HST Power Loss on Kubota Grand L3940 HST+

[crazyal]

On the steep parts I have to be above 2500 with no attachments to drive up in in H and H-DS in fast.

 

[wmonroe]

I just came in from plowing the driveway and completely forgot to try the stall guard, guess I'll just have to get it back out tomorrow.

 

[rbargeron]

For people like me who don't know much about HST+ with H-DS, there's a good summary here. It has automatic load-sensing shifting similar to a car, but still with multiple gear speeds and operator-selectable automation modes. Loader work is different than mowing, and an operator can still select an inappropriate shift mode that bogs down the engine.

Future development of Kubota transmissions will likely keep engine rpm in a narrower band, with more continuously-variable output over a wider speed and load range, all under automatic control. Have your checkbooks loaded and ready, sports fans. Meanwhile, us dinosaurs will still be grinding gears :thumbsup: .

 

[The Fred]

For people like me who don't know much about HST+ with H-DS, there's a good summary here. It has automatic load-sensing shifting similar to a car, but still with multiple gear speeds and operator-selectable automation modes. Loader work is different than mowing, and an operator can still select an inappropriate shift mode that bogs down the engine.

Future development of Kubota transmissions will likely keep engine rpm in a narrower band, with more continuously-variable output over a wider speed and load range, all under automatic control. Have your checkbooks loaded and ready, sports fans. Meanwhile, us dinosaurs will still be grinding gears :thumbsup: .

CVT in most cars is junk. Short lifespan and if you tow you reduce the lifespan more. A wheel coated in rubber is hardly my idea of a good tractor transmission. Direct shift or computer controlled shuttle might be more like it. Have you driven a new Volkswagen with a DSG direct shift transmission lately? That's my idea of a future tractor transmission.

Anyhow back to HST, I noticed on mine that once I did the turbocharger and got the power up you don't need the features of the HST. Just hit the pedal and go. Still have never used high gear yet. My drive is too steep and with tire chains it'd be messy going fast.

Fred

 

[Gary Fowler]

I have been using my brother in laws NH to feed his cows lately since he is feeling poorly. What I noticed with his HST is that it performs poorly at less than about 1800 rpm. It will stall the motor and has very little pulling power at less than 1500 rpm with empty tractor and a bale of hay on the front spike. MY Kubota works even at idle and never actually stalls the engine when using the HST even in H range. I rarely rev the engine on it past idle to back it out of the shed. I can work HST, hydraulics etc at idle and they work good whereas his FEL hardly moves at idle. I guess some HST transmissions just work a bit different. I always wondered why he reved up his engine so much just to ease back when hooking up to a 3 point hitch, now I know.

 

[rbargeron]

CVT in most cars is junk.......

Agreed - I wasn't saying CVT, I said "more continuously variable" which in my mind means more gears with intermediate sliding-ratio planetary sets - like the ZF 8-speed now offered on high-ticket cars. (no rubber-coated wheels).

A proper 8 or 12 speed auto trans for a CUT would need a stronger and shorter case. The market is small - so it will be pricey if we ever see it.

 

[wmonroe]

I have been using my brother in laws NH to feed his cows lately since he is feeling poorly. What I noticed with his HST is that it performs poorly at less than about 1800 rpm. It will stall the motor and has very little pulling power at less than 1500 rpm with empty tractor and a bale of hay on the front spike. MY Kubota works even at idle and never actually stalls the engine when using the HST even in H range. I rarely rev the engine on it past idle to back it out of the shed. I can work HST, hydraulics etc at idle and they work good whereas his FEL hardly moves at idle. I guess some HST transmissions just work a bit different. I always wondered why he reved up his engine so much just to ease back when hooking up to a 3 point hitch, now I know.

My Kubota operates like yours, can move it out of the barn and drive at idle. Usually do most loader work at 1500 rpm unless I'm traveling a distance between scoops and want to speed up.

Agreed - I wasn't saying CVT, I said "more continuously variable" which in my mind means more gears with intermediate sliding-ratio planetary sets - like the ZF 8-speed now offered on high-ticket cars. (no rubber-coated wheels). A proper 8 or 12 speed auto trans for a CUT would need a stronger and shorter case. The market is small - so it will be pricey if we ever see it.

My wife has the zf 8 speed in her grand Cherokee and it is a sweet transmission, something like it in a cut would be very interesting.

 

[s219]

I have been using my brother in laws NH to feed his cows lately since he is feeling poorly. What I noticed with his HST is that it performs poorly at less than about 1800 rpm. It will stall the motor and has very little pulling power at less than 1500 rpm with empty tractor and a bale of hay on the front spike. MY Kubota works even at idle and never actually stalls the engine when using the HST even in H range. I rarely rev the engine on it past idle to back it out of the shed. I can work HST, hydraulics etc at idle and they work good whereas his FEL hardly moves at idle. I guess some HST transmissions just work a bit different. I always wondered why he reved up his engine so much just to ease back when hooking up to a 3 point hitch, now I know.

I think it really depends on the power and weight of the tractor.

My old B2920 had a lot of power for a light tractor, and felt much like you describe your Kubota. Did a lot of work just past idle and rarely had to rev up higher except when running a PTO implement or dragging a box blade full of material.

My new L3200 has about the same power as the B2920 but weighs nearly twice as much, and feels about like you're describing your brother in law's NH. I have to get up to 1800-2200 RPM just to drive around comfortably and do work.