D9H Transmission Issues

My D9H, 90V9144, won’t move. Machine began to hesitate shifting f to r, then ceased to move. Checked pressure of tans pump and it was 420 at priority valve on front of trans, 0 on P1 and 110 on P2. Checked mag screen and it was full of aluminum as was oil, I removed and replaced torque as it has failed. Replaced filters, cleaned all filter housings torque hoses, cleaned priority, relief, and pressure control valves. Changed trans oil, Shell Spirax TO-4.
I still have no pressure at P1 and 110 at P2, and tractor won’t move. I have 420 at priority valve port. Trans will shift into all gears but the ujoints never slow down, transmission isn’t engaging. I removed the ripper valve and rear cover and the transmission main shaft is turning but not the pinion output.
I am at my wits end and would appreciate y’alls input. I am a new member but I have looked at threads here for a while. Hoping Nige sees this as he probably has forgotten more knowledge than I will ever know.

P1 is speed clutch, should be 300 psi min./345 +/-10 psi. max. P2 is Direction clutch, should be 55 +/-8 psi less than speed clutch pressure. I'd say you either have an oil supply problem (leakage) or a clutch leakage problem.

Thank you for the reply.
I agree it’s an oil supply/pressure issue. What’s puzzling me is how it happened all of a sudden. I found nothing but aluminum in the screens and filters, no iron no bits of seals etc. Could the pressure control valve be worn and bypassing. It looked and felt ok but I don’t have specs on it. What are your thoughts on flushing the system with diesel to try to remove any trash that may have something stuck open.
Also, the brakes do not feel like they have much resistance.

"All of the sudden" tells me that a chunk of something has bypassed the pressure filter and plugged/stuck a valve somewhere. I'm betting in the trans control valve itself. 30 years ago I had a 992B do about the same thing, in the trans control valve there was a spool that had a floating spool inside of it with a .030" orifice... A small chunk of rubber hose liner shut the whole works down. I don't have the manual to tell you where it is, or what it is. And it may not be the same valve. I just remember it was a PITA to find.
And no, I would not do the Diesel fuel flush. Change pressure filters by the hour... Yes.

My first thought would be the priority valve. With 420 going in and no apparent feeling in the brakes, because everything that's acting up is downstream of the PV.
However as OM has pointed out the fact that you have 0 in the Speed Clutch but 110 in the Direction Clutch would appear to indicate something's leaking in the tranny, because if the PV was playing up surely P1 & P2 would be similar..? Low, yes, but broadly similar to each other. I think you've got contamination from the TC failure still hanging around somewhere.

Is there any way of pressurizing the transmission clutches with compressed air to try to detect an internal leak..?

I've attached the specs for the Priority Valve. Do you have a Service Manual for the tractor..?


FLOW OF OIL (SCHEMATIC)
1. Left brake band. 2. Left brake booster. 3. Oil filter. 4. Oil pump. 5. Magnetic screen. 6. Oil cooler. 7. Steering clutch piston. 8. Oil lines to brake hydraulic mechanism. 9. Steering clutch and brake hydraulic control valve. 10. Priority valve. 11. Torque converter outlet relief valve. 12. Brake cooling and lubricating oil pressure relief valve. 13. Right brake booster. 14. Right brake band. 15. Transmission lubrication oil manifold. 16. Bevel gear case reservoir. 17. Transmission case. 18. Scavenge and circulating oil pump. 19. Torque converter.

Did you operate with the transmission cover off and note if there is leakage from the o-ring sealed hydraulic connector tubes? or any other major leaks?
Other valve checks...
Pressure relief valve in the hydraulic control valve stuck open.
Check valve stuck in bore.
Pressure relief valve spring broken.
Differential valve sticking closed.

Hydraulic controls for steering clutches and brakes are fed prior to the priority valve.
The pressure tap on the priority valve indicates transmission oil pump pressure. The P1 tap is beyond the priority valve. If you have good pump pressure and nothing at P1 tap the priority valve function would be suspect.

Thank you for the replies.
RZ the valve is in the top of the trans and does have a floating spool, I have removed and cleaned but wonder if it may be out of spec and bypassing.
Nige, thanks for the specs. I do not have a service manual. Since you sent the priority valve would you happen to have one on the pressure control valve handy.
The only way I know to pressurize the system is to remove the pressure control valve and both shifting valves to expose the tubes in the transmission. I haven’t gone this far as I don’t turn wrenches for a living and am not quite that confident in my skills as I’ve never been deeper than the shifting valves in the trans. That’s one reason I wanted to make sure I’ve checked all I can, as I really don’t want to drop this trans. Converter is one thing, trans is another animal.
Is there anywhere to check steering clutch and brake pressure to isolate whether it in those systems or the trans.

Yes OM. Operated with cover off and noticed no leakage. I had replaced the orings when I cleaned the pressure valve. Trans “spits” when shifting speeds, but not direction. Fluid is moving in trans as it does splash out from the rear of the top with the cover off.
There were no broken springs in the pressure valve but I keep going back to the pressure valve due to the shifting hesitation the day it quit moving since pump pressure checks out.

I’ll get the spec for the pressure control valve but it won’t be until tomorrow I’m afraid.

Thank you Nige, tomorrow is fine. Thank you all, the help is greatly appreciated.

I could post the parts diagram for the PC valve if that helps but I don't have the specs.

Thank you OM, but I have the parts book with diagram.

Clean the protective valve spool and adjust inside linkage on direction valve spools and speed spool.
Bob

As promised.

Thank y’all, I appreciate the help and input.
Bob I assume you mean pressure valve spool.

Vcutter said:

Thank y’all, I appreciate the help and input.
Bob I assume you mean pressure valve spool.

Click to expand...

No its the shift valve or direction selector valve inside the transmission and that linkage.
bob

Just an update, cleaned priority valve again and swapped out pressure control valve from a 46A donor we’re parting out and tractor is moving again. Thank everyone for their help and insight.

I have a couple questions as I don't know the answers
1st. Have any of you experienced going from forward into reverse and it goes forward but not very often this has happened only a few times
try it again and it works fine the rest of the day every shift seems great and quick maybe adjustments? or ?
2nd. How much pressure should be on the tube assembly from the tranny to the filter housing #36 page 62e ( part #9s4737 )
mine sprung a leak where its pressed into the 90 degree elbow that holds the o'ring attached to the tranny filter housing.
It was a pain to get to this steel tube out for removal and reassembly we took it to get it silver solder but they missed the leak its a drip now should have gone all around the pipe, so going to try to do it again this time with out pulling the line all the way out
one guy told me it has about 500 psi, I wont run it with the drip as it could get worse dont need a fire.
I had to tie rags around it to keep it from spraying on the exhaust- turbo. just to get to a spot to work on it.
this just so happens to be on a v blade d9h also.