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9760 STS Gearcase Pressure Warning **See Post for detailed problems**

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#1 ·
Hi All,

I Have a 9760STS Has been working well all harvest.. stopped at end of run to engage the Rotor... Was a very smooth engagement as it engaged and was spinning at 40 RPM then 5 seconds later the Gearcase Pressure warning light/alarm turned on.

Rotor disengaged and low idle no worries
Mid Idle no light but Hydro drive dies when trying to move more then quarter movement on the hydrostat
High Idle Light/Alarm Turns on after about 2-3 Seconds Move to low idle no alarm

Engine coupling appears fine spin the main pulley and motor turns over
Gearcase Pressure pump test Seems to check out with stats in the book
Regulated pressure test 219Psi (175psi in the book)

No filter restriction light on (Have not changed yet as it doesnt seem like it would be plus its a 2 hour round trip to closet dealer)

Has anyone else ever come accross the above or any help in diagnosing it (the jd repair manual is a bit vague since nothing matches the problem)

Regards
A farmer with 125Ha Left of Harvest :cautious:
 
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#5 ·
So you're saying you can't get the rotor to spin faster than 40rpm? I missed that. The switch or the sensor wouldn't cause that.
What do you consider the main pulley?? If you have any functions at all you engine coupler hasn't let go.
I'm not totally sure what your problem is but I would check the stacked pumps on the backside of gear case.
 
#6 ·
Yes rotor wont go over 40 rpm.. I have now lost steering... I pulled the pump stack apart there is a bit of wear on the seals but nothing untowards that would cause problems i cant get any relief pressure on the pump and in the process of reassembling the pump stack I damaged the oil seal in the stack so currently trying to track that down to reassemble then plan is to change the filter just incase lack of flow then burn the fkn thing

Engine coupler appears fine turn it by hand and the motor turns over
 
#8 ·
Just making sure. So if that coupler sheered you'll have no hydraulic or drive functions whatsoever. It's a thrill when you see that $500 chunk of rubber that runs everything.
I think its possible that coupler could sheer and grab somewhat for a bit. Although doesn't seem likely. I guess once you get that gear case pulled, (and pretty sure we removed the outer half of the separator drive) you can see what the gear case spins like. Had one go around 3500 eng hrs on a 9770. Fixed it in the field. Wasn't the worst job. It is probably a littler simpler on the 70's because of the changeup of the chopper drive without all those hoses running through that chopper drive support.
 
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