Case 850 slowing down

[ledgerd123]

I have a case 850 dozer, when your driving straight at full RPM it does fine and sporadically it starts to slow down, also whenever you make a turn it slows down. the RPMs don't come down just the speed. im currently looking for a hyd schematic if anyone can help

 

[guisep3]

When was the last time you changed the hydraulic and transmission filters? Any error codes?

 

[ledgerd123]

no error codes, theres only been 74 hours on the filters (changed in june)

 

[ksm_82]

It slows almost to a complete stop going left. It's sometimes slow going straight forward. If it is steered slightly right it will pick up speed, but if turned left at all it will slow almost to a stop to turn.

 

[ledgerd123]

KSM is the technician working on the machine

 

[guisep3]

Sounds like you will need to have the pumps pressure tested. My first step would be to do an oil analysis of each of the final drives. There should be a filler plug you can take off to take the oil sample. If you have that done, it will help you determine if there is metals and dirt in the final drives. Also you may need to hire a mechanic that has the gauges and fittings to test the main pump etc...no disrespect ksm. I have a new holland d85 LT which is essentially the same machine. A gentleman on here named GaryHoff helped me and another guy that has your exact machine diagnose our problems. I believe he was a case mechanic. He would know what psi you should have on all the test ports.
Again his handle was GaryHoff.

I would definitely pull oil samples to see what you got going on with all the major components.

 

[alrman]

There could be clutch pack problems or convertor issues .....

Does the transmission pressure gauge still work on this machine?
What pressure readings do you have when cold & when warm?
At operating temp - at an idle - click through each individual gear range. Each selection should take the same amount of time & the pressure should be the same as in neutral. Lower pressure indicates oil leakage.

When steering the machine are the levers being used or the brake pedals?

 

[brianbulldozer]

I am thinking it might be helpful if the OP shared what series machine this is (850, B,C,D,E,G,H,K,L,M). When I read error codes I think everyone is talking about the later hydro static machines, when I read steering levers and brakes I think everyone is talking about the older 2 speed steering machines.

 

[alrman]

Very true brianbulldozer,
I assumed an early straight 850, however I missed the 3rd comment re the machine having "no error codes" - so it could very well be a K L or M

 

[ledgerd123]

it is a K model

 

[looneytunes]

Check and make sure ur relay and fuses are good and making contact. Also check the wires going to the selenoids on side of the transmission. The insulation on the wires is bad about cracking and coming off and when water or mud gets on em it's makes the machine do crazy ****. I had that happen on my 05 850k.

 

[guisep3]

So just in case anyone is in need, I have a back up computer for a case/ new holland dozer. They call it the travel controller in the manual I believe. It's retails for over $8000.00. Make offers if anyone with a case dozer needs a computer. I had one go bad and bought a back up.

 

[GaryHoff]

Seems there is a lack of information here.


So steering left slows down both tracks?
Does it react this way in all speed % ?
Does it act this way in forwards and reverse?
Does it act better cold vs when the machine is hot?
Is this a new issue, or has it gotten worse over time?
Does the machine miss track? (in any speeds)

 

[ksm_82]

Seems there is a lack of information here.


So steering left slows down both tracks?
Does it react this way in all speed % ?
Does it act this way in forwards and reverse?
Does it act better cold vs when the machine is hot?
Is this a new issue, or has it gotten worse over time?
Does the machine miss track? (in any speeds)

I apologize, I got my left and right mixed up. Steering Right slows the entire vehicle. Steering left speeds up. It acts that way in both forward and reverse. For some reason, my left track will not get up to speed. It seems like the computer is compensating when going straight, slowing the right track to go straight via speed sensors. It does the same thing weather hot or cold. I'm not sure if this has happened to this machine before or if it was the first time it has happened, or if the problem has gotten worse over time. I wanted to pull the spool valves to see if they were stuck or if there was a bad o-ring inside, but cannot pull the spool without pulling the entire tandem pump. Also according to Case, the pumps are not serviceable, which seems hard to believe.

 

[GaryHoff]

The pumps are serviceable. They are just Rexroth pumps, so most hydraulic shops can easily repair them. Not sure what spools your wanting to remove from the pump.

Need a bit more information still:

The left track is slow in all speeds, and in both directions?

1. Is the right track fast in all % speeds? The computer can only compensate so much to make you track straight. Is there any % speed that it tracks straight?
The reason I ask this, is because the travel motors piston gets stuck sometimes, so you will have one motor stuck in high range. This will make you miss track until you reach the same high range speed in the other motor. You will also have low power in one side.

2. The other issue may be a leaking cross over relief. If that is the issue, you will likely have a slow track on one side. It will be slow and low power, in all speeds. It will usually be more noticeable in one direction, usually forwards. The cross over reliefs tend to fail more on machines that are worked very hard or have higher hours.

 

[ksm_82]

#2 seems to be what it is doing. It is much more noticeable in forward than reverse. The machine doesn't have too many hours and I'm not sure how hard it has been worked, but it does sit for long periods of time between uses. The machine doesn't seem to mistrack at any speed, but when going straight it seems to take a while to get up to speed. Even at top speed, when turning right, the machine practically stops. Turning left the machine will noticeably speed up.

 

[GaryHoff]

A quick check is just to switch the cross over reliefs. (item 16 is on top, and the one you will switch it with is just below) Just make sure you really clean the area good first before removing any parts.

 

[ksm_82]

Thank you for your help. The relief valves are not the issue. I'm guessing the next step would be to check the travel motor pistons. I'm not sure exactly how to do that. Any help would be appreciated. Thank you.

 

[GaryHoff]

If the track motors are stuck in high gear, the machine will misstrack in some gear. I would pull off the coils on the drive motors, and see if it misstracks. Does your machine have a winch? Sometimes the motor coil wires rub on the winch drive shaft.