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barehill · 06-03-2020, 10:04 AM

Revived RV for spring and it will not shift out of Park with engine started, foot on brake.
To troubleshoot I disabled the drive shaft parking brake (removed linkage, which was free). Discovered that this model (Oshkosh X-line) has hydraulic actuator to apply this brake. A valve assembly is mounted under the actuator cylinder but I can't figure it out from here. Manual says: "The parking brake is applied by means of a control valve activating a relay valve which activates the spring-set parking brake chamber. The spring brake chamber pulls a cable engaging the drum brake on the transmission drive shaft."

I'm lost where to look next. The Shifter on the dash has two cables, one goes to the transmission, the other to where? Its not easy tracing these things!

Some other problems this spring: alternator not working (repaired); engine fuel shutoff solenoid stuck (repaired); ignition switch failed (apparently, instrument lights stay on requiring fuse removal and re-insertion to start engine)

Any help appreciated.

Oshkosh XC18RD chassis
Tiffin Allegro Bay Pusher (1994)

jergle · 06-03-2020, 10:13 AM

Can be faulty brake light switch, or some vehicles have an actuator near the shifter (safety mechanism to prevent shifting into gear without brake pedal being applied) that can go bad. There may be a "bypass" button that allows you to shift when that actuator goes bad. Check your owner's manual.

garykk · 06-03-2020, 11:05 AM

Does this Mh have a push button panel or regular shifter? You mention cables, do you mean wires.
Sounds like the transmission is not seeing the brake signal. Like was mentioned, check the brake switch.

short kid · 06-03-2020, 04:50 PM

Can you put the key on and shift to neutral without starting? On m y previous gasser with a Ford engine and trans with a blown brake light fuse I couldn’t get it out of park with the engine running cause of the safety switch.

barehill · 06-05-2020, 04:01 AM

Thanks everyone for suggestions.

The shifter mechanism only has two cables, one goes to the tranny. This cable works so the-can't-shift-out-of-park must be related to the other cable. There are no brake interlocks or other solenoids/switches/sensors with this shifter mechanism.

Tracing that cable from the front to the rear of the coach was tricky and inconclusive. So I traced the hydraulic hoses from the park brake control valve over to its control valve. This valve was tucked along the chassis frame, hard to find and difficult to examine. I put my hand up there to feel around and there is the end of the shifter cable I was looking for! Feeling further I realized it was jammed. WD40 and a screwdriver prying the linkage solved the problem! Now it shifts freely out of park to any gear.