2007 3520 Power Reverser won't move

[tuolumne]

3520 with 3000+ hours. Lots of loader work and woods work. Transmission has been flawless until now. There has been no slow change or accident; just sudden failure.

First, does anyone have access to a service manual?

This machine won't engage forward or reverse. The linkage is working fine (moves lever on the side of the transmission). The clutch linkage is fine. The machine starts fine (not safety switch). The hydraulics are working fine - loader and rear implement operate smoothly and with normal power. The 3 point lifts normally, but I cannot speak for its strength with no 3PH implement attached. All fuses are good.

The dealer suggested a relay - thought there should be one labeled PRT, but there is not.

Dealer suggested o-ring failure on hydraulic loop that engages PRT - said pressure could be checked at a plugged port on the transmission. Where is such a port? The dealer did not suspect solenoid since both forward and reverse are out. Does that ring true? I have not yet been able to connect with a service tech on the phone.

The machine had been operating normally, backed up to load logs on a forwarder, then would not move again. The forwarder can push the machine forward and back, so the rear tires are turning freely.

Please offer your suggestions to help us get this machine back into operation.

 

[tuolumne]

I have purchased the .pdf service manual. The diagrams make the PRT control valve appear to be entirely mechanical. If no pressure is arriving at the clutch pack (machine won't move) there appear to be 3 possible problems.

1-oil is bypassing to the sump in the clutch valve. O-ring problem?

2-oil is bypassing to the sump in the forward/reverse valve. O-rings? Is this less likely since forward and reverse are gone all at once?

3-no oil pressure is available because the pressure pump failed.

Am I missing a scenario? How do I diagnose which is correct? Have others dealt with any of these issues and have advice?

 

[Agvg]

Doesn't the manual have data on how to measure pressure in the system? That would be the logical start point.

 

[Zebrafive]

What about hydraulic filter, has it been changed? Maybe plugged.

Tech manual should show location of test ports. I ASSUME they will be on the reverser valve. I ASSUME there will ports for system pressure, forward pressure, and reverse pressure.


If you are able to email the tech manual pdf, send me a PM and I'll supply my email address. Maybe then I can help more.


I also assume the tech manual has steps to check the reverser.

 

[radios1]

check for a rusted, jammed up reverser cable. it that don't move, it will cause this.

 

[tuolumne]

The manual shows locations for the test ports and I am trying to rig up a pressure gage that will let me check these.

 

[tuolumne]

Test port for forward shows 280 psi (260-290 target) and reverse test port shows 270 psi. The test port for the lubrication pressure shows zero (same target). What direction do I look now?

 

[radios1]

Test port for forward shows 280 psi (260-290 target) and reverse test port shows 270 psi. The test port for the lubrication pressure shows zero (same target). What direction do I look now?

check for a rusted, jammed up reverser cable. it that don't move, it will cause this.

 

[tuolumne]

I have attached an exploded view of the PRT valve. The area that I circled appears to be the lubrication cut-off valve. I intend to take this out first. The "theory of operation" section of the manual is a bit over my head, but it appears that if this valve were stuck open the oil pressure could not build enough to engage the clutch. Any comments?

 

[Zebrafive]

I have attached an exploded view of the PRT valve. The area that I circled appears to be the lubrication cut-off valve. I intend to take this out first. The "theory of operation" section of the manual is a bit over my head, but it appears that if this valve were stuck open the oil pressure could not build enough to engage the clutch. Any comments?

Can you post the theory of operation page(s)? That might help us understand the operation and better comment on where to look.