# Bolens HT 20 Transmission issues



## G:sson (Nov 25, 2019)

I have a question relating to Bolens HT 20 tractor mod. 2087 that's been running for years but recently hydro transmission started to behave differently.
The hydro is a Sundstrand 90-1143 RH and the problem is that the acceleration forward and reverse is jerky. From being kind of smooth it now kicks in with full power even if the pedal is pressed carefully.
Consulted a Sundstrand manual suggesting oil & filter replacement as a first step. I am using fluid and filter from John Deere as this was the only supplies I could find near me. Fluid and filter replacement didn't improve anything.
Further into the manual I found the section related to acceleration valves that caught my interest, page 21 in the manual.
Took the valves out for inspection and visually they seem ok but have a question. Can anyone by looking at attached photos let me know if it on my type of valve is possible to unscrew the cap to inspect the internal spring and ball. I did not try as it seems solid as it looks like one unit. In one of the valves the internal ball is not moving so freely as in the other suggesting a possible cause for my problem? Is the direction of the flatted section of the valve important when put back in place.
Any other suggestions how to proceed?


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## G:sson (Nov 25, 2019)

Update on the problem
Managed to open up both valves by removing the cap on top. Then its possible to take out the internal spring and ball. Polished the inside of the valve and the ball. Cleaned the spring as well and re-assembled both valves and put back in place. Turned the valves 45 degrees as the manual indicates. Not really sure if this is important.
I also took out the charge relief valve for inspection and it was clearly visible on the valve cone that this valve was internally leaking. Placed the valve in the turning machine and very carefully machined and polished the cone to remove the grove. Put valve back in place.
Started the engine and checked for leaks but all ok. Noted that my work with the valves for some reason had moved the neutral position so wheels turned in reverse. Adjusted the neutral position and put back the seat for a test drive.
To my surprise the function of the hydro gear is back to normal or in fact like new. Runs very smooth at any engine rpm. Problem solved.


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