Hydrostatic transmission stuck in fwd

   / Hydrostatic transmission stuck in fwd #1  

dan110

New member
Joined
Jan 20, 2018
Messages
3
Location
IL, TA
Tractor
meelo 27.7
Hi everyone!
I just got an old merlo 27.7 1995.
I rebuild the 1004 engine and start it on.
The problem is that the tractor stuck in fwd, slow speed, no matter what im trying to do. The backwards/forward not responding. Im showing you guys some photos of the pump.
Any ideas? 20171217_144512.jpg20171212_182553.jpg20171217_145209.jpg20171217_154843.jpg20180108_140822.jpg
 
   / Hydrostatic transmission stuck in fwd #2  
Dan,
There should be two electrical connections to the control on this pump. These connections are two solenoid valves that provide the input for direction of travel. Did you check to see if the command to these is changing when shifting from forward to reverse? I would suspect that one of the valves is stuck or that it is always receiving a slight voltage. The coils are 12 VDC.

There should also be a port labeled Ps on the pump. That is the pilot supply pressure for the control on this pump. I would estimate this pressure should be around 25 - 30 Bar. I would suggest installing a gauge in this port to confirm that you have pilot pressure.

If you do a search for Rexroth data sheet RE 92003 for European english or RD 92003 German this data sheet will help explain the DA1D3 control.
 
   / Hydrostatic transmission stuck in fwd #3  
Dan
I made an incorrect statement on Pressure in Ps port. With the DA1D3 Control the Pressure in Ps will vary with the travel speed command. There is linkage that connects to a valve in the control that will vary the Ps Pressure based on engine RPM and command from the linkage.

Port G is charge pressure and this should be in 25 - 30 Bar range.
 
   / Hydrostatic transmission stuck in fwd
  • Thread Starter
#4  
Hi again, thank you for your answer.

The two solenoids works fine, i checked them.
What is the "linkage" that you talked about it? I think this is the problem. Can you mark on the picture where it is?
Thanks.
 
   / Hydrostatic transmission stuck in fwd #5  
Dan
I believe the linkage connection is shown in the 4th picture of the complete assembled pump. Looks like an L shaped arm.
 
 
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