My L3901 seems WAY under-powered to me

[Pks]

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.

Check your hydrostatic filter, they have been known to be plugged with lots of chips on the outside of the filter before the oil goes in that's what the magnetic ring is all about. Also check the oil level in your hydrostatic transmission body. If it's low it might not be picking up any oil.

 

[Fallon]

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).

Because that's what in the owners manual & recommended by the manufacturer. Not just a Kubota thing either. Most manufacturers recommend that for Tier 4 engines with a DPF. Higher RPMs minimize the soot output & how often it needs to do a regen.

 

[Red Eye]

Responses in the last few posts have identified the problem. Not enough oil going to the primary pump. Kubota has had this problem for years. In my L6060, if you work on hills, you will be frustrated. Going steep uphills the tranny jerks like someone playing with a clutch pedal, whilst the steering locks up so you can’t steer. Also, oil runs out the back fill port and goes all over the back end of the machine, and the dust makes this quite the sight. Talking to the dealer, he said to over-fill the trans will help. OK, yes it does, but on a hill, the oil just runs out all the same. You’d think Kubota would make a tractor that was designed to be used on hills. Nope. Used on flat land it’s just fine. As for your problem, I would change the filters and be sure you have lots of oil.... like waaaay up the dipstick.

 

[SDT]

Responses in the last few posts have identified the problem. Not enough oil going to the primary pump. Kubota has had this problem for years. In my L6060, if you work on hills, you will be frustrated. Going steep uphills the tranny jerks like someone playing with a clutch pedal, whilst the steering locks up so you can’t steer. Also, oil runs out the back fill port and goes all over the back end of the machine, and the dust makes this quite the sight. Talking to the dealer, he said to over-fill the trans will help. OK, yes it does, but on a hill, the oil just runs out all the same. You’d think Kubota would make a tractor that was designed to be used on hills. Nope. Used on flat land it’s just fine. As for your problem, I would change the filters and be sure you have lots of oil.... like waaaay up the dipstick.

I have no such issues with my L6060 though I have some very steep hills.

That said, having stall guard and Auto HDS on at the same time will cause a bucking bronco effect when climbing hills near power limit.

No, I do not over fill my sump.

SDT

 

[Tony H]

My tires are filled and I keep the tractor in 4wd all the time along with a tiller on the back for counterweight. It does NOT want to spin the wheels in low, never mind mid-range. I've had a few times digging soft dirt (wash near my creek) and it didn't want to spin the tires at all in low. Since the tractor is fairly new (less that 100 hours) and I generally don't want to abuse my machines by creating cavitation in the hydraulic pump, I backed off and took a lighter bite. Again, this is low-range. Maybe I'm just too gentle and need to lay the whip to it. However, I KNOW it will not spin in mid-range. In fact, I rarely use mid-range because it's seems so under powered that I don't want to cavitate the pump.

Just in case someone is wondering, I know how to use a hydrostatic powered machine. When under load, only apply the tram necessary to get moving, not pedal to the metal. Yes, it's a touchy-feely thing...not enough tram and you don't move, too much and ether the engine (should) start to stall or you push the reliefs into by-pass. But this tractor has no sweet spot. I stopped the other day on a mild slope in mid-range. As I engaged the tram, it did nothing but whine. The engine did not idle down at all. I had to shift into low.

This more descriptive post does not sound normal. My L Kabota can spin tires when using FEL into a pile of dirt. Move in slow in Lo or Mid and I can spin tires before lifting load if I push it in too far. Having said that, I usually just go right to lo when tilling or anything other than travel.

 

[jonsstihl]

The OP hasn't come back yet But my vote is that the Parking brake is on. or a hydraulic issue who knows what could have happened while it was sitting.

 

[Industrial Toys]

It actually makes sense that people that don't understand the variable displacment HST pump, would just mash down on the peddal if things were getting tough, as they would on a vehicle's throttle.

I like my HST on the Kubota wheel loader. Throttle peddal is somehow connected to the HST. But this machine doesn't have any PTO to keep at speed either.

 

[Beeenvenue]

Another possibility is a detent remote stuck “on”. Can be hard to notice and would cause these symptoms.

 

[marrt]

Thanks for all the comments guys. I still haven't had a chance to dig the L3901 out of the barn yet (it's stuck behind some other equipment) and I had some family issues to deal with this week.

As to some of the other questions...

The tractor has about 100 hours (I'll update) and I did the 50 hours service early and replaced all filters and the hydraulic fluid (with Kubota's Super Ultra Expensive Fluid 2 or whatever they call it). That used to be standard with Kubotas...replace the fluid at the 50 hour service. Not sure if it's still required or not but better safe than sorry. The level is correct.

The parking brake/brakes are not engaged.

I don't have any hydraulic remotes.

Regarding the "jerky" steering, this is a different pump than the variable displacement pump. If I recall correctly, the steering pump is shared with the bucket lift circuit. However, I was not lifting the bucket when steering. But I agree that this should not be "jerky." It doesn't happen all the time so I live with it.

I drive at full rpm's to avoid too many regens. I have 3 machines with DPF's and I hate DPF's. Primarily because equipped engines inject fuel on the exhaust stroke during regen. Some of this fuel can end up in your oil...which dilutes the oil. After a regen, you should always check the oil level (I don't but should). I have a Takeuchi TL-8 compact track loader and had to replace a small part on the DPF...VERY expensive.

I will try to get over to the barn tomorrow and dig out the tractor, test it, and report back.

 

[Fallon]

Thanks for all the comments guys. I still haven't had a chance to dig the L3901 out of the barn yet (it's stuck behind some other equipment) and I had some family issues to deal with this week.

As to some of the other questions...

The tractor has about 100 hours (I'll update) and I did the 50 hours service early and replaced all filters and the hydraulic fluid (with Kubota's Super Ultra Expensive Fluid 2 or whatever they call it). That used to be standard with Kubotas...replace the fluid at the 50 hour service. Not sure if it's still required or not but better safe than sorry. The level is correct.

The parking brake/brakes are not engaged.

I don't have any hydraulic remotes.

Regarding the "jerky" steering, this is a different pump than the variable displacement pump. If I recall correctly, the steering pump is shared with the bucket lift circuit. However, I was not lifting the bucket when steering. But I agree that this should not be "jerky." It doesn't happen all the time so I live with it.

I drive at full rpm's to avoid too many regens. I have 3 machines with DPF's and I hate DPF's. Primarily because equipped engines inject fuel on the exhaust stroke during regen. Some of this fuel can end up in your oil...which dilutes the oil. After a regen, you should always check the oil level (I don't but should). I have a Takeuchi TL-8 compact track loader and had to replace a small part on the DPF...VERY expensive.

I will try to get over to the barn tomorrow and dig out the tractor, test it, and report back.

Kubota manuals spec changing the hydraulic oil at 200 or 500 hours forget which. Only the hydraulic filters need changing at 50. No harm in changing all the fluid, other than to your pocket book though.

Most tractors either have 2 hydraulic pumps or 1 pump & a splitter. 1 runs steering, the other the loader, 3pt & any other hydraulics. I think Kubita has 2 pumps or a single pump with 2 circuits/chambers. All of that is completely separate from any HST pumps.

My L4060 grand can run out of fluid when I try to turn fast & cause a bit of a hiccup. Think my L3200 did too. It complains a lot when turning with a heavy load on the loader. Proper 3pt ballast helps unload the front axle & minimize the groaning. I go gentile on steering lifting heavy. Front axle parts are expensive & it's way weaker & more complex than any rear axle.