Kubota TG1860G Hydrostatic Transmission Rebuild 

Having a similar issue. I start the mower and the hydro works great until mid throttle. When you say 180 degrees do you mean unbolt the two Allen screws and turn the oval plate? Or is it the gear assembly inside that is 180?

The pumps sit in the fluid so they are largely self purging. I lifted the rear wheels and moved the pedal forward/reverse to drive the wheels without working them. Minute or two is all it took.

In-depth DIY Thanks for the reply! I got her going. I did see on some non-Kubota Trans purging videos that pulling and holding the bypass valve and cycling forward and reverse 5 or 6 times would do the trick. I did that and had good rotation as soon as I released the bypass valve. Put the tires back on it and gave her a yard test. It’s good to go!

The part list is completely dependent on what broke. If you want every single part check messicks.com for your model.

I honestly don't have a good answer since I've never done it, but I'd suggest finding a cheap donor tractor with all the parts you'd need instead of trying to find individual parts.

I bought most parts from Messicks, they were the only place that had things in stock or on order, and were true Kubota OEM parts. They are a bit on the expensive side, though. Ebay was another option for a couple parts. I got the diagrams from Messicks, Kubota's service website, or orange tractor talks forum. I used a synthetic ISO 46 grade hydraulic oil. It works well for both hot and cold temperatures. Ultimately the cause of failure on mine was not the gears or pump, but the axle bushing I replaced on the one half in the video. It broke into pieces (my guess is from a large sideways force such as skidding or pushing it on the side done by the previous owner), and sent metal fragments into the gears that then broke the gear teeth. If that bushing never broke, it probably would have been fine.

In-depth DIY mine is currently working and is doing well with 1015 hrs, I’ve changed the oil and so far so good. I assume that in the end the trans is working as it should?

@@rarnette73 Yes, it works well now, though it has less than 8 hours on it since the rebuild.

In-depth DIY here is the Hydro Gear manual for the transmission. Found it on line www.hydro-gear.com/3127f665a8_sites/hydro-gear.com/files/BLN-51259_P5.pdf

@@rarnette73 link doesn’t work?

To be honest I didn't think to make a video until it was going back together. The disassembly is reverse of the install. Basically, when you start taking things apart they will start falling out. Start with the bottom cover and pump cover, take the inners out there, then take the case bolts out and split it in half. At some point early in the process it becomes self guiding.

@@in-depthdiy2123 do you have an idea why I would be able to get movement after changing my fluid at low engine rpms but no movement at full throttle? I used the correct hydrostatic oil speced in the manual. Is the pump on the bottom supposed to have the notch facing the back of the gearbox? Thanks

@@brandonwritt4452 The pumps are directional since the offset is to one side, so if it's reversed it will not build pressure. Other possibility is something is not sealing and the fluid is leaking internally, such as past the pump rams, the pump cylinder surfaces, etc. I'd try flipping the external pump 180 degrees to see if it fixes the issue. If not, then it requires more diagnosis.

@@in-depthdiy2123 Ok Great thank you for the reply. I have a friend getting me a dealer manual as well to help with the proper re assembly of the pump. I know the transmission isnt junk because it works great but not all the way.

Are you talking about the black plastic "fork" thing at 34:20 ? That's the retaining clip to hold the pump races in place. The cover holds the plastic in place, the plastic holes the races. The magnet is just to collect metal debris and keep it out of the pumps and gears.

Yes, I've noticed my oil pump gears have timing marks , also noticed it has no oring in the groove, it pulls fine & doesn't leak, until I did a oil change , now it doesn't pull

Unfortunately I do not provide professional services.

~$500 USD

@@in-depthdiy2123 so that's how much it cost in parts? How long did it take you total?

@@in-depthdiy2123 I got one that needs to be torn apart, accessed. Not sure what the issue is first. It's slipping when it gets warm

@@collinscustoms Yes that was the total cost of parts for just the transmission. Total rebuild time was roughly 6 hours of work, spread over multiple days.

There's no kit, I bought all the broken pieces and new seals individually from messicks.

Hydro gear, most online dealers. look up 310-3000 manual at Hydro gears website. I researched this for a year before rebuilding my, The o-ring goes between charge manifold and center section. Mine was early version. It will suck air if put in the groove.

I don't do this professionally. Just hobbies I do in my free time. Parts alone to rebuild this one were ~$500 USD. New complete units are on the order of $3000 or more. So if I had to give a quote, I'd say between $500 and $3000.

@@in-depthdiy2123 3k fer that little thing wow they smoking good weed a 500 for parts is wild to unless it was most every thing i guess

@@overbuiltautomotive1299 $500 was for most of the internals. The only parts I did not buy were the pumps, casing, axles, and outer planetary gears. The spider and inner planetary gears, all seals, shims, bushings, and fluid were all bought new.

@@in-depthdiy2123 ok that would do it boy that thing was grinded up inside sounds like

No, you run the risk of putting the swash plate, pump, and internals out of alignment. The shaft holds everything centered and very likely won't go back together without disassembly.