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Discussion Starter · #1 ·
Hi all!

I am starting to see some real lack of travel power on my Case 155. I am unable to determine if it is the gear pump, the hydro motor, or the control valve or some combination of them. They are all pretty old.

I am not looking for an exact answer, but curious to what others may feel the issue is based on experience, so I can narrow the choices I have.

The tractor has been in the family since the early 70s. When I took the tractor from my grandpa five years ago, I stripped it all, and rebuilt it. It was already lacking some power before I stripped it. However, 5 years later, it is getting pretty slow.

  • System has clean Shell Rotella 15w40.
  • Screen is clean.
  • Control valve linkage appears to be solid, and fully enters and exits the control valve. Note: there does appear to be some oil around that seal, but does not drip. Just looks moist. I am not certain if it is suppose to be like that.

  • Tractor has issues going up slight inclines in low gear. WOT is required to inch up the inclines. I live in suburbia, so the slight inclines are those for my side easement.
  • Tractor refuses going up moderate inclines. This is a slightly steeper incline of my rear easement. As soon as the rear tires get to the incline, the tractor stops. WOT just causes the tractor to jerk or lurch like it wants to move, but doesn't go anywhere.
  • If I go up either of these inclines with WOT and Mower Deck PTO engaged, the tractor will die unless I disengage the PTO or move the drive from forward to neutral (sometimes both).
  • Forward on low is slow, reverse on low is faster.
  • Forward on high is not much faster than low-slow (throttle has to be up higher), reverse is fast.
  • Speed going downhill on low is controlled (no speedup), Speed going downhill on high is uncontrolled (speedup)
  • Forward speed doesn't really do anything until I move the lever to full forward. Reverse starts to see movement as soon as I move the level towards reverse.

  • Char-lynn Control Valve. Original
  • Char-lynn Hydro Motor (i believe). Original. I disassembled this completely. There was some general wear on the flat surfaces. I machined these surfaces flat again. No noticed difference in performance.
  • Borg Warner Wooster DIV Gear Pump #P25AH21R01. Unknown if this is original. Date stamped 11/66. This may be from a 195 at some point. Unable to find any specs for this pump.

  • I do not have a gauge to test PSI.
  • The control valve test/drain screw is seized. I wasn't able to even get this screw off when I had the control valve off and in a vice. Testing PSI at this port will not be possible at this time.

Notes: Motor was bored at some point in the 80s, so it now makes 12hp instead of 10hp. Motor is strong, runs and idles smooth.

I know there is an aftermarket hydro motor. Is there an acceptable aftermarket gear pump that can be purchased today that is recommended by other 155 owners? Is there aftermarket control valve or seal/spring kits recommended by owners of 155s? I am willing to purchase any and/or all to get this tractor to full power potential again. It has sentimental value.

Thank you for those who read and respond.

Tractor Whisper
3,703 Posts
Its time for drive motor.
While into changing drive motor lines off get one cap and fitting to use pressure gauge on port valve. That away get by froze drain/test plug so set relief pressure. IF set pressure and hold pump still good if needle goes up to pressure setting then falls lower need new pump. Pressure never go to high setting check the pressure relief spring for breakage.
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