Been working on putting a 1999 D5C LGP with pedal steering into service on our forestry operation and have run into a snag with the steering. I'll try and explain so that maybe someone with experience can give me some direction. When we got it the right pedal was ( adjusted it up yesterday after waiting a week to get the service manual so we'd do it right ) soft and the unit just did not want to go right. Adjusted it up, backed the unit out of the barn ( only the 3rd time it has been moved and in the other two instances it was only to get it off the transport and under the barn......only a few yards )and immediately noted that the unit would still not go right properly. Though the two pedals are now equal in operation the left one will allow a "feathering" of the turn whereas the right will not. In fact.......and this is hard to explain......when the right side is pushed nothing happens until you get it well on down with a good bit of pressure and then the whole unit will come to a complete stop at which point it will then turn right. It's as if it is a "all or nothing" situation with the right side. In reading the service manual ( and mind you I am NOT all that mechanical ) it seems that the valve that is actuated by the pedal has a initial function that serves to "feather" the unit and then, once a certain point is reached a full break function kicks in. If this is correct then my uneducated guess would be that the valve is where the issue is. Have not ruled out something else but as the unit has all of 1500 hours on it and taking the fact of the right side needing adjustment it seems a good guess that the valve has been bad for a while and that the Florida Forest Service ( Previous owner ) had either not noticed as the operator worked around it or as it was a old unit that they had scheduled for replacement they just chose not to mess with is. So does this sound like a reasonable diagnosis of the place to attack first? Or am I missing a piece of information and some understanding of what is happening? Help appreciated.
I ran into something similar to this on a D3C a few years ago. It had a broken spring in a valve, exactly where I can't remember, to many other repairs since then! What happened was that the clutch didn't release because of low oil pressure and the brake had to force it to slip to make it turn. You will need a pressure gauge for some diagnosis.
Nige and the other Gurus will need a serial number or at least a prefix
6ZL00974.........I think.
Good thinking D5C III TRACK-TYPE TRACTOR Machine Serial Number - 6ZL00974 (Build Date - 23/06/1998) Checking if I can find something
Thank you........been out burning the woods today, using the tractor......which is not broke!
The steering valve is a solid starting place. If you have the ability to do it check the steering clutch pressures. The port location should be on the outside of the frame in a recess, just above the track. Pressure should be around 300-320 psi. If you aren't getting this pressure then check the steering valve to see if there is a bearing failure or a spring issue. If you are developing 300 psi then you will have problems deeper in the machine, possibly a sealing ring blown out in the clutch. The last sentence is only speculation, start with getting you pressures and then you can move forward with a plan.
Thank you. But do tell/show me with what I take that pressure reading? And I am assuming that the reading is taken with the pedal pushed in sufficiently to engage BOTH the clutch and brake functions of the unit? Obviously with the unit in neutral......?
Let me begin by saying that if you aren't familiar with working on bulldozers then you should call in reinforcements. You will come out much cheaper and much safer in the long run. Watch someone work on it and learn something before you start throwing dollars and fingers at your dozer. First, pressures are taken by removing the plug from the port and installing a pressure tap. You then use a pressure gauge to measure the pressure. Pressure gauge example, will look similar to this but not exactly: Pressure is measured with oils at operating temps, parking brake set, high idle. Pressure should be 320 psi or higher. If you don't have this pressure then your clutches can not release, most probable solution is to replace the valve. There is service literature indicating a known problem with the steering valves in this serial number range (valve replacement is recommended by Cat.) If you do have the recommended pressure then you can check mechanical linkage, namely the cam bearing that actuates the clutch lever. Make sure it is intact and that there is no slop in the movement. From there you would have to go into the steering clutches, most likely a blown ring and/or used up clutches. Best of luck.
Thank you..... Have done as you suggested......professional on the way. I will watch closely.......and try not to impede his work!