Help! Mighty Mouse Nibbled Kryptonite Maybe

[SPYDERLK]

My BX1500 has a serious problem. Everything on the tractor is working perfectly except the transmission. Im running SUDT and the level is right - fluid clear and clean. Never a problem until yesterday when I noticed that pushing the go pedal for reverse in hi range caused the tractor to shudder. Forward fine - lo range fine both directions. Went ahead and got a good start on snowthrowing. Finished today and its getting worse. You have to really nurse the go pedal to get it to climb a hill or push - even in lo range. Once the tractor encounters a bit of real resistance the go pedal will just drop to the floor as if it lost its servo connection to the transmission and the tractor loses all thrust - it seems to be out of gear. If you let up and re press the pedal it has firmed back up and if you nurse it by pushing gently you may be able get enuf thrust to crawl out of the situation. Reverse is worse - the tractor wont back up much of an incline.

Does anybody know where to look for this problem? Iv heard of something called the charge pump that I think is necessary to supply the servo link to the variable volume hydrostatic pump. Is that correct? Why would it suddenly take a walk?

Ill get to looking for the obvious in a few minutes when the caked snow melts off. Boy I hope this is accessible from external.
Thanks,
larry

 

[EE_Bota]

Sorry to hear it. I don't know much about your tractor. Mine is a BX2200, and if they are alike:

If any of the hydraulics works, the charge pump must work. If the power steering works, then the flow priority valve is working. If the PTO works, you have fluid to that point, leaving the only thing between the charge pump fluid and the final destination: the PTO relief valve, and the FILTER. I would replace the filter if you have not already, since the filter is the last thing before fluid enters the axial piston pump / motor housing.

After that, I would start to wonder if some sort of contamination was interfering with the three relief valves in the hydro set.

 

[oldnslo]

My BX1500 has a serious problem. Everything on the tractor is working perfectly except the transmission. Im running SUDT and the level is right - fluid clear and clean. Never a problem until yesterday when I noticed that pushing the go pedal for reverse in hi range caused the tractor to shudder. Forward fine - lo range fine both directions. Went ahead and got a good start on snowthrowing. Finished today and its getting worse. You have to really nurse the go pedal to get it to climb a hill or push - even in lo range. Once the tractor encounters a bit of real resistance the go pedal will just drop to the floor as if it lost its servo connection to the transmission and the tractor loses all thrust - it seems to be out of gear. If you let up and re press the pedal it has firmed back up and if you nurse it by pushing gently you may be able get enuf thrust to crawl out of the situation. Reverse is worse - the tractor wont back up much of an incline.

Does anybody know where to look for this problem? Iv heard of something called the charge pump that I think is necessary to supply the servo link to the variable volume hydrostatic pump. Is that correct? Why would it suddenly take a walk?

Ill get to looking for the obvious in a few minutes when the caked snow melts off. Boy I hope this is accessible from external.
Thanks,
larry

Larry,

I would check the linkage between the foot pedal and the transmission. Look especially close and the connection on transmission. From what I can see in the parts list it has a pin that hold the linkage onto the input shaft of the tranny. This is the only simple and external common component I can think off that would give the symptoms you are describing.

Typically stuck relief valves should only effect travel in one direction.

Did you notice and excessive or change in noises coming from the tranny. I.e whistling like water fluid escaping under pressure?

Does the tranny get hotter than normal or get hot quicker in one area.

Good luck

Roy

 

[SPYDERLK]

Thank yous for the rational and reasoned responses. The transmission does not get hot at all. Its doing almost no work and the temp is below freezing... No noises either except associated with the shudder when right on the verge of the malfunction and the power stops and starts repeatedly causing a chatter sorta. The filter is making a lot of sense because the malady is less sensitive to elicit when 1st started after sitting awhile and develops as the tractor runs. Almost as if the filter pleating is closing up under sustained flow. I noticed further, that if I lift the 3PH while backing it is worse. Ill be off to the tractor store and report back later.
larry

 

[EE_Bota]

Perhaps there is water crystals in the fluid blocking the filter, or the viscosity of the fluid is high enough to cause trouble passing through the filter media.

As for the number of relief valves, my manual shows that there are three associated with the pump/motor set alone, and more than that throughout the system. One for forward direction, one for reverse direction, and one for the ultimate dump of charge fluid back to tank. I may have misinterpreted this somehow, however.

It is hard to keep from worrying about it, I am sure, but I would not become too worried until the tractor exhibited the behaviour with a fresh filter, and warm hydraulic oil. We all see a rash of problems on TBN during very cold weather.

 

[Bird]

I'm bettin' Roy (oldnslo) is right about the connection at the tranny. Sounds like a pin missing.

 

[curtisfarmer]

Afetr 1500 hours, 1 of my 2 L48s experienced real "slowness" (more than the known HST slowness) which I traced back to the pin and worn bracket to the HST pedal. Night and day now, and I would try the linkage as noted.

 

[SPYDERLK]

OK. A brand new filter helps but doesnt cure. I ran it around in hi range a good bit. Another thing I noticed is letting off completely on the pedal for "braking" going down hill can send it into a freewheeling mode - hydraulic coupling is lost. I can see this being very dangerous under the wrong circumstances -- but a clue just the same. When the pedal goes dead [no control] the pto clutch remains engaged -- and the 3ph lift operates normally. In fact, it almost seems the operation of the 3ph lift actually resets the pedal in that case so it works again. Also, problems seem to be worse at full throttle than reduced throttle. .........Any more ideas?? I wonder if this is going to go away when the weather warms.
larry

 

[Volfandt]

From the BX23 WSM, should be applicable to the BX1500 HST.
Good luck.
Dave

 

[kuboman]

Sounds like maybe the charge pump is on the way out.