JD 3720 CUTS HST Sluggish

[jenkinsph]

Oldtink
Maybe, but my 4300 HST is responsive to forward and reverse pedal at any rpm, including idle. just sayin...

All three of my hst tractors are responsive at idle, increasing the rpms certainly increases the travel speeds though.

 

[4570Man]

I could drive any of my HST tractors at idle, but they work much better at higher RPMs. My F2560 will drive at idle, but it's unable to lift the deck which is hydraulic.

 

[Beltzington]

Update - I finally was able to adjust the Motion Match (MM) setting, had to order and replace my broken turn signal rocker switch which I never use but it is how the you raise or lower the MM settings if your tractor does not have a dedicated MM switch. Kind of hard to explain but the MM settings do not really effect how fast the tractor moves but how abruptly it starts and stops moving. At idle with MM set to 1 (most aggressive) it still seems sluggish at idle. I spoke with a very experienced mechanic and he said this is not uncommon as the hydro pump and valves will loose efficiency over time and more RPMs will be required for the tractor to move as it did when new. He also said not to worry about it as it will likely be 1000+ more hours before I would need to start considering rebuilding or replacing the pumps.

 

[Deere Dude]

Update - I finally was able to adjust the Motion Match (MM) setting, had to order and replace my broken turn signal rocker switch which I never use but it is how the you raise or lower the MM settings if your tractor does not have a dedicated MM switch. Kind of hard to explain but the MM settings do not really effect how fast the tractor moves but how abruptly it starts and stops moving. At idle with MM set to 1 (most aggressive) it still seems sluggish at idle. I spoke with a very experienced mechanic and he said this is not uncommon as the hydro pump and valves will loose efficiency over time and more RPMs will be required for the tractor to move as it did when new. He also said not to worry about it as it will likely be 1000+ more hours before I would need to start considering rebuilding or replacing the pumps.

I think another experienced service man is in order.
I have 650 hours on my 3720 and everything was working great then all of a sudden the tractor would barely move at idle and wouldn't jump to life until 14-1500 RPM then works fine at higher RPMs. But if driving along at high RPMs and bump it to 1000 RPMs the tractor would slow way down, much more than before, almost to a crawl.

I would think if the pump was going bad it would go bad progressively, but seems coincidental that yours seems to act the same as mine, unless I read something wrong.

I stopped into a JD dealer here and got a lot of head scratching but one mechanic said I should may try cleaning the inline hydraulics filter. It has another 100 hours to go before I think I should but as soon as I get a couple gallons of oil I will try that. He said there might be something in the inline filter. He also said I should drain the oil and fill with diesel and run it a while with that in. I really hate to do that, but am beside myself trying to figure this out.

The tractors speed is to hard to regulate now unless you want it wide open, or at least faster than 1500 RPM, but I need to go very slow and idling in some applications.

 

[chubby]

Same thing with my 3720 but not my 3120. Same thing bump to 1500 works fine at idle just about inop. Been like this since around 150 hrs. I assumed that the smaller engine without the turbo kicking in was the issue since the bigger displacement 3120 was fine. But the in line filter=check valve might be the ticket. In 30 hrs I will know and share answer.

 

[RollTideRam]

You can clean the inline filter without loosing any fluid.

 

[Deere Dude]

You can clean the inline filter without loosing any fluid.

I was told by a mechanic at a dealership my problem and he said to clean the inline strainer but all the fluid would be lost. I just need to ask, "Are you sure," and if so is there a particular method to it other than to unscrew it and take it off?

 

[Oldtink]

That's surprising. I cleaned my inline filter on the 3520 and didn't loose more than a cup of oil the whole time the lines were disconnected while I sprayed off the element. BTW the filter was spotless upon disassembly at approximately 500 hours and is the first time I inspected it. It of course didn't change anything as far as not moving at idle....
just say en

 

[Deere Dude]

That's surprising. I cleaned my inline filter on the 3520 and didn't loose more than a cup of oil the whole time the lines were disconnected while I sprayed off the element. BTW the filter was spotless upon disassembly at approximately 500 hours and is the first time I inspected it. It of course didn't change anything as far as not moving at idle.... View attachment 487750
just say en

Did you change that think while the transaxle was still full of fluid?

It does sound like a plan though. I'll try that first. The dealer must have gotten his wires crossed somehow.

 

[RollTideRam]

You might would loose all your fluid if your tractor is upside down. The filter is on the side of the engine. The cartridge filter in the sump under the tractor.