Jerky B7500HST

[sunfun26]

I've had this tractor for 10 months now and it has always jerked, 1-2 inches, when starting off. Forward, reverse, hi range, low range. At 88 hrs its almost gone in low range, but is still annoying in high range. It also poses a safety issue, you know, fingers in hitches. My Kubota dealer hints this is normal on all hst's, a design flaw and suggest I shift to low range when injury or damage is a factor. The dealer also checked the closing pressures of the neutral valves at Kubota's instruction at the 50 hr service and they checked ok. /forums/images/graemlins/mad.gif
Anybody else had this problem? /forums/images/graemlins/confused.gif

I've paged back through 50 pages of post and can't find anyother similar problems listed.

 

[Henro]

I don't notice that on either of mine...bx2200 and B2910.

It should be smooth. Very smooth...at least that is my experience with mine.

Try a different one at the dealers. a B7500 like yours or some other size. If it is different and smooth, tell the dealer to fix it or take it to another dealer. That is what I would do...

I did try a B7500 when I was shopping two summers ago and it was no different that what I have now.

Take advantage of your warrenty while you still have it ...

Sounds funny that the dealer would not recognize that something is not right.. /forums/images/graemlins/confused.gif /forums/images/graemlins/confused.gif /forums/images/graemlins/confused.gif

 

[NIXON]

Sunfun ,
I don't own a 7500, But my Hst doesn't do what you describe . It's very progressive and smooth forward or reverse . I honestly wish I had an answer to your problem .
Have you thought of talking to another dealer , or the local Kubota rep ? John

 

[skycopatc]

I have a B7500 with 30 hours and no problem like that.

 

[art]

You aren't by any chance using the clutch petal are you?

 

[TractorAddict]

Just curious as to how high you are running your engine RPM's when you notice the problem. I have a new B7500HST with 83 hours. The only time I have experienced anything like you describe is if I have it running up over 2500rpm and bump the pedal a little hard by accident. Does it do it reguardless of engine rpm? Does the fluid level check out ok? Does it get better or worse as the transmission warms up? Or does it stay the same?

 

[8561]

I've noticed something somewhat similar on my B2410. It was new this year and hs about 70 hours on it. Mine doesn't jerk from a start at all, however sometimes when it's under load, like pushing a blade or going up or down a steep hill, it will be rolling along and then sometimes surge a little and pick up speed. This is with the HST pedal fully depressed and I normally run in the 1800-2300 rpm range. I've only noticed it in low range since that it what I mostly use, and am using while the engine is under load. I have done the full 50 hour service which didn't affect it. Maybe I should call the dealer. /forums/images/graemlins/confused.gif

 

[sunfun26]

No engine rpm doesn' seem to be a factor. The jerk is there atlow and high rpm, hot or cold.
Its almost like play in the drive line only on the hyd side. You can hear the jerk in the hyd wine. I can also feel it while traveling on hills. Coasting, somewhat, down and then a small jerk as the play is taken up on the up side. This is tolerable, its the initial jerk when starting off with the hydrostat peddle that bothers me.

Thanks for all the help. I'm looking forward to hear what Kubota tech support says this time.

 

[kubmech]

Yes it is normal for alot of Kubota HST's. One trick that seems to improve this situation is remove the neutral valves and disassemble the valves (remove roll pin, valve comes apart) Cut one ring from the tension spring and re-assemble. The jerking you describe is caused by the neutral valves holding on to neutral bypass a little longer than they should. Why do some do it and others don't? Just a combination of different tolerences in the valve as well as the HST assembly. I'ts about 60-40% accross the board on the ones that do it and the ones that don't, 60% don't. I'ts not something that will cause damage to the trans but some guys do find it annoying.

 

[Henro]

Kubmech,

Haven't heard your voice for a while...good seein' ya here again. /forums/images/graemlins/smile.gif

 

[8561]

Thanks kubmech. I think sunfun and I are having the same problem, it's just showing up or being described a little differently. Glad to hear its nothing major. I didn't feel like it was but I wasn't sure. Appreciate your knowledge very much!

 

[chim]

8561, my B7500HST does the same as your tractor. There was a post about this quite long ago. I forget who posted it, but they said it is perfectly normal. The explanation of what was happening was clear - I simply can't remember what it was /forums/images/graemlins/blush.gif

Regarding the jerking, the Kubota is smooth. It can be moved very slowly on the first move after startup. SSince it is garage-kept, it is usually driven outside slowly soon after it starts (garage is attached to house @ family room - diesel smoke isn't appreciated by all parties). I have a Ford 1210HST that has jerked ever since I bought it (used) about 10 years ago. The first teensy bit of travel it does after a cold start is a short lurch. It doesn't seem to make any difference how long I allow it to warm up. When it comes time to move it, I can gently press the hydro pedal more and more until it lurches forward or backward. After the initial lurch, it will go all day without doing it again.............chim

 

[8561]

Thanks Chim - I'll do a search and see what I can come up with. If I can find it, I'll post the link for anyone else interested.