The right side drive engages after the control lever is moved about a quarter of the way forward or backward. It has a lurching effect which is quite undesirable. The left side works fine. Any ideas as to what may be causing this? Any help would be greatly appreciated.
You need to start with the control lever bushings, the ball joints on both ends of the neutral control rod, the centering spring adjustment, the cross shaft bearing and bushing, the shock absorber and ball joints on each end, the control rod and ball joints to the servo control lever from the cross shaft, loose lock bolt on the servo adjustment bracket. This is just a starting point, simple checks of things that if worn or loose will cause issues to not allow it to handle/respond well.
:iagree As the movement at the actual control valve on the pump is very small compared to the movement on the control levers any play in the linkage will be magnified by the time it gets to the pump. It all comes down to starting at the basic stuff before looking for the other possible causes.
I put the machine up on blocks, and disconnected the control rods at the top of the pump. I can move the control for the left side slightly in either direction, and the wheels will start creeping slowly. The control for the right side must be moved a considerable amount either way before those wheels will turn, and when they do engage, they start turning at a speed proportional to the position of the control rod. In other words, I cannot get the right side wheels to turn slowly like the left side does.
Look closely at the small control arm at the pump. Is the slot in the lever that engages the spool worn? If there is wear there due to a loose retainer, you will have similar symptoms. Apart from that you may have a sticky servo piston, which is a little harder to fix.
Check alrman's suggestions first. Is this a recent issue, or has it always done it? If its recent you may have leaking servo seals, or broken spring guide. If its always done it, someone may have installed the servo control spool backwards (item 26).
This problem started about 6 months ago. I also noticed the maximum speed on the right side is slower than the left side. The pump was rebuilt about 8 years ago.
Sounds like weak pump or motor. Maybe leaking servo seals. You can check servo pressure at the plug on the servo. (item 4) Should be equal to charge pressure, around 300psi, with lever fully stroked.
I will ckeck the pressure, and post the readings.