ZD28F HST Pump Question - Please help

davemskinner

Member
Lifetime Member

Equipment
Sold ZD28F, Bought04 Grnd L4330 /frnt mnt snwblwer L2185, hted/AC cab, 2nd ZD28F
Mar 12, 2011
96
1
6
Pulaski, NY
Hi everybody,
last week I bought a 2004 ZD28 with 1100 operating hours, in Germany. It has almost no power on the right wheel. I think it's the HST issue, described in this thread. I would like to learn more about your approach @davemskinner. Unfortunately, the pictures are not available anymore. Could you reupload them, please?
Greetings!,
I will look for the pics but this was posted a long time ago. I'm not sure I have them.
Also, you should be aware the the repair did not last. I mowed 4 acres and the unit failed after about 8-10 mowings.
What was worse, was the failed pump sent filings throughout the system. I then had to replace both pumps/motors and completely flush out the charge pump.
My recommendation is to replace the bad pump ASAP before it blows apart AND thoroughly flush the system.

Update 8/11/22: I have searched all locations and cannot find the pics. So sorry. I will keep looking though and post if I find them.
 
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lugbolt

Well-known member

Equipment
ZG127S-54
Oct 15, 2015
4,558
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Of course standard procedure is to replace the unit, very few dealers will work on a hydrostatic unit, guess they are afraid they will let the magic out!.

No. The two techs that worked under me were both well versed in HST's. The problems lie in labor and liability, vs the cost of new and any improvements to a new one.

In other words if I removed a HST, pulled it apart, pay a machine shop to lap, machine, then we reassemble--mind you we'd have to pay a shop to do this because we don't have machine shop tooling (this adds cost to the repair) + labor involved in a full teardown, rebuild, sublet costs, we are pretty close to what a new HST unit costs-and it's still the old HST unit. Since the shop has a guarantee on their work (which we stuck to closely), should the repair have an internal problem within the guarantee's timeframe, which might be out of our control (machining, owner related, etc) now we (or the tech) has to pull the entire hst back apart, find/fix the problem which might entail needing expensive parts, any profit that might have been made on the front end is GONE, and the shop loses money-and probably that customer. Not to mention that the 6-10 hours of all-inclusive labor also takes time away from other customers which also costs. Oftentimes taking that into consideration we would advise the customer as such, and if the part number was superceded it could mean that there was an improvment (which the old ZD28 HST's, the replacement parts are most definitely improved). With all that considered it was often a much better option to replace rather than rebuild.

Yeah I know people are gonna go nuts when I said that any profit that might have been made on the front end might be eat up...I guess folks don't understand that a business MUST turn a profit to survive, like there is something wrong with that. And if you work at all flat rate you're going to lose money in the big picture, unless Kubota has changed their flat rate schedules in the last 2 or so years. The other arguement there is "shoulda fixed it right the first time"-and that's valid, but there is always things that happen that are outside "our" control, e.g, maybe the operator run it out of fluid then added it back in, or maybe a replaced part was defective (kubota will warranty a part for 90 days, but they often don't pay the labor to put that replacement part in--gotta jump through hoops to get that-which takes time, of which customers don't want to understand sometimes) or maybe the machine shop left machining debris, which the fault then is shared between the repair shop and the machine shop and good luck getting the machine shop to eat any of it after it's been used, or maybe the operator put 250 hours on it in 30 days. Been through all of those scenarios. One of my biggest beefs with that dealer I worked at was that they had nothing that stated what their guarantee is or how long it was good for. People are smart. They read the "90 day guarantee" and it don't state what is covers, so some dude brings a lawn mower in for an oil change, then 2 months later it starts running like poo with a fouled spark plug. Bring it back and tech's gotta spend a half an hour diagnosing why it's running on one lung to find a spark plug was fouled, then the SW or SM has to call the guy and say look this had nothing to do with what ya had it in for, you owe us 0.5 hr labor + spark plug. Guess what? Customer goes berserk! Normal occurrance....so yes, that guarantee should be in writing what it guarantees and what it doesn't. Or like the one guy, brought his mowers into shop in Feb of every year, for servicing. And we did a LOT of them! Then he shows up 88 days later with a spindle bearing gone. And it's got 700 hours more on it than it did when servicing was done (commercial cutters) but hey--guarantee didn't say it didn't cover that so you owe me a spindle assembly.

If one is doing it themselves at the house and not having to pay labor and all that, by all means go for it. It may happen again down the line because the newer improved part(s) are not installed but that's not really an issue for most DIY'ers as they want it fixed as inexpensively as possible such that it gives some acceptable lifespan after the repairs are made. I'm guilty...and I'm not saying there's anything wrong with that, it's just the way it is.

that's kind of what every single tech job is, considering the cost to repair vs replace, consider the overall condition of the unit, do ya think they're gonna spend a lot of money on it? Does it look like they care about it? Is this repair going to be questionable in nature down the line? Am I gonna have to do it again later on, or something related to it, for free? Is the repair job going to make a little money for the dealer/shop, or is it going to end up biting you in the backside? If you're a good tech you know what I'm talking about here. It's not just fixing a problem, it's a whole lot more complicated. And it's gotten more complicated in the last few years.
 
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Nicksacco

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Kubota L35 TLB
Sep 15, 2021
461
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43
Bahama, NC
Lug, that's a good explanation of the business model, my friend. And it adds clarity I think to DIY v paying to fix v replacement.
If you wanna tinker, go right ahead. It's a great learning tool.
Sometimes I rebuild or fix just for the fun of it as a challenge - but I'm retired and don't necessarily have a timeline to adhere to!
Ain't no way to run a business though!
 
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GreensvilleJay

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BX23-S,57 A-C D-14,58 A-C D-14, 57 A-C D-14,tiller,cults,Millcreek 25G spreader,
Apr 2, 2019
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Greensville,Ontario,Canada
One reason for a shop to replace instead of fixing an HST, is 'testing'. It's unlikely the shop has a 'test jig' that they can test an HST in, same as a car garage not being able to slap the automatic tranny they just tore down to see IF it's works BEFORE reinstalling into the customer's car.

I'm wondering if any shops, especially busy ones, have a dedicated person rebuilding injector pumps ? I can see the need for 1,000s of $$ of equipment and tools and SPACE . While smaller than HSTs, still complicated and 'fininky', better to order one in ??
 
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davemskinner

Member
Lifetime Member

Equipment
Sold ZD28F, Bought04 Grnd L4330 /frnt mnt snwblwer L2185, hted/AC cab, 2nd ZD28F
Mar 12, 2011
96
1
6
Pulaski, NY
No. The two techs that worked under me were both well versed in HST's. The problems lie in labor and liability, vs the cost of new and any improvements to a new one.

In other words if I removed a HST, pulled it apart, pay a machine shop to lap, machine, then we reassemble--mind you we'd have to pay a shop to do this because we don't have machine shop tooling (this adds cost to the repair) + labor involved in a full teardown, rebuild, sublet costs, we are pretty close to what a new HST unit costs-and it's still the old HST unit. Since the shop has a guarantee on their work (which we stuck to closely), should the repair have an internal problem within the guarantee's timeframe, which might be out of our control (machining, owner related, etc) now we (or the tech) has to pull the entire hst back apart, find/fix the problem which might entail needing expensive parts, any profit that might have been made on the front end is GONE, and the shop loses money-and probably that customer. Not to mention that the 6-10 hours of all-inclusive labor also takes time away from other customers which also costs. Oftentimes taking that into consideration we would advise the customer as such, and if the part number was superceded it could mean that there was an improvment (which the old ZD28 HST's, the replacement parts are most definitely improved). With all that considered it was often a much better option to replace rather than rebuild.

Yeah I know people are gonna go nuts when I said that any profit that might have been made on the front end might be eat up...I guess folks don't understand that a business MUST turn a profit to survive, like there is something wrong with that. And if you work at all flat rate you're going to lose money in the big picture, unless Kubota has changed their flat rate schedules in the last 2 or so years. The other arguement there is "shoulda fixed it right the first time"-and that's valid, but there is always things that happen that are outside "our" control, e.g, maybe the operator run it out of fluid then added it back in, or maybe a replaced part was defective (kubota will warranty a part for 90 days, but they often don't pay the labor to put that replacement part in--gotta jump through hoops to get that-which takes time, of which customers don't want to understand sometimes) or maybe the machine shop left machining debris, which the fault then is shared between the repair shop and the machine shop and good luck getting the machine shop to eat any of it after it's been used, or maybe the operator put 250 hours on it in 30 days. Been through all of those scenarios. One of my biggest beefs with that dealer I worked at was that they had nothing that stated what their guarantee is or how long it was good for. People are smart. They read the "90 day guarantee" and it don't state what is covers, so some dude brings a lawn mower in for an oil change, then 2 months later it starts running like poo with a fouled spark plug. Bring it back and tech's gotta spend a half an hour diagnosing why it's running on one lung to find a spark plug was fouled, then the SW or SM has to call the guy and say look this had nothing to do with what ya had it in for, you owe us 0.5 hr labor + spark plug. Guess what? Customer goes berserk! Normal occurrance....so yes, that guarantee should be in writing what it guarantees and what it doesn't. Or like the one guy, brought his mowers into shop in Feb of every year, for servicing. And we did a LOT of them! Then he shows up 88 days later with a spindle bearing gone. And it's got 700 hours more on it than it did when servicing was done (commercial cutters) but hey--guarantee didn't say it didn't cover that so you owe me a spindle assembly.

If one is doing it themselves at the house and not having to pay labor and all that, by all means go for it. It may happen again down the line because the newer improved part(s) are not installed but that's not really an issue for most DIY'ers as they want it fixed as inexpensively as possible such that it gives some acceptable lifespan after the repairs are made. I'm guilty...and I'm not saying there's anything wrong with that, it's just the way it is.

that's kind of what every single tech job is, considering the cost to repair vs replace, consider the overall condition of the unit, do ya think they're gonna spend a lot of money on it? Does it look like they care about it? Is this repair going to be questionable in nature down the line? Am I gonna have to do it again later on, or something related to it, for free? Is the repair job going to make a little money for the dealer/shop, or is it going to end up biting you in the backside? If you're a good tech you know what I'm talking about here. It's not just fixing a problem, it's a whole lot more complicated. And it's gotten more complicated in the last few years.
Ed, nice job explaining this to the forum. There really is no free lunch!
 
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