1760M Hydrostat trans. surging

[bglegal1]

2019 1760M Cab. 215 hours. Last weekend using the tractor to move some brush/logs around, after 45 minutes or so, the transmission started surging in reverse. Forward was completely normal. Surging was not too bad, but noticeable for sure. No loss of engine RPM's. Was able to finish what I was doing with no problem other than the surging in reverse. Mostly nothing on the loader in reverse. I'm at a loss as to why it only happens in reverse. All scheduled maintenance has been timely done. Before I start changing filters, fluid, etc. anyone else experienced this? Any suggested fix or areas to troubleshoot? Thanks

 

[oldnslo]

Is the hydrostatic trans electronic controlled on that model? If yes I would suspect a problem in the electronic control circuit more than the hydrostatic trans especially since operates fine going forward.

Reason for this thought is that the Main components of HST are the same for both forward and reverse.

 

[jeepcj7]

Does it do it when the hydraulic oil is cold or only after it reached operating temperature?

 

[bglegal1]

Does it do it when the hydraulic oil is cold or only after it reached operating temperature?

I’d been running 45 min or an hour. Outside temp was in the 80’s so believe it was up to operating temp.

 

[lpakiz]

I've noticed my 1754 doing that in reverse. It's more noticeable when in 4-wheel drive.

 

[GrandpaSmurf825]

When you say it's surging do you mean it's slowing down and speeding up as you travel backwards? Some manufacturers will restrict reverse travel speed for safety. Does this travel the same speed in both directions? Does it make any difference what range you are in?

If it uses and electronic controller and it appears it does, it might need to be recalibrated. That's usually a pretty straight forward process . You will need a digital multimeter to do this if you want to undertake it yourself. They typically have a "pot" or potentiometer on both sides to regulate the voltage to the coils. Controllers can also fail but this is the first step in diagnosing it. The specific process for this should be in a service manual.

Does it seem less responsive or predictable in reverse? As in does it not always start off smoothly or as you increase how far you depress the pedal does it not seem to respond and then will respond suddenly with a speed increase? These are indications of the controller at minimum needing recalibration.