Transmission problem...

dvto2

Member

Equipment
Bx23 and implements
Feb 26, 2019
86
8
8
east granby
Bx23 purchased 2003. I just did a repair on the steering cylinder, by replacing it. Steering was solved, and I did a little mowing. Went back out to do more after dinner and the hydrostatic transmission is acting weird. Tractor runs a few feet and then comes to an abrupt stop. Happens going forward and backwards. Steering works fine, mower blades turn, mower deck raises and lowers. I did not lose much transmission fluid when I changed the cylinder and the level is full. I never had this problem before. Any thoughts?
 

Motion

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Lifetime Member

Equipment
Kubota MX5100HST/FEL
Aug 17, 2020
524
289
63
Mandeville Louisiana
Was the HST having issues prior to the steering cylinder replacement? If not it's probably related, possibly air, is the fluid in the sight glass clear or foaming? I assume you kept everything clean when installing the steering cylinder, did you fill and vent the cylinder prior to starting the tractor? I'd suggest letting it sit for a day to let any entrained air settle out and recheck the level.
 

dvto2

Member

Equipment
Bx23 and implements
Feb 26, 2019
86
8
8
east granby
Did not fill the cylinder prior to installing. Dont know where the sight glass is. Letting it sit is one of the most hopeful fixes I can think of.

I did see a very slight seepage of fluid from the right hose compression fitting (right as your sitting on the seat). Not sure if I can get a wrench in there to try and tighten it.
 

DustyRusty

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Equipment
2020 BX23S, BX2822 Snowblower, Curtis Deluxe Cab,
Nov 8, 2015
5,251
3,878
113
North East CT
There is no sight glass on the BX23, only a dip stick located at the rear of the tractor. When was the last time you did a oil change on the hydrostat, and changed the filter? I recently learned about a dye that can be added to the hydrostat oil so it is easier to see on the dipstick. John Deere Original Equipment Hydraulic Oil Dye #MT3668, and it is claimed to be safe for all brands of tractors. If JD can market a green dye, there is no reason that Kubota can't sell an orange dye. Getting back to your problem, most likely air in the system that needs to be worked out. A low hydro oil level will not cause that type of problem, just running hot, which will eventually ruin your hydro.
 

Dave_eng

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Equipment
M7040, Nuffield 465
Oct 6, 2012
5,132
934
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Williamstown Ontario Canada
I think the ps controller may be the supply for the HST system.

Air is the likely problem.

I will now see if i have a WSM to confirm my recollection

Yes the ps controller feeds the HST + the pto clutch.

Cycling the pto clutch may help with air elimination......... a guess right now.


forum BX23 HST.jpg


forum BX23 HST 1.jpg


forum BX23 HST 2.jpg



It seems if you suspect air the last thing you want to do is try and use the HST. See above instructions after trans fluid change

Dave
 
Last edited:

dvto2

Member

Equipment
Bx23 and implements
Feb 26, 2019
86
8
8
east granby
So, I did operate the tractor after installing the steering cylinder. It had a small amount of the symptoms (some hiccuping in the acceleration), but I mowed for a half hour, then let the tractor rest an hour, and that's when I had the problem. I haven't tried it yet today. What s the best way to get air out of the system, assuming that's the problem. Or have I done something horrible to the hst?
 

dvto2

Member

Equipment
Bx23 and implements
Feb 26, 2019
86
8
8
east granby
My nephews own a kubota dealership, used to be my brother in laws. I reached out and talked to a mechanic who said 1) I should not need to prefill the cylinder, 2) that the steering and hst have their own pumps and changing the steering cylinder should not effect the transmission. Therefore, he thinks the problem is coincidental (one heck of a coincidence), and is either in the pedal linkage or the transmission itself (ugh). The linkage I can check but other than that it would have to go to the dealer. Their's is where I bought the tractor but it's 2 hours away, so no easy solutions there.
 

eserv

Well-known member

Equipment
BX24, A1000 Kubota Generator
May 27, 2009
2,115
113
63
Hardisty, Alberta
My nephews own a kubota dealership, used to be my brother in laws. I reached out and talked to a mechanic who said 1) I should not need to prefill the cylinder, 2) that the steering and hst have their own pumps and changing the steering cylinder should not effect the transmission. Therefore, he thinks the problem is coincidental (one heck of a coincidence), and is either in the pedal linkage or the transmission itself (ugh). The linkage I can check but other than that it would have to go to the dealer. Their's is where I bought the tractor but it's 2 hours away, so no easy solutions there.
The return oil from the steering IS the charge oil for the HST on a BX ( and some other Kubota models) so the steering and the HST are related. They are right though, that you shouldn't need to prefill the steering cylinder though it wouldn't hurt to do it. Running the transmission low on oil would be the most likely cause of a problem after repairing the steering cylinder. Or getting dirt or a piece of thread sealant into the system.
 

dvto2

Member

Equipment
Bx23 and implements
Feb 26, 2019
86
8
8
east granby
The pedal linkage seems fine. The tractor barely budges now - it's getting worse. Fluid still full. Seems like I need to get it to a dealer.
 
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