1978 Cat 931 (D3) left track won't steer. help!

I has a similiar issue with a D3. Does your tractor have the pedals coming up through the floor or hanging down below the dash?

Regarding the dipsticks. One is the transmission and one should be the bevel gear oil.

There are valves that release the steering clutches on a D3. There are valves that have a little piston that gets pushed whe you push on the steering clutch pedal. They ride on the assembly. You can see them if you remove the floor plates. The valve may need a rebuild kit. They are pretty simple

Cat had a change over on the oil. Call the dealer and ask them what the book says to use.

Is it pedal steer? Will it release and turn if the rpms are up and you stab the left or right brake pedal?

coming up through the floor

[quote="chugwater crawlers"]Regarding the dipsticks. One is the transmission and one should be the bevel gear oil.

There are valves that release the steering clutches on a D3. There are valves that have a little piston that gets pushed whe you push on the steering clutch pedal. They ride on the assembly. You can see them if you remove the floor plates. The valve may need a rebuild kit. They are pretty simple

Cat had a change over on the oil. Call the dealer and ask them what the book says to use.

Is it pedal steer? Will it release and turn if the rpms are up and you stab the left or right brake pedal?[/quote]
i see the little pistons behind the steering pedals. Is there anyway I can test that the valve is in fact bad?

You can make sure the stem moves into the valve when the pedal is depressed. The first part of pedal travel starts too disengage the clutch. Continuing pushing the pedal then applies the brake for that side.

You can test the valves by a 600 psi pressure gauge to the steering clutch plug/port on the side of the tractor.
The book says check the oil viscosity and the capacity first. They used to use 10W oil, but I recall they upgraded to something else. Next they recommend checking the steering control valves, followed by checking and cleaning the transmission filter screen. If the screen has a bunch of black bits in it you. probably need a clutch.

They stick after sitting so it just may be stuck.

If you have a small hill you can drive up it and push the pedals and see if it rolls back with the pedals about halfway depressed. That my indicate the brakes need adjustment.

One of mine would stick when it was cold and work free after pushing dirt for awhile.

I would invest in service manual. It's worth it. Check Ebay.

Most likely your problem is a collapsed bearing on the front of the steering clutch release valve.
This valve is a Pressure Reducing valve, it lets trans pump pressure(400PSI) in and shuts it off when
it compresses the spring up front. If you want to release the clutch you step on the peddal and push on the bearing of the valve. This compresses the spring up front and more oil pressure is allowed through the valve and the clutch is releases(at about 200+PSI). A worn bearing will reduce pressure you can build and result in your problem.
Later Bob

I took the steering control valve out and inspected everything.

The valve looked good and was a little cruddy, but cleaned it all up, put it back on and no change in the problem.

What would be the next thing/area to check?

Did you do the pressure check as advised in previous post?