Ok, i can now answer my last question - you do not need to drain oil - drained or not you will always loose 1 litre or so when opening block (so be prepared to catch it!). I couldn't resist trying drive again before opening up hst block again....and i got drive! Same as pre repair, circa H-10mph, M-7mph and L-5mph. Still going to change valve plates to avoid damage caused by damaged valve plate, however what else could be causing slow drive? New valve plates are showing some light scoring but trust this is expected due to rotating parts?? Some refer to faulty charge pumps - where is the charge pump or is that not where i am working on? Also perhaps pressure relief valve..any more ideas? What are the hex keys top and bottom of hst block - should i open and clean them out? Sorry for any silly questions, as said previously this is all new to me!! Thanks again, David
Kubota RTV 900 transmission problem - hardley moves in gear!
- Thread starter PACKASAURAS
- Start date
scoring was probably a result of no assy lube. new plates are a good idea and your experience hasn't been wasted. since you basically have the same performance after the rebuild i would probably check or just replace the charge pump. i think on your model the charge pump is behind the suction filter. you might want to make sure you don't have any restrictions in the suction circuit, like a hose that collapses when running. could also be debris in the pressure relief valve. before you disassemble the relief valves you need to put a set of gauges on the diagnostic ports first.
Thanks very much for reassurance. I've traced the hoses from around suction filter housing and they appear to go the radiator under seat and engine?? Is this just a "coolant jacket" for oil? Which hoses do i need to check are not blocked? Managed to get broken bolt out (phew!!). Thanks again.
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yes you are correct. that is an oil cooler or really an oil warmer also. check the online partsbook and you will find a schematic and find the pump under that filter. i am not sure about the disassembly and reassembly of that pump so not sure if it needs to be done before you install plates or not. if i remember in an earlier post you said you had the pressure checked and it was 100 lbs. you didn't mention if that pressure was at 1400 rpm with hot oil or not. you should read up on the charge pressure spec and measurement procedure before you proceed. i know the pressure is dependent on viscosity,temp and RPM. if you meet all requirements and have adequate flow but pressure is low then your problem is most likely in the valve. if you have low pressure and low flow then the pump is leaking. does that make sense???
http://www.nettractortalk.com/forums/showthread.php?t=17216
read this^^^^ if your charge pressure is 100 psi then look at above post
read this^^^^ if your charge pressure is 100 psi then look at above post
http://www.nettractortalk.com/forums/showthread.php?t=15432&page=4
another good read. go back a few pages on this thread^^^^
i also went back to confirm your earlier statement that your charge pressure was 100 PSI.according to this thread that would be a very good reading indicating your charge pump is OK so don't tear into it. now it looks like your servo control might have a sticking plunger. keep following the trail.
another good read. go back a few pages on this thread^^^^
i also went back to confirm your earlier statement that your charge pressure was 100 PSI.according to this thread that would be a very good reading indicating your charge pump is OK so don't tear into it. now it looks like your servo control might have a sticking plunger. keep following the trail.
Thanks very much. I think i said before that movement doesn't seem to coincide with acceleration. Revs are quite high (almost 50% pedal down) before movement is experienced in wheels, but then acceleration tops out preventing further speed. I've read some posts warning not to touch the servo screw, is the plunger behind this? What do i need to do to "free it off"? Thanks again, David
i think if it were me i would reassemble with new plates and before i did anything else i would check to see if the linkages that control the foot peddle to the HST lever and the throttle are all in correct adjustment. it would be a shame to further disassemble anything if all was wrong was it was out of adjustment. then i would confirm the high pressure was within spec.
the swash plate is not actually connected direct to the foot peddle. the foot peddle connects to the servo valve and when you step on the peddle you pull or push the lever on the servo valve. inside the servo valve is a piston that has equal pressure on both ends until you move the lever and the pressure differential moves the floating piston that has a lever that internally connects to the swash plate. so if your linkage isn't moving the servo lever full travel the result would be slow speed. now on the other hand if the speed lever on the servo is moving full travel but the piston inside is sticking, then the swash plate isn't being moved allowing the pumps to work to their maximum. this function is to keep us from killing the engine with to much peddle to fast. as the pumps pick up volume the increase puts more differential on the piston and the servo moves the internal lever that moves the swash plate in accordance with internal pressure. does this make sense?
Thanks again. The dealer was previously suggesting a new hst block, swash plates etc to resolve - have i now ruled this out? Another thing I did notice was a brownish "tide mark" on the inside of the block - is this a tell tale of anything? The block, swash plates etc all paper in good order otherwise. Is there a way i can manually activate the swash plate piston to determine if full drive is not being transferred to it? When new plate valves are in can i start up and manually fully activate the swash plates/drive to attempt to achieve top speed, this helping diagnose situation? Perhaps i need to call dealer back in and update him following valve plate replacement and request further pressure testing and focus on piston? Thanks
from the looks of the oil in your previous posts i would say the mark is probably a rust line from when the rtv would sit and the water would separate and rise. this would also indicate a sticking plunger. you can't directly move the swash plates,thats what the servo valve does. i know you don't want to spend more money on this and i don't blame you so be careful. i did quite a bit of googleing the subjects rtv 900 servo valve and also rtv transmission problems. i found some really good information with good photos and descriptions of servo valve adjustment and repair. might spend some hours study and proceed to remove the servo valve and as you disassemble pay special attention to the wear surfaces between the piston and barrel. always turn the adjustment screw in until it gently bottoms and record the turns so you can at least put it back to where it was. i don't think centering the servo is that difficult and can be gotten pretty close and close enough that you will know if the pumps will perform. then after you have done that you can have the dealer do a final adjust with the gauges if it turns out positive. just use assy lube and a new gasket everywhere. maybe that way you can get things going and make a good judgment on the overall condition without spending a ton of money.
before you disassemble the servo you might jack up the rear wheels off of the ground and start the engine and allow the hst to warm up some before putting the tranny in gear. then cycle the peddle between low and high while tapping on the piston area of the servo. the combination of hot oil and pressure might break it free. then with the engine off you might adjust the servo screw in until it bottoms and then back out. just remember to count the turns. repeat starting warming tapping then engine off and adjusting to see if the number of turns increases or decreases. this would indicate the servo piston is moving but still stuck. also record the speedometer ranges because if you gradually get more travel from the servo piston it will show up in more speed.
Thanks very much Aurthuritis. Lube Gard Dr. Tranny GREEN Assemblee Goo ordered off ebay and waiting on new valve plates to arrive (also changing all bolts and gaskets). Can I be sure the back up of dirt/debris is not in the pump (we suspected suction filter was full of dirt restricting flow-as when changed things improved). Please see attached photo - do I gently tap metalwork at end of screwdiver to try and free piston, whilst in gear and engaging drive? Many thanks, David
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you are welcome David. yes that is the servo valve and yes tap on it there. can't be sure about gunk in the system but i think the filter would trap most of the damaging stuff. you can kind of establish further damage by the original condition of the plates. also the charge pump must be ok and that is a good sign also. the charge bypass is working because you have good pressure there. you won't know about the positive displacement pumps and motors until you get further in. but i would reckon that your chances are pretty good you don't need a new tranny. i hope your problem is in the servo.
Thanks again, however I don't think the link answers my query. There are two transmission filters and only one is a "suction filter" (I think?). On my machine the "suction filter has been fitted on the rear filter housing but I am wondering if this perhaps should be on the side housing...unless they are different threads/sizes? I looked up codes on Messicks to pair up but my the codes on my filters (genuine Kubota) are different. Maybe i have wrong filters? Would this impact severely on performance?
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My yellow filter is on the side and the white is in the back on my 2011 RTV 900xt. That s the way it was on my 2005 also- after they changed the color of the rear a few years ago- it used to be orange. I don't remember the numbers off the top of my head but the last 2 digits was a 70 and an 80 on the other one... I think thats the way it is as.... I haven't looked in a while .. collie
i sent the link because there is a good visual on the placement of the filters. the yellow filter should be on the side and the white filter should be in the rear. you can check messiks parts numbers to confirm your filter number and location on machine.