Gehl 6635SXT no hydraulics

[shewelt]

While moving a light load of dirt, heard a snap/clank, then nothing. No hydraulics to lift/tilt or drive functions. Engine runs, just no hydraulics. It's dead in the field. I'm guessing the gear-pump failed, but only a guess based on reading. Hydraulic level is good, clean fluid, filter was replaced 8 hr's ago on the hr-meter (in March). Any way to check other then pulling the pump? Any advice on pulling the pump, do I need to drain the hydraulic tank or can I attempt to bag / plug the inlet line to stop flow while replacing the pump? What else could it be if it's not the pump (common to all functions). I've only had this thing less than a year, so don't know that much about them yet. It's a 99 6635SXT 2-speed / 80hp. Any advice appreciated. thanks...Scott

 

[shewelt]

Todays update: Pulled the hydraulic gear pump & disassembled. Looks fantastic inside. So convinced it's not the hydraulic gear pump. Something else I did while I had the pump apart. I re-inserted the gear spline shaft back into the tandem-pump (where it usually goes when pump is re-assembled). I found I could rotate (not easy, but could rotate by hand) the shaft & hear everything basically rotating in the tandem pump. Now I'm wondering if it's suppose to be able to rotate by hand, or should it be mechanically fixed coupled to the engine, thus not free-spinning unless the engine rotates? Does everything in the tandem pump rotate as a fixed unit or do things engage / disengage from the internal shaft leading to the pump. My guess is the shaft should be locked with the engine so the pump spins, providing hydraulic pressure when engine is running. Next question, is there some sort of drive coupling connecting the tandem pump with the flywheel on the engine? If so, has anybody replaced one? Can I do it by detaching the tandem pump at the flywheel / engine bell-housing without pulling the engine? This thing is sitting in my field, a distance from my shop, and at 4 tons, no way to easily get it back to the shop. Any help appreciated...thanks

 

[Tazza]

Todays update: Pulled the hydraulic gear pump & disassembled. Looks fantastic inside. So convinced it's not the hydraulic gear pump. Something else I did while I had the pump apart. I re-inserted the gear spline shaft back into the tandem-pump (where it usually goes when pump is re-assembled). I found I could rotate (not easy, but could rotate by hand) the shaft & hear everything basically rotating in the tandem pump. Now I'm wondering if it's suppose to be able to rotate by hand, or should it be mechanically fixed coupled to the engine, thus not free-spinning unless the engine rotates? Does everything in the tandem pump rotate as a fixed unit or do things engage / disengage from the internal shaft leading to the pump. My guess is the shaft should be locked with the engine so the pump spins, providing hydraulic pressure when engine is running. Next question, is there some sort of drive coupling connecting the tandem pump with the flywheel on the engine? If so, has anybody replaced one? Can I do it by detaching the tandem pump at the flywheel / engine bell-housing without pulling the engine? This thing is sitting in my field, a distance from my shop, and at 4 tons, no way to easily get it back to the shop. Any help appreciated...thanks

My guess is the linkage from the engine to the pump went. There will be a coupling of some sort joining the two, never worked on one, so i can't tell you for sure what it is/

 

[shewelt]

My guess is the linkage from the engine to the pump went. There will be a coupling of some sort joining the two, never worked on one, so i can't tell you for sure what it is/

Finally had a chance to update: After more dis-assembly on Sunday, found it is actually one of the shaft couplings between the 2 tandem servo's. It's a fine-pitch coupling & the splines are wore flat. So it's a $35 part, but took some disassembly to get to it. Gehl # 123114 COUPLER. Much better than a $500 gear pump! I looked all over the internet for any information of a 6635 with similar experience by a Gehl owner and found nothing. Hopefully this helps somebody else in the future, because I'm easy on my own equipment, so assuming this has to happen to the guys using company equipment. It's possible they just take them in for service. I'd have to guess with towing this would have been a $1500 service fee. I'm guessing it will all go back together in ~2 hr's. Took longer coming apart because had to figure out how/what needed to be pulled to access the area. Part should arrive today. #36 was the coupling that failed if you check the parts book for the 5635/6635/6640 etc. PS: There is another coarse-pitch coupling that connects the tandem shaft to the gear-pump, it was fine, but be aware if somebody else has this issue, could be the other coupling or the shaft itself. Looking at ~4~5hr's to get to the point I did to find the issue.

 

[Tazza]

Finally had a chance to update: After more dis-assembly on Sunday, found it is actually one of the shaft couplings between the 2 tandem servo's. It's a fine-pitch coupling & the splines are wore flat. So it's a $35 part, but took some disassembly to get to it. Gehl # 123114 COUPLER. Much better than a $500 gear pump! I looked all over the internet for any information of a 6635 with similar experience by a Gehl owner and found nothing. Hopefully this helps somebody else in the future, because I'm easy on my own equipment, so assuming this has to happen to the guys using company equipment. It's possible they just take them in for service. I'd have to guess with towing this would have been a $1500 service fee. I'm guessing it will all go back together in ~2 hr's. Took longer coming apart because had to figure out how/what needed to be pulled to access the area. Part should arrive today. #36 was the coupling that failed if you check the parts book for the 5635/6635/6640 etc. PS: There is another coarse-pitch coupling that connects the tandem shaft to the gear-pump, it was fine, but be aware if somebody else has this issue, could be the other coupling or the shaft itself. Looking at ~4~5hr's to get to the point I did to find the issue.

Glad it was an easy fix, make sure you give it a cood clean to get any metal shavings out of the pump. You don't want any metal eating the pump up.
Thanks for passing on the details, i'm sure someone will find it helpful.