but also only had a 3/8 drive ratchet with me. I was very unprepared as I was only there to give an estimate for some exhaust manifold gaskets and electrical system work on a POS F600. He might not want me to do any work on the dozer after he sees my estimate for the dump truck
Usually when you say the sprocket is wobbly, you also say, open up your check book. A good quick first check as previously mentioned is to remove the final drive drain plug, and see what kind of shavings are on it. You may see some extremely fine mushy particles on the magnet and that is ok. Slivers, chunks, gear teeth and rollers out of bearings point to a bad failure. Also take a rock bar and wedge it between the sprocket and final drive cover and see what kind of play you have. Those bearings run with a pre-load, so the should be none. Seperation of the track, removal of the roller frame is necessary to work on the final drive. Plan ahead and prepare to remove the steering clutch in case you have to replace the spur pinion, before starting your teardown. The sprocket is pressed on the hub, but most of the time with a bad failure, it has already loosened itself. The final drive can be removed cover and all if need be, then you can take it somewhere and have it pressed off. Good luck.:usa
hmm... so what are we talking if he takes it to the cat dealer 5k, 10k, more? This sounds like more than I would be willing to mess with out in the field. I'm not going to tie myself up for a week with something I won't be able to fix. Just want to get the guy prepared for what cat might tell him. btw, thanks for all the help so far
That's a repair I wouldn't want to do in the field.
Final Drives, Firstly its worth checking the brake adjustment, do the adjuster bolts up firm then undo 1 1/2 turns, this might liven up things some what??? if the f/drive has failed its not a bad job to tackle on site, sadly I do them as a regular thing and to me its better to do them where they stand than do more damage moving them about, the track and frame has to come off letting you get into the sprocket etc, the sprocket will need pulling off so will the outer support bearing, for this you need a bit of kit, if you were in the U.K. I would do it for you no problem, there may be someone local you could ask to help you with this task, its not a bad job to tackle, and it could be a good learning curve for you , best of luck. tctractors