My L3901 seems WAY under-powered to me

[wagne223]

Are the brakes stuck applied?

 

[Paul12210]

I have several hydrostatic machines and I'm fully familiar with how hydrostatic machines work. I bought an L3901 a couple year ago and haven't used it too much (because, as noted, I have other machines). However, this year, I got the tractor out and it was time to see what it would do. Which, to my surprise, isn't much. To put it in perspective, I must run the tractor in low range for ANYTHING other than basic travel across mostly level ground. Even in mid-range, if I stop on a small hill, the tractor will barely take off. I'm aware the tram peddle is not a gas pedal...it operates more like a gear box...applying a little tram will give the most torque, etc. But the main thing convincing me the tractor may have a problem is its behavior. Specifically, I can't make the engine "bog down" under tram load. For example, if I try to start off on a hill in high range, the engine does not complain even though the hydrostatic transmission is whining away and the tractor isn't moving. Ether the engine has so much power it can engage the transmission pressure reliefs with ease, or the pressure reliefs are set too low (or, the transmission has a problem).

I'm posting to get the experience of some other 3901 owners. Does this sound normal to you? When in mid or high range, can you bog down the engine when attempting to take off or transverse on a hill that's too steep? Before I take the tractor in for service, or trade it for another model, I’d like to get an opinion as to whether this experience is normal for this tractor.

I have an L3400 HST -- it's a beast! Plenty of power. I usually move around in high (idling), medium for doing most work. The only time I use low is when I'm digging into a dirt pile with the FEL. Your experience sounds abnormal.

 

[DieselBound]

To answer some comments:

I have R4 tires and run the machine at 2800 RPM's (max power) most of the time.

Curious as to why you feel that you have to run at 2,800 RPM. I run 1,800 RPM when driving around; 2,200 RPM (or so) when doing loader most work; and, the required RPM for PTO work (about 2,400 RPM).

 

[crashz]

Like others have mentioned, my 2501 will spin the tires in low, 4wd by accident. Will spin 3 tires with the differential locked and pulling something heavy or stuck. In medium it will do that same, but I hear more whine and the engine seems to bog sooner.

I'd follow Rick's suggestion and go through the tractor for maintenance issues first. You said their aren't many hours on it, maybe it hasn't had the 50hr service yet? I was shocked when I pulled the hydraulic filter the first couple of times. This rig has a hydraulic (with magnet in the base) and trans filter and both may be clogged with shavings. I replaced the filters 4 times in 278 hours and the last one was clean of any debris.

 

[gejandsons]

I have several hydrostatic machines and I'm fully familiar with how hydrostatic machines work. I bought an L3901 a couple year ago and haven't used it too much (because, as noted, I have other machines). However, this year, I got the tractor out and it was time to see what it would do. Which, to my surprise, isn't much. To put it in perspective, I must run the tractor in low range for ANYTHING other than basic travel across mostly level ground. Even in mid-range, if I stop on a small hill, the tractor will barely take off. I'm aware the tram peddle is not a gas pedal...it operates more like a gear box...applying a little tram will give the most torque, etc. But the main thing convincing me the tractor may have a problem is its behavior. Specifically, I can't make the engine "bog down" under tram load. For example, if I try to start off on a hill in high range, the engine does not complain even though the hydrostatic transmission is whining away and the tractor isn't moving. Ether the engine has so much power it can engage the transmission pressure reliefs with ease, or the pressure reliefs are set too low (or, the transmission has a problem).

I'm posting to get the experience of some other 3901 owners. Does this sound normal to you? When in mid or high range, can you bog down the engine when attempting to take off or transverse on a hill that's too steep? Before I take the tractor in for service, or trade it for another model, I’d like to get an opinion as to whether this experience is normal for this tractor.

Starving for hydraulic fluid

 

[NCL4701]

I have several hydrostatic machines and I'm fully familiar with how hydrostatic machines work. I bought an L3901 a couple year ago and haven't used it too much (because, as noted, I have other machines). However, this year, I got the tractor out and it was time to see what it would do. Which, to my surprise, isn't much. To put it in perspective, I must run the tractor in low range for ANYTHING other than basic travel across mostly level ground. Even in mid-range, if I stop on a small hill, the tractor will barely take off. I'm aware the tram peddle is not a gas pedal...it operates more like a gear box...applying a little tram will give the most torque, etc. But the main thing convincing me the tractor may have a problem is its behavior. Specifically, I can't make the engine "bog down" under tram load. For example, if I try to start off on a hill in high range, the engine does not complain even though the hydrostatic transmission is whining away and the tractor isn't moving. Ether the engine has so much power it can engage the transmission pressure reliefs with ease, or the pressure reliefs are set too low (or, the transmission has a problem).

I'm posting to get the experience of some other 3901 owners. Does this sound normal to you? When in mid or high range, can you bog down the engine when attempting to take off or transverse on a hill that's too steep? Before I take the tractor in for service, or trade it for another model, I’d like to get an opinion as to whether this experience is normal for this tractor.

That sounds abnormal. You should have enough power in M to pull a hill with no issue unless, of course, you have some ground engaging something or are pulling a substantial load of some sort. Taking off uphill in H should bog the motor to some noticeable degree. L should spin well before bogging the motor substantially, period. Of course it is far from the biggest tractor ever, and like all machines it has its limits, but the behavior described is not normal.

We could discuss gear v HST and true farm tractors v utility tractors all day but it remains that the OP’s tractor is behaving abnormally.

 

[rScotty]

It seems to be only transmission related. If I put a heavy load on the front bucket, the steering is a bit "jerky" if I'm not moving. But that is normal per my local Kubota dealer.

I think we might have missed an important hint way back on the first page in one of the OP's follow up messages.

I'm talking about post #8 where the OP says his steering is a bit "jerky" if not moving. Then says his dealer says that is normal.
No matter what his Kubota Dealer says, that is NOT normal at all. Power steering is normally completely smooth lock to lock with or without a load.

Sounds to me like he has a hydraulic problem.
rScotty

 

[Larry Caldwell]

I highly reccommended this tractor to an institutional customer. I am distressed, because they hate it, saying as well, it is underpowered. A toy. Mostly they don't like the lack of loader lifting capacity. And the front snowblower keeps suffering costly repairs, for wear, not abuse.

Loader capacity depends on the loader, not the tractor. Implements, like a snow blower, do not depend on the tractor either.

The best HST range in hot weather is the one that lets you run pedal down. That opens up the wobble pump and pushes the most fluid through the cooler. In cold weather, 50% pedal will slow the fluid flow and let it get a bit warmer. The HST loses more HP to fluid loss if the fluid is cold.

Except for utility tractor work, you should be looking at 45 HP and up for field work. The HST hydraulics will take at least 5 HP to run, which is a big hit with a smaller engine. For stationary PTO work like running a mill or generator, I wish there was a way to disengage the hydraulic system, but no such luck.

 

[Larry Caldwell]

I totally get what you are saying, with a little caveat...stick with me. A hydrostatic tractor has the "equivalent" of first gear. That occurs when you're applying just a little tram. Under that condition, the pistons in the variable displacement pump move just a small amount of hydraulic oil on each turn around the swash plate. So, this generates a lot of power.

In high range, the PRV will pop and vent around the hydraulic motor because the system protects itself. If you want maximum pulling torque, use low range. You notice the HST transmission did not spin the tires, which it could easily have done. This is a case of a salesman who doesn't know how to operate the machine.

 

[Larry Caldwell]

With all due respect, I don't think so.

Drive ratio refers to gears usually. This doesn't work like an automatic transmission or CVT in your car that actually has gear ratios.

It's a hydraulic fluid pump that pumps constantly at a rate determined by RPM and it drives / turns a hydraulic motor. When you back off the pedal, you're letting more fluid pass through the bypass circuit and causing less fluid to be applied to the wheels. You can't do more work by applying less pressure. But you can take some load off the engine by applying less pressure because you're allowing for more "slip" between the engine and the drivetrain.

That's not how it works. The pump is a variable volume pump with a "wobble plate" that changes angle as you push the pedal. When the pump plates are parallel the pump moves minimal fluid. When the wobble plate is wide open, it moves the maximum amount of fluid. There is no bypass, unless the system gets to dangerous overpressure levels. Maximum torque and minimum fluid pressure levels are in low range. Minimum torque and highest pressure levels are in high range. I have never seen the OPD valve pop in low range - even heavily loaded ag tires will spin. In high range, the OPD will pop easily, particularly if the fluid is cold.