L35 GST shift problem

bcrockar

New member
I have developed a "no reverse" problem on 1998 L35 with 1250 hours. Machine has had multiple owners but has been very reliable for the 200 hrs I have owned it.
Symptom is the shuttle shift lever feels blocked when reversing. Going from neutral to forward engages normally. I have removed covers on steering column and verified the linkage is free. There has never been any binding or difficulty with shuttle shift to date. I have verified that hydraulic fluid is at proper level and both pumps seem to operate as usual. Gear shift will engage all speeds OK. 3 point operates fine. From the shop manual I have determined the forward / reverse shift is a mechanical shift that triggers the hydraulic clutch. The shift fork can be accessed by removing GST valve housing on side of transmission.
It appears the GST valve can be removed with out removing frame rail but it will be tight and not provide good access. Does any one have experience with this problem or removing the GST valve?


Conditions at failure: I had taken a loader of dirt up a moderate hill and dumped. I pressed clutch and coasted back down to flat (distance of 20' - 30' ). At that point I could not shift to reverse ( clutch still depressed - never released ). This is something I have done several times in the past with no problems Shift lever will go to neutral but blocks before it gets to a comfortable center.

I find "forward only" operation less fulfilling than "forward and reverse".

Thanks for any insights.
 

irwin

Member
Have you by-pass'd the linkage and tried to move the valve into reverse directly? Just interested if you've ruled the linkage out that way.

Let us know what you find..
 

bcrockar

New member
Yes I have verified linkage is not a problem. This was accomplished by removing the linkage completely ( leaves 1" of shaft protruding from top of transmission).

Once I had the linkage clear I elevated and rotated one rear tire to spin gears in transmission. It went into forward with no problem. When moving to reverse while rolling tire I could feel the teeth touching slightly but shaft (Part 4 on diagram) stopped turning at that point. It seems the fork rod is blocked from full travel in the reverse direction ( B direction on diagram).

I had conversation with mechanic at dealer who has seen cases of the shuttle shift linkage being pulled upward bending the tab that keeps the Shuttle shift Arm in transmission. This caused reverse to be blocked is some cases. Sorry to report this is not the problem with mine. The Shuttle shift shaft is free but not sloppy.


I also answered my own question on removing GST valve assembly without disassembly of tractor. There does not seem to be enough clearance from the frame rail to allow removal.

Strategy now is to move tractor to shady spot, remove the rear tire and frame rail to gain access to valve plate.


Keep the comments/questions coming.
 

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irwin

Member
Thanks for the quick update bc. I'm watching this thread (anyone with GST should) please keep us informed...

Hopefully this is one of those problems caused by a springball, loose lockscrew or a bushing (read, something easy) at the access cover and not something more catastrophic.

Fingers are crossed for ya.
 

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bcrockar

New member
root cause of problem: one of three synchronizer keys had jammed in protruded position blocking shift into reverse. It appears one end of key was thrown outward by centrifugal force and jammed. See attached photos of shifter in reverse, neutral and forward.


prevention: only coast while shuttle is in neutral or don't coast at all. My unit failed while coasting backward with shuttle in forward. While the shuttle is in neutral the keys are covered and cannot be moved by centrifugal force. Coasting in low range could possibly spin the shifter faster than normal operation in high gear.

Without disassembling gears I could not determine if the keys were worn or springs weak. I also considered contaminated oil, but did not see anything in the bottom of case or in drained oil that looked out of place.

I am thinking of reassembling and giving it a try. I realize this problem could happen again without warning. At that point I will order shifter, keys, springs and split cases for repair.


Are there any other thoughts out there on what to do while I have it apart?
 

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irwin

Member
root cause of problem: one of three synchronizer keys had jammed in protruded position blocking shift into reverse. It appears one end of key was thrown outward by centrifugal force and jammed. See attached photos of shifter in reverse, neutral and forward.


prevention: only coast while shuttle is in neutral or don't coast at all. My unit failed while coasting backward with shuttle in forward. While the shuttle is in neutral the keys are covered and cannot be moved by centrifugal force. Coasting in low range could possibly spin the shifter faster than normal operation in high gear.

Without disassembling gears I could not determine if the keys were worn or springs weak. I also considered contaminated oil, but did not see anything in the bottom of case or in drained oil that looked out of place.

I am thinking of reassembling and giving it a try. I realize this problem could happen again without warning. At that point I will order shifter, keys, springs and split cases for repair.


Are there any other thoughts out there on what to do while I have it apart?

Hope that did it for you bc, and thanks for posting this thread.. good warning for me and others with GST.
 
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