Broken HST/ No Reverse= HUGE $ to Fix!

[dfkrug]

Full throttle, brakes locked, oil at operating temp is typical procedure and not just Kubota.

Yeah, seems pretty standard to me, according to all the JD, Kub, and Kioti service manuals I have. Looking
forward to when I have an excuse to run this test....

 

[rbargeron]

Full throttle, brakes locked, oil at operating temp is typical procedure and not just Kubota. You don't need to hold it over relief long, it is either going to make the pressure or not. It is even possible that it will over power the brakes, in which case you'll want to block the tires. Oh, and open the throttle all the way first and ease into the HST pedal. Brian

Good advice - I'd be doing the test with the tractor on the lift. Thanks for your first-hand experience. All indications so far are that the regulator is not producing correct differential pressure across the servo cylinder. The regulator is adjustable but it would be great to know the factory procedure for balancing the system.

 

[brain55]

Good advice - I'd be doing the test with the tractor on the lift. Thanks for your first-hand experience. All indications so far are that the regulator has a problem getting pressure to the bottom of the servo cylinder. The regulator is adjustable but it would be great to know if a special test fixture is needed to get everything right on both ends.

Yeah, the L48 was after my time in the dealership, if it was a little bit older model I'd probably have the manual out in the garage.

 

[brain55]

I just went out to the shed to double check to see if I had the L48 shop manual, I didn't but I do have the L3010-4310 manual which should be the same hydrostat. I can scan this stuff and post it if you like. There is absolutely nothing about testing the servo valve or piston, but the operation of it is pretty detailed.

Brian

I was just going to post these pages but decided 16 pages was too many. I can email them to you if you want to PM me your address.

 

[MHarryE]

I don't know your hydro at all, but the problem reminds me of something not infrequent on hydros I am familiar with. They orifice the flow to the servo piston so the swash plate doesn't tilt too fast - immediate skidding stops, spinning the tires on acceleration. Each side of the piston is orificed separately. Since oil flow to and from the servo is a safety item(think of a blocked orifice when you want to stop - it won't let the oil out so it won't destroke and won't stop, below a certain diameter our supplier uses a shuttle orifice that resists plugging but if it gets a chunk in it, it may not stroke at all or it may become erratic if it is a piece of crud in the shuttle chamber. The fix for your exact symptom is to pull the orifice and clean it but like I said, your hydro may be completely different. Still you have a pump and a motor that uses the same parts going forward and reverse - except for the control. We have a reman program that gives a reman hydro for half the cost of a new one. Looking over some that come back on exchange - the problems range from a blown piston (material defect) to no problem found. American dealers make extensive use of the reman program to avoid fixing things. Third world countries rarely use reman - they do what you are doing - find it and fix it.

 

[Coyote machine]

<Snip> Third world countries* rarely use reman - they do what you are doing - find it and fix it.

So third world*, like us, but wait, nobody here knows how to fix anything anymore, or for that matter MAKE anything anymore....:confused2:

Sorry couldn't resist:confused3:

I do agree that much of what goes out as remans is to save having to fix anything, and in the case of something that comes in to be remanned, BUT isn't broken, then double the money- just send it out as remanned and no costs/labor, but money made nonetheless.

 

[aczlan]

I do agree that much of what goes out as remans is to save having to fix anything, and in the case of something that comes in to be remanned, BUT isn't broken, then double the money- just send it out as remanned and no costs/labor, but money made nonetheless.

Also, your guys might rebuild something 2-3x/year vs a reman shop who does them every day. With a good reman shop, they can also back you up if something goes wrong (ie: you aren't wholly on the hook if it fails 2 days after it leaves your shop).

Aaron Z

 

[SSdoxie]

Looking at Kubota's online parts illustraion for the L48 HST, I see there are 2 pairs of poppets/reliefs. The first picture is of the "Valve Assy High" which should be the high pressure relief with directional check. Item #030 (qty 2).


The next pic shows what Kubota calls "Vlave Assy. Low" (qty 2) Item #110. Not sure what they are but since there are 2, I believe they would be directional related and they are shimable so I think they might be "neutral valves" to give smoother transition in & out of neutral. If 1 of these is stuck or broken spring would give the same loss of drive in one direction.

 

[rbargeron]

I just went out to the shed to double check to see if I had the L48 shop manual, I didn't but I do have the L3010-4310 manual which should be the same hydrostat. I can scan this stuff and post it if you like. There is absolutely nothing about testing the servo valve or piston, but the operation of it is pretty detailed.....I was just going to post these pages but decided 16 pages was too many. I can email them to you if you want to PM me your address.

Sent you my email address - thanks.
The Lxx10 and L48 are pretty similar in many ways. When you look close, it's clear that the L48 is an armor-plated a Lxx10. A lot of the transmission & gear cases (and the HST) are the same - but the L48 has the massive main frame to take the 3pt and BH attachment points. And they put a 2500 lb loader on the same way - a non-removable boom bolted to an external steel reinforcement. If I park the L48 next to my L5450, I can see how they got the same capability (2500 lb loader, 11 ft BH) using a smaller chassis, but adding framework. Makes perfect sense - most homeowners and small farmers don't need the strength and weight of the L5450 (or other L3's). But I really get a kick out of the L3's old-school overdesign.

 

[rbargeron]

So third world*, like us, but wait, nobody here knows how to fix anything anymore, or for that matter MAKE anything anymore....:confused2:.......

Well it's official - I'm a third-worlder. I both fix stuff and the other night I made a part for the toaster. I just can't help myself. BTW, the Accord's sheet metal is restored, ready for paint (to be done by a pro)