ZD28 hydraulic drive problem

[longta359]

You should definitely test your fluid pressures before tearing it down. Kubota wants a small fortune for their test kit but I made mine for just a few dollars. Assuming you have determined where to hook up the charge pump pressure test from the WSM, remove that large Banjo bolt ( item #60 on the Hydraulic Delivery Pipe parts page). It can be drilled and tapped for 1/8" NPT pipe thread. Then all you will need is to adapt it to a hose and find a 1000 pound gauge. When finished with testing, install a 1/8" NPT plug. Checking the High Pressure pumps requires only hooking up a hose; the threads are standard tapered 1/4" pipe threads. It is pretty congested around those ports so I hoisted mine up and hooked up to the ports on the bottom. You will need a 5000 pound gauge for this.

Removing the Transaxle takes several hours to do but it's not terrible hard. You will need a cherry picker or hoist to remove it from the frame. Very awkward,

I thought my HST was toast on one side but pressure testing revealed that the HP Relief and Check valve was worn out and the spring was weak. I can just about assure you that if you take it to a dealer they will just install all new kit ($2K) and give you a $4K plus bill.

Sea Dog, if you are still out there, can you shed some light on the Test port you mentioned. I am trying to test using Position 2 per the WST, but I get 0 pressure from it. When removing the bolt, some fluid drains out, so I assume that there is not another bolt behind this. The threads on my port (the lower one) are#4BSPP. I can't find a tool to fit the top port. I have tried 7, 8, 9, 10 mm and 5/16, 3/8 allen wrenches.

 

[longta359]

Sea Dog, False alarm. I was looking in the wrong place. I found the port and it is 6 mm allen. It was hiding under the hydraulic line and I could not see it. Sorry to bother you. On the good side, the pressure was 3700 psi, so my drive is not bad yet.

 

[Pmschmitt]

Realized I never gave a final update. Got it all back together several years ago and has been running flawlessly ever since. Great machine glad I just went ahead and fixed it