1988 D-6H Differential steer.

[Multiracer]

Well maintained machine, has been in use on and off for weeks. last use was to clear a lot of mud and snow from our haul roads.
Today I get on, all fluids are good, starts fine, lift the brake handle, cycle the blade, place it in gear and hit foreword....... nothing.
It will turn left and right, with your hand on the trans filter you can feel it go into gear, you can feel it shift fore and reverse, but no movement.
Ideas from the masses of knowledge ?

 

[overworked]

Possible torque converter, is the drive shaft spinning in -- neutral? -- in gear?

 

[Multiracer]

I would have to remove the floor. I have not done anything to it yet.
If it steers each direction doesn't that mean it is making pressure or is it a different pump ?

 

[Bob/Ont]

It's the steering pump that makes it counter rotate and it works regardless of drive from the trans. Like OW says check the drive shaft for rotation when in gear. If the shaft is holding open the throttle and see what happens. If the shaft holds check the linkage to the park brake and the pedal linkage aswell. After that it's a trans pressure test. Trans priority valve sets up the brake release pressure and then it dumps into the trans valve(modulating relief) to set up P1 that is shared with Differential Pressure valve that reduces it by 55 PSI for P2. The Modulating relief valve dumps into the Ratio Valve that balances Torque Inlet oil pressure against P1 pressure to protect the torque from blowing up with cold oil going through it. Clutch modulation time is controlled by the Plastic Screened Orifice that controls the speed of oil getting behind the load piston.
Later Bob

 

[Multiracer]

Floor is out, driveshaft spins no matter what, no slow down no stop. It spins the same in gear or out.

 

[Bob/Ont]

First check linkages then check pressures in all gears, Priority, P1, P2 and converter inlet on back of trans. Check priority with brakes on and off.
Later Bob

 

[Multiracer]

The tech with the gauges will be over in the morning.
Thanks for the help.
Ron

 

[Multiracer]

Top of filter housing 400psi, P1 400psi, P2 no pressure. So sounds like converter is good, 123 shift spool is good, problem appears to be in the F/R spool.
Any other thoughts ? Monday or Tues. he will remove the valve.

 

[Bob/Ont]

Take the trans valve pack out and change the plastic screened orifice. If it's clogged up you will only get initial pressure in the trans. Kind of hard to explain from here but if you change the orifice it should work.
Later Bob

 

[Multiracer]

Is the trans valve pack the valve with the foreword reverse cable hooked to it ?

 

[Bob/Ont]

It is inside the trans case, Speed and Directional cables are hooked to it. Your problem may be as simple as not being able to shift into neutral for start up.
Later Bob

 

[Multiracer]

Update,
Priority valve seems fine, pressures are good in foreword 1,2, but 3 is no pressure. Same in reverse.
Sooooo, out comes the trans for a look see. the guys are guessing a stuck piston or a seal failure from clutch wear ?
My shop is rented right now so off to their shop it went today.

 

[watglen]

update?

 

[Multiracer]

It went to the shop last Thursday. I think the trans just got pulled today. I hope to have better info on Friday.

 

[Multiracer]

Well, The trans is out and on the shop floor. They will separate the components on Monday and start searching. They did find a handful of clutch in the bottom of the cavity.
I will update as I get updated.

 

[Multiracer]

Here is the verdict..... 3rd gear clutch discs and steel plates have worn below tolerance and allowed the hydraulic piston to travel out too far past its usable limit. This allows the seal to come apart and let the pressure bypass.
3rd gear is engaged in neutral as well as several other gear combos. Just because your machine does not run in third gear means nothing. All the other friction discs and steel plates measure fine as does the piston travel.
They are to get a parts list with some new bearings and seals as well as the worn friction and steel and expect to have it back in the machine this week.

 

[watglen]

What was the bill for this work multiracer?...just so I have an idea.

 

[Multiracer]

They are waiting for a few more parts from Cat that should be in today. The guesstimate so far including transport is between 6-8 thousand.
I will post here when it is back on my property.