Kubota M62 Drive Disengages By Itself

[RedNeckGeek]

I've been mowing on steep uneven ground the past few days and have a problem with the tractor coming to a stop all by itself while traveling in a straight line. Engine speed isn't effected; it's as if I've taken my foot off the Speed Control Pedal causing the tractor to stop. I've also seen this behavior when turning the steering wheel near or at full lock while in four wheel drive while moving. It's almost as if there's some kind of safety cutoff that senses the drive line loading up and disabling the drive train to stop the tractor.

Taking my foot off the Speed Control Pedal and pressing back down in the former direction of travel has no effect, the tractor just sits there. Sometimes pushing the Speed Control Pedal for the opposite direction will cause the tractor to move in that direction, and then the original direction starts to work again. Other times travel in both directions is disabled. I've been able to get it going again by turning the steering wheel from side to side. Sometimes I have to turn the engine off and restart to get going again.

This is more than just a PITA, it's also a safety problem when working on steep ground. The tractor doesn't take off like it was in neutral, but it will move downhill unless I hold it back with the brake. That could be real bad news if the Speed Control Pedal or steering wheel manipulation doesn't restore motion.

I've verified that this is not the Operator Presence Control in the seat acting up by taking my weight off the seat while the PTO is running. When I do, the engine dies unless I sit back down immediately. The engine will die when I lift my butt off the seat even when I'm not using the PTO, so I don't think the PTO has anything to do with the problem. And the problem still happens even when the Bushog is replaced with the box blade.

Sorry if my description is unclear; I'm really not sure how to describe what's happening. Maybe there's a ghost in the machine?

Anybody having similar problems on an M62 or other Kubota tractor?

 

[JWR]

Well, you have a long history of experience so I must assume you have checked the hyd fluid, made sure there is plenty of that, looked at (or replaced) the hyd filters so they are not clogged or restrictive, etc. At first blush it would seem like the main HST is gasping for fluid.

I'm guessing you used to use the L3240 for mowing and, when you got rid of it, are converting to using the M62 with bush hog for mowing...

Yeah, I sure agree you cannot stand to have this driveline stoppage going on when operating on steep ground.
Several questions (which may help others to understand your problem & maybe know what is wrong...)

• You are getting no red lights or dash indictors?
• Are the rest of your hydraulics operating OK when this disease hits (like FEL and 3pt lift?)
• Hours on this tractor ? Not real high?
• An M62 is not your typical mowing tractor -- more of a backhoe comfort zone. Did you have hoses and/or control linkages apart getting the backhoe off and the mower/ 3pt hitch hardware on?
• I am ignorant of the M62 controls: Is there a safety or setting control that you are supposed to use when the machine is parked and braced in position for doing backhoe work (to make sure the machine is'nt going anywhere while you are using the backhoe) ?? Is that a manual control or automatically invoked when using the backhoe?

Good luck.

 

[mikester]

Sounds like drive by wire issue, check out my post#11

Kubota L4701 Sometimes Stalls When Moving Forward with HST Pedal

This winter I've been having a problem with the tractor where it starts fine, and then when I press the HST pedal to move forward it stalls. If I leave off the pedal quickly it will not stall and RPMs will come back up. Interestingly, when pressing the pedal for reverse it does not stall. Is...

www.tractorbynet.com

 

[RedNeckGeek]

Thanks for the replies. Good questions; here are some answers:

No red lights or dash indicators.

But I haven't yet checked for trouble codes. I'll do that.

No issues with FEL or 3PH; I've experienced the lurching that low hydraulic fluid can produce and that doesn't seem to be the problem.

Right at 600 hours.

Hydraulic fluid is at the proper level, but the tractor is due for a new HST filter.

Haven't had the backhoe on in more than a year. It uses several dedicated hydraulic ports on the rear of the tractor.

There are two valves on the back each actuated by an odd lever that gets switched between backhoe and 3PH modes. I'll check to make sure they're set properly, but my past experience is that the tractor won't start if they are set wrong.

I searched the Owner's Manual for safety switches and lock outs, and the Operator Presence Switch in the seat is the only thing I found. It works by killing the ignition when weight is removed from the seat, and as mentioned, I tested it to make sure it is working as designed. When the tractor won't move, there is no change in engine RPM. In fact, while mowing, I set the RPMs to about 2200 with the hand throttle, and that RPM is maintained while the Speed Control Pedal has no effect.

One of the posts in the linked article mentions an HST safety switch under the left hand side of the tractor. I'll see if I can locate it. I do recall that the Speed Control Pedal uses mechanical linkage and cables, but that doesn't mean that there isn't a safety switch in there somewhere. Next time I have a chance I'll try digging through the shop manual to see if there is any mention of the HST safety switch.

For now, though, I'm pretty much done with mowing, at least until we get more rain. And I'm hoping we don't. A few years ago it kept raining into June, and I had to mow twice.

 

[RedNeckGeek]

Was out on the tractor again yesterday, and I'm pretty sure the problem is triggered by me shifting my weight around in the seat. I was doing a lot of work with the box blade that involved turning around to look backwards, and pushing on the back of the seat. Several times when twisting around into that position, or twisting back forward, the tractor stopped moving and I had to dance around on the Speed Control Pedal, or turn the steering wheel from side to side, to get moving again. It was pretty repeatable. It does not kill the engine like lifting my weight off the seat does, it just stops the tractor from moving. When I get a chance I'll get the parts diagram for the tractor out and see if there's some kind of sensor in the seat or seat support structure. Maybe there's an adjustment to make it less sensitive.

 

[rbargeron]

Sounds like maybe fluctuating HST charge pressure? The HST charge pump's oil cooler has steering fluid running through it too. Do the cooler and its tubing look ok?