mongoosetoo
Member
Moved this to a new thread from "Gehlk HL2500 Transmission" because I have a new problem now...
From the last thread, bought a broken skidsteer, left hydrostatic transmission drives fine, right side no drive at all. Took it all apart and found a broken input shaft on the right side. Replaced the shaft and here we are.
After reassembly. started machine, and neither side drives. Figured I needed to bleed air from line, so I disconnected lines from just as they exit the spin on filter and filled the lines manually with a syringe. Started machine and still nothing.
Next step, I removed the covers from the mechanical drive side of transmission and saw the tanks were almost empty. The way this hyd system works is it sucks hyd through the filter @ 5" hg, uses whatever fluid it needs and dumps the return fluid into the mechanical drive tank. Once the tank gets about 6 inches up, there is a big return port the fluid spills into and gravity feeds back to the main reservoir.
With the mech drive tanks empty, I figured it couldn't hurt to fill them up to the gravity return level. After that, I pulled the bleed screws on the hyd trans until I got flow, then put them back on. Took a 30 min lunch break, then fired up the machine and the left side began functioning as it should. Right side still did not function.
Continued troubleshooting and saw that with the engine running, the right side mech tank empties out back through the pressure side. My only explanation is the left side must be pulling fluid from the right side instead of through the filter - probably because there is less resistance. Thinking this must be a check valve issue, and not having any spare parts on hand, I swapped the check valves from left to right, and right to left. Bled the air out and started the machine again. Same condition, left side works fine, right side not.
While I had the hydrostatic unit apart, I inspected the charge pump and it seemed fine. And I should mention I was an aircraft hydraulic/pneudraulics specialist in the Air Force for a couple decades. I am rusty, but I understand most of the concepts still.
I am going to order a new filter, but right now I think it will not make a difference. I suspect I have a faulty Charge Pump. What are your thoughts? Thanks!
This post was edited by mongoosetoo on 07/07/2022 at 09:48 am.
From the last thread, bought a broken skidsteer, left hydrostatic transmission drives fine, right side no drive at all. Took it all apart and found a broken input shaft on the right side. Replaced the shaft and here we are.
After reassembly. started machine, and neither side drives. Figured I needed to bleed air from line, so I disconnected lines from just as they exit the spin on filter and filled the lines manually with a syringe. Started machine and still nothing.
Next step, I removed the covers from the mechanical drive side of transmission and saw the tanks were almost empty. The way this hyd system works is it sucks hyd through the filter @ 5" hg, uses whatever fluid it needs and dumps the return fluid into the mechanical drive tank. Once the tank gets about 6 inches up, there is a big return port the fluid spills into and gravity feeds back to the main reservoir.
With the mech drive tanks empty, I figured it couldn't hurt to fill them up to the gravity return level. After that, I pulled the bleed screws on the hyd trans until I got flow, then put them back on. Took a 30 min lunch break, then fired up the machine and the left side began functioning as it should. Right side still did not function.
Continued troubleshooting and saw that with the engine running, the right side mech tank empties out back through the pressure side. My only explanation is the left side must be pulling fluid from the right side instead of through the filter - probably because there is less resistance. Thinking this must be a check valve issue, and not having any spare parts on hand, I swapped the check valves from left to right, and right to left. Bled the air out and started the machine again. Same condition, left side works fine, right side not.
While I had the hydrostatic unit apart, I inspected the charge pump and it seemed fine. And I should mention I was an aircraft hydraulic/pneudraulics specialist in the Air Force for a couple decades. I am rusty, but I understand most of the concepts still.
I am going to order a new filter, but right now I think it will not make a difference. I suspect I have a faulty Charge Pump. What are your thoughts? Thanks!
This post was edited by mongoosetoo on 07/07/2022 at 09:48 am.