Yes, i think so. Bolted to rear hst assembly. Been reading mixed views on hst screw...whats your thoughts....should i screw in and out to try and free piston and see if speed improves? Was considering marking then screwing in to test, then return to original if no difference. Also tempted to remove, strip, clean and reassemble. Stories of O rings getting worn/sticky.
Kubota RTV 900 transmission problem - hardley moves in gear!
- Thread starter PACKASAURAS
- Start date
aurthuritis
Well-known member
i would probably count the threads and measure precisely the length of the screw so i could put it back to the same location. even though you can't be sure it hasn't been messed with it still gives you a baseline. then i would start adjusting it and trying it often to see if it helps. i wouldn't be afraid to take it off as an assembly then on the bench take it apart and clean it up and check for sticking or blocked passages. if that helps then i would have the balance adjusted by the dealer.
aurthuritis
Well-known member
sorry try to attach an image and can't do it
Looks very serious without rear box! Discovered exhaust was broken too....!! Played about with screw and wheels started moving in reverse, when accelerated they would revert to forward motion however still maintained previous speeds. Put screw back to original position*. Managed to get it off (few photos attached). Everything seemed to move freely when worked by hand and looked clean enough inside, however I noticed a tiny rust mark in the piston bore and relating mark on O ring, so maybe it was stuck and binding. Cleaned all with WD40 and in process of putting back on. *I did notice they the screw is barely touching the piston - does this sound right? Also noticed that horizontal pivot hammer head is not symmetrical - is this worn or standard? No evidence of debris in oil/inside case. If anything jumps out at you from photos/text please let me know. Thanks again
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aurthuritis
Well-known member
how does it run now? that rust ring doesn't look that bad. the piston that does all of the moving is the long skinny one. the big one is really more of a plug that is supposed to put pressure on the long skinny one to aligned it with the ports in the valve block. did you compress the spring to make sure that part was all free?
Spring appeared to be too strong for me to depress manually when out but when back in i activated arm and it was springing back. Now all bolted back on but doesn't appear to be springing back like when it was out... Should it spring back? Opened up adjacent chamber to check it was it correct guide and it appears to be. Should chamber be filled with tranny oil? Thanks
aurthuritis
Well-known member
oh also should note that the piece in the photo is just the spool valve. the servo piston is in the adjacent box that the lever from the spool actuates. did you check to see if the servo piston was free?
the spool takes the input from the speed control lever and uses hydraulic pressure to even and smooth the control. then the lever from the spool actuates the servo piston and that actuates the swash plates giving control to the positive displacement pump and motor and this translates to more or less speed. i don't think your swash plates are getting full travel.
the spool takes the input from the speed control lever and uses hydraulic pressure to even and smooth the control. then the lever from the spool actuates the servo piston and that actuates the swash plates giving control to the positive displacement pump and motor and this translates to more or less speed. i don't think your swash plates are getting full travel.
aurthuritis
Well-known member
sent you a PM check your inbox
aurthuritis
Well-known member
yes that is the servo piston. it should move freely. no need to fill with oil as the charge pump fills this and excess is drained back into the tranny case. look at the PM look at A. and B.
oh i said freely but it boes have an internal spring. but it should move under hydraulic pressure. i see a polished ring on the servo piston indicating it has moved at some time.
oh i said freely but it boes have an internal spring. but it should move under hydraulic pressure. i see a polished ring on the servo piston indicating it has moved at some time.
Thanks for diagram, very useful. That profile cylinder in last photo is solid and will not rotate or slide. Tried gentle force with a section of soft timber but nothing budged. Could this be the issue? Is it supposed to rotate as well as go in and out? Maybe that is why "hammer head " is worn ? Thanks
aurthuritis
Well-known member
yes that is your problem. question>> are pins 5 and 4 in the diagram sheared off? can't tell in pic but the feedback lever 7 should be at a 90 degree angle to the control lever 6
aurthuritis
Well-known member
yes. but are the pins damaged bent or loose? the feedback lever looks like it is worn on one side were it engages the servo piston. if the piston was seized and someone forced the control lever it may have bent or broken the pins. thus everything is grossly out of adjustment. the control and feedback lever need to be firmly at 90 degree no slop
aurthuritis
Well-known member
in your photo of the spool assy the feedback lever is against the housing and the control lever looks like it isn't against the cardboard and not at 90 degree to the feedback lever.
aurthuritis
Well-known member
not sure what you need yet. the servo piston can be removed pretty easy but you need to remove the spool just like you have already done so the feedback lever isn't engaged in the piston. then just remove the four bolts that hold the cap on the servo and pull the piston out of the bore. it rides on orings and one could be bad. an easy fix. but have you answered the previous question?
aurthuritis
Well-known member
problem found. when you move that lever it should move the spool and the servo in a controlled relationship with one another i think the stem into the drum that the pins attach to may be stripped or the pins may be sheared.