New HST Slipping??

[hill]

I'm not sure if I have a problem but four times when inching the tractor either forward or backward there has been a distinct lurch as I applied pressure to the pedal.

No load on the tractor - simply moving into position to make hookups with the 3PH and to reattach the backhoe in situations where I need the tractor to move just a little bit more either way.

RPM's have been low, both 1200 and about 1800 rpm. Does it at idle too. Tractor in midrange of the B7800 3 range system. It's a familiar feeling for anyone who's had an automatic transmission that needed to be gassed a little before the trans would engage and get you moving. All of a sudden, lurch. In these cases the lurch has been almost too much and nearly caught my wife's fingers one time.

The tractor is nearly new and has very low hours - less than 20. I didn't notice it doing this until we removed the backhoe and found no oil on the dipstick. It only took about 1/2 quart to refill and I guess that's how much is in the lines of the hoe.

I think that the oil info is unrelated but I'm wondering if the weight reduction in removing the BH has only made me experience something that is normal for an unladen Kubota?

....a thought as I write this: Could it be that the HST is shifting to low range without input from me? Do they change RANGES automatically? If it were that I guess it could cause my perception of slipping.

Do I have to call the dealer already? Tell me it ain't so!!

It was against my gut instincts to buy a machine with any sort of automatic transmission. I've never owned one though I spent a year rebuilding them while in college years ago. Don't trust them - Is this supposedly dead reliable Kubota HST going to be my ultimate justification.

 

[vic4news]

I have B3030 and have noticed the same surge. I have expeienced it with the backhoe on or off. I don't think the B21 I used for about 3 weeks had as much jerkiness, but from what I have read here, it sounded normal for HST. I'm also interested in what others have to say about this.

 

[DiezNutz]

You can relax, nothing is wrong with your HST. This is fairly normal. Let me guess... it doesn't lurch when it's cold, only after the hydro fluid has warmed up, and then mostly only the first time you touch the pedal after you've been sitting motionless for a bit. Sound about right?

Not completely accurate to think of your HST as an A/T other than the fact that they both use hydraulics and are complicated. Unlike an A/T, your HST doesn't have a torque converter or dynamically shift between gear sets. The only "gears" are the 3 output ranges that you shift (manually) without a clutch and not while moving. It can not and will not shift them by itself.

It's more like static pressure builds behind the hydraulic motor block until it nudges the motor enough to where the ports line up, then the pressure is released in a surge, giving the motor a twist in the process. It seems to get better with time/usage as things loosen up. You don't notice it as much with the tractor loaded down, because the HST has less leverage against the extra mass. Oil level being a bit low wouldn't affect it since you have close to 4 gallons in the case and the pickup is at the bottom of the sump.

When attaching or removing implements, it's always best to use L range. The wife will appreciate it. HST's have proven to be very reliable (especially when properly maintained)

 

[lawn_king]

Once you get through the break in and perform the 50 hour full service, everything changes. The machine will operate/shift in a much smoother manner and the fuel will go further.

 

[hill]

You can relax, nothing is wrong with your HST. This is fairly normal. Let me guess... it doesn't lurch when it's cold, only after the hydro fluid has warmed up, and then mostly only the first time you touch the pedal after you've been sitting motionless for a bit. Sound about right?

Not completely accurate to think of your HST as an A/T other than the fact that they both use hydraulics and are complicated. Unlike an A/T, your HST doesn't have a torque converter or dynamically shift between gear sets. The only "gears" are the 3 output ranges that you shift (manually) without a clutch and not while moving. It can not and will not shift them by itself.

It's more like static pressure builds behind the hydraulic motor block until it nudges the motor enough to where the ports line up, then the pressure is released in a surge, giving the motor a twist in the process. It seems to get better with time/usage as things loosen up. You don't notice it as much with the tractor loaded down, because the HST has less leverage against the extra mass. Oil level being a bit low wouldn't affect it since you have close to 4 gallons in the case and the pickup is at the bottom of the sump.

When attaching or removing implements, it's always best to use L range. The wife will appreciate it. HST's have proven to be very reliable (especially when properly maintained)

No, actually it is doing the lurch cold. I haven't used the tractor enough to get it warmed up in the last few days and I can't say whether it will continue to have the syptom when warmed by running a while.

While it's encouraging to hear from others that time will make it better you'll have to admit that the same sort of assurances are commonly used by vendors to keep complaining customers at bay long enough for a warranty to expire

I have a gauge on the way and will need to figure out what adapters are needed to tap into this tractor's hydraulics at various places. The repair manual is perhaps the most ambiguous publication I've ever seen and it makes it difficult to determine whether HST internal pressures are the same 1920 -1990 psi range of the operating system. I'm sure I'll want to set them all high side wherever I can.

Good to have affirmed that the HST will not change ranges for me. I thought it would not but threw it out here as a consideration in case I was wrong.

I go around mumbling that I should have bought a Jinma. I'm a fiddler by nature and for better or worse those Chinese tractors seem to be made for the type of person who likes to mess around with stuff. besides, I just read that they come with 16 forward gears! 16!!! To me that's nearly an unimaginable luxury! I'm threatening to go get one anyway and leave the Kubota to my wife for her pleasures.

 

[DiezNutz]

While it's encouraging to hear from others that time will make it better you'll have to admit that the same sort of assurances are commonly used by vendors to keep complaining customers at bay long enough for a warranty to expire
LOL, good point. Naturally I meant nothing duplicitous.

I have a gauge on the way and will need to figure out what adapters are needed to tap into this tractor's hydraulics at various places. The repair manual is perhaps the most ambiguous publication I've ever seen and it makes it difficult to determine whether HST internal pressures are the same 1920 -1990 psi range of the operating system. I'm sure I'll want to set them all high side wherever I can.
Are you sure you really want to go poking around in a very new very expensive HST? I mean, if you really think there's a problem, why not call your dealer? Btw the HST internal pressure is not constant... I believe there is a procedure in the WSM for checking it at different conditions.

<snip>

I'm a fiddler by nature and for better or worse those Chinese tractors seem to be made for the type of person who likes to mess around with stuff.
I like to fiddle with stuff too, but not have to when I need to be productive with it. You have to ask yourself how you'd rather spend your "tractor time".

 

[hill]

Oh, I'd be certain to keep the Kubota for working and a Jimko, err, Jinma for when I yearn for something more to fiddle with. More than the little 12 acres here, more than my current crop of three old Toyota land cruisers in various states of restoration, more than my equipped shop with lathe, mill, shaper, three welders, and even a surface grinder, and more than my pretty well developed ability to build up sub minute of angle rifles and finish their surfaces in steel, fine wood, or even fiberglass.

For someone who was so proud of himself in achieving the facility to retire completely debt free and set up for a life of liesure and travel at age 47 I sure do spend a lot of time working, a heck of a lot more now than I did before retiring. but I'm to enjoy it now, of course, and I think of that when dressing my cuts or exercizing away the assorted strains that result from lifting and working with so many things that are plain heavy. How I feel my age now, I mean FEEL it, when screwing around with things that hook to 3PH'es (WHAT an infernal invention THAT is!, but that's yet another topic).

How naive was I when I loudly declared at age 27 that I would never again turn a wrench At least I don't have to shave anymore, or even shower each morning. I have no need to be presentable anymore and perhaps that sums up the benefits of my retirement from work, if not yet from the world.

Still, I doubt I'll resist for long the temptation to max up the pressures in the Kubota systems. Within specs, for now and the life of the warranty. I am sure that I can do that without leaving a detectable trace of my having done it.

 

[wushaw]

Surging when trying to move just a little is normal, Also depending upon what range you have selected will determine how much of a surge you will get.
Try it you will see what I am talking about.
Shift into low when hooking up to your implements to make it smoother. I wouldn't use high range...you could damage your wifes finger for sure.

 

[texasjohn]

I always use low range when hooking stuff up, never high or medium... no surges that I have ever experienced. I also use idle speed when hooking up.

I had the dealer check (just below minimum spec) and increase my hydraulic pressure (to just over max spec) and it made a very significant difference in FEL lifting capability.

LOL... re your aching and bleeding retirement... congratulations! Me too!

 

[rural2]

I ALWAYS USE LOW GEAR on a B7800 when someone is helping hook up back there. Waaaayyyy dangerous otherwise! Unlike mid and high, I have never had a surge in low (that I recall anyway). Bad news, if you want to look at it that way, is the surge won't get better with use (mine hasn't). SUDT fluid may help??? Never bothered to try it since it is a non issue for me. Just throw the lever, big deal!
Almost anything is better than a pick, shovel and wheelbarrow, however having operated both manual and auto transed CUT's, I'll pick the auto every time given a choice. That last statement goes double if I am doing loader work.
Oh yeah, early retardedment here too, if you want to call it that... Sometimes I think I might go get a job just to get some rest...