TN75D Power Shuttle - Reverse Only

[drivinganh]

Hello,

I have a 2002 TN75D 16x16 4WD with a Power Shuttle is throwing fault code 41. The tractor will engage reverse but not forward. It was happening intermittently at first but has seemingly become permanent.

I've done a lot of searching on this forum over the past few days and found others having similar problems in the past, which were resolved with either a new ECU or Shuttle Switch.

One post said troubleshooting the ECU can be done by "check continuity at an unused pin at the ECU's connector and toss the ECU if that pin is shorted to ground"

Another post ended up having wires between his clutch pedal and clutch switch being wore down to metal and shorted to ground.

Another post said there was a service bulletin issued that the shuttle switch could be cause the fault

"AS PER THE REPAIR MANUAL, the 41 fault code does indicate a problem
with the forward solenoid or its circuit, not the shuttle . A properly
trained tech with a diagnostic tool or properly programmed laptop can
troubleshoot this circuit from the tractor seat. A loose, faulty or
improperly insulated shuttle switch can also trigger rogue faults
including 41. This info is NOT included in the service manuals as of
11/05, but has been disseminated in bulletin form."

I have not yet found a post that said replacing the forward solenoid solved the problem.

I do not have a repair manual, and am looking for some general advice on troubleshooting problem, as well as any diagrams people would be willing to share.

Diagrams (or information about) that would be extremely helpful:
Shuttle switch
ECU
Power shuttle

The posts I'm referring to are linked below:

http://www.tractorbynet.com/forums/n...e-problem.html
http://www.tractorbynet.com/forums/n...code-78-a.html
http://www.tractorbynet.com/forums/n...problem-2.html
http://www.tractorbynet.com/forums/n...o-forward.html

Thank you.

[Harry in Ky]

You might try a couple quick checks. The solenoid valves for the shuttle should be under the right floor plate. I think they are threaded in virtically, while the pto, dif lock etc are horizontal on the front side of the valve body. the shuttle valves should be the same part so they can interchange. Try swapping the coils from fwd to rev valves and see if the problem changes directions. If nothing changes, try swapping the wires between coils. This will send signal from your shuttle lever in fwd to the rev solenoid. Might help narrow down where the problem is coming from without buying any parts till you know what you need.

[RickB]

Remove the left rear wheel to access the transmission control valve. First check the shuttle lever assembly and make sure it isn't loose in its mount. A loose switch can short the contacts to ground. A & B solenoid coils mount at about 45 degrees from vertical. They can be swapped with each other, but not with any other solenoid coils you find.