zd28 trans problem

jptbow

New member
Jul 29, 2010
1
0
0
Pittsfield, Il, us
i have a zd28 that the left wheel will barely move. I've read that there are problems with pumps or something with these. Is there anything that I can check or do to test this or figure out the problem for sure. I've looked and the rods going to the pump are moving the same....the left and the right. the right works correctly but the left hardly has any response at all. Also is there somewhere that I could download a service manual for this for free?
 

Service Dept Vic

Moderator
Staff member
Vendor Member
Feb 15, 2009
2,512
2
38
Southern Alberta Canada
If that service complaint landed in my shop, I'd start by making sure that the brake is free on that side and not hung up.

If the brake pedal cross shaft or adjuster linkage is siezing or has allready siezed it will maintain the brake on the siezed side.

I'd recommend buying a complete set of manuals for that mower, especially if it's new to you. The WSM, an operators manual as well as the Master Parts and Factory Assembly Order Manual.
 
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dusty-t

New member
Feb 17, 2009
975
0
0
Mountforest Ontario
I am not really familiar with the Zd28 but a lot of the zero turns have adjustments on the hydrostat for each side. Most of the zero turns that I look at either the brakes or hydro linkage is out of whack. Mind you I am usually looking at older stuff.:D Dusty
 

KubotaTech

New member

Equipment
None- I get to play with everyone elses stuff
Apr 1, 2010
185
0
0
PA
If the other things are ok, Drain the fluid, and check the strainer in the bottom of the transmission. If there is any metal shavings. You can also cut open the filter and see if there is excessive metal in it. If there is evidence of an HST failure, there are 2 kits available for an HST replacement. One has the 2 right and left side units, and the second has the 2 units and a charge pump assy. Hope you are mechanically inclined, there is a lot of disassembly required. Be sure to also get the add on tank to increase the fluid level so you dont have a repeat failure.
 

davemskinner

New member

Equipment
sold ZD28F, 04 Grnd L4330 /frnt mnt snwblwer L2185, hted/AC cab, 2nd ZD28F
Mar 12, 2011
89
0
0
Pulaski, NY
A little late but it may save someone else some grief. I took apart the LH drive assembly and reground the backing plate. I also lapped the two rotors. Once back together, I used it for one season. Just before the last mowing, it really crapped out on me. It had been getting weaker but just a little.
Well, long story short, I had to replace both drive pump assemblies and purge the charge pump. All is now good. I also added the extra tank to stop the cavitation. I had planned on making my own and did not get around to it so I wish I had just bought it when I rebuilt the pump. :(

So my $1500 ZD turned into a $3700 ZD :mad: :mad: :mad:

Hope this helps anyone who may be doing this job!
 

leibuys

New member

Equipment
RTV900, KX141-1, L3240w/FEL, ZD-28 72" PRO, 2 GL7000, M4700, B8200 w/FEL
Dec 18, 2011
12
0
0
AURORA, OH, United States
A little late but it may save someone else some grief. I took apart the LH drive assembly and reground the backing plate. I also lapped the two rotors. Once back together, I used it for one season. Just before the last mowing, it really crapped out on me. It had been getting weaker but just a little.
Well, long story short, I had to replace both drive pump assemblies and purge the charge pump. All is now good. I also added the extra tank to stop the cavitation. I had planned on making my own and did not get around to it so I wish I had just bought it when I rebuilt the pump. :(

So my $1500 ZD turned into a $3700 ZD :mad: :mad: :mad:

Hope this helps anyone who may be doing this job!
Hi Dave,
How did you know that both drive pumps were bad and not the charge pump. Also, i'm curious to know the cost of the parts and how you found the part numbers. What I am trying to find out is if Kubota is offering a repair kit or do you have to buy all the parts individually? I assume you also had to drop out th entire transaxle to do the job. Do you recall how long it took you? Thanks in advance? A local service department told me that the parts are $500 plus $1000 for installation but the parts pricing seems low to me.
THanks...
 

eserv

Active member

Equipment
BX24, A1000 Kubota Generator
May 27, 2009
1,862
0
36
Hardisty, Alberta
Hi Dave,
How did you know that both drive pumps were bad and not the charge pump. Also, i'm curious to know the cost of the parts and how you found the part numbers. What I am trying to find out is if Kubota is offering a repair kit or do you have to buy all the parts individually? I assume you also had to drop out th entire transaxle to do the job. Do you recall how long it took you? Thanks in advance? A local service department told me that the parts are $500 plus $1000 for installation but the parts pricing seems low to me.
THanks...
if the right side works ok then the charge pump is working. Kits to repair these are $1265 per side in Canada US is usually
cheaper
 

leibuys

New member

Equipment
RTV900, KX141-1, L3240w/FEL, ZD-28 72" PRO, 2 GL7000, M4700, B8200 w/FEL
Dec 18, 2011
12
0
0
AURORA, OH, United States
if the right side works ok then the charge pump is working. Kits to repair these are $1265 per side in Canada US is usually
cheaper
Why would the right side have relation to the charge pump and not the left. Could you clarify? Thanks for your quick answer...

Joe
 

eserv

Active member

Equipment
BX24, A1000 Kubota Generator
May 27, 2009
1,862
0
36
Hardisty, Alberta
Why would the right side have relation to the charge pump and not the left. Could you clarify? Thanks for your quick answer...

Joe
Because there is one charge pump supplying charge to both drive pumps. If the charge pump fails both sides quit driving.
 

davemskinner

New member

Equipment
sold ZD28F, 04 Grnd L4330 /frnt mnt snwblwer L2185, hted/AC cab, 2nd ZD28F
Mar 12, 2011
89
0
0
Pulaski, NY
The drive motors on each side are actually pump/motor pairs in one assembly. The charge pump feeds both drive motors. When the lefthand side of the machine is up (as on the side of a hill) the drive motor cavitates or starves for oil which causes it to rapidly degrade. Once it wears beyond a certain point, the metal circulates through the charge pump into the other side. This means you now need to replace both sides and maybe the charge pump as well. Very costly. I was able to temporarily repair the first pump/motor, but when it went the second time, it blew bad. I replaced both sides and was lucky enough to only have to disassemble and clean the charge pump.

If only one side is weak you may be able to just change the one side. However, You run the risk of destroying both the other side and the charge pump, or worse yet, if the second side fails, your new pump/motor has to be replaced again! My dealer won't replace just one.

There is lots of good info above. We have some great people here on this forum, eserv and Service Department Vic, to name a few!

Good luck and keep us posted!
 
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davemskinner

New member

Equipment
sold ZD28F, 04 Grnd L4330 /frnt mnt snwblwer L2185, hted/AC cab, 2nd ZD28F
Mar 12, 2011
89
0
0
Pulaski, NY
Hi Dave,
How did you know that both drive pumps were bad and not the charge pump. Also, i'm curious to know the cost of the parts and how you found the part numbers. What I am trying to find out is if Kubota is offering a repair kit or do you have to buy all the parts individually? I assume you also had to drop out th entire transaxle to do the job. Do you recall how long it took you? Thanks in advance? A local service department told me that the parts are $500 plus $1000 for installation but the parts pricing seems low to me.
THanks...
How did you know that both drive pumps were bad and not the charge pump. See my previous post (just made).


Also, i'm curious to know the cost of the parts and how you found the part numbers. Messick's (site sponsor) has all the parts manuals right on-line. You just provide an email address and they send you the section you request. It's awesome! They will provide quotes. As eserve said above, you can buy either side, both sides, or both sides and the charge pump. The cost of the kit for both sides together was $2000 + tax.


I assume you also had to drop out th entire transaxle to do the job. Do you recall how long it took you? Thanks in advance? A local service department told me that the parts are $500 plus $1000 for installation but the parts pricing seems low to me. I think I took a weekend to replace the two sides. However I am quite slow when doing mechanics, as I don't do it every day. I did not drop the entire transaxle. I did one side at a time and then opened up the charge pump to clean it out. I think it would be way easier to drop out the entire transaxle. Maybe eserv or Service Department Vic can weigh in here. You are correct about the pricing being low. I would get a detailed understanding before I went ahead with that.
 

ljd

New member

Equipment
ZD28, BX25, landpride rear tiller, brush hog, front snow blade, carry all
Oct 6, 2013
2
0
0
Somerset, Ohio USA
I have a ZD28 Kubota I bought new in 2006, it has 366 hours on it now, I've only used it on my yard and it is mostly hills. The last few times I've mowed with it I noticed the right side drive getting weak. I came to the internet and found this post and freaked out.
I've done all the maintenance on this thing myself and wanted to make it last as long as possible. So, I just drained the Super UDT out and looked at the magnet on the drain plug and saw nothing (no metal) Then I removed the suction banjo and the screen had a bunch of like grey silicon chunks plastered around it. There looked to be about an inch of the grey silicone like stuff, on the screen, if the chunks were lined up about the diameter of spaghetti. The fluid level was about 1/4" above the full mark on the transmission pump. There has never been any leaks and the fluid has never been low on the transmission.
Do I really need to expect to pay out as much as $4500 to fix this thing or should I get a mower deck for my BX25 and spend more time mowing?

Any help on this issue will be appreciated. Is it possible there is something that clogged the passage ways to the right pump and making it not work properly or starved the pump to the point of having to replace it? The mower does still move but it was giving me problems when I took it to the barn. When I bought the ZD 28 I was told by the dealer that "If you want a Zero turn on hillsides it has to be a Kubota".
 

ljd

New member

Equipment
ZD28, BX25, landpride rear tiller, brush hog, front snow blade, carry all
Oct 6, 2013
2
0
0
Somerset, Ohio USA
I have a ZD28 Kubota I bought new in 2006, it has 366 hours on it now, I've only used it on my yard and it is mostly hills. The last few times I've mowed with it I noticed the right side drive getting weak. I came to the internet and found this post and freaked out.
I've done all the maintenance on this thing myself and wanted to make it last as long as possible. So, I just drained the Super UDT out and looked at the magnet on the drain plug and saw nothing (no metal) Then I removed the suction banjo and the screen had a bunch of like grey silicon chunks plastered around it. There looked to be about an inch of the grey silicone like stuff, on the screen, if the chunks were lined up about the diameter of spaghetti. The fluid level was about 1/4" above the full mark on the transmission pump. There has never been any leaks and the fluid has never been low on the transmission.
Do I really need to expect to pay out as much as $4500 to fix this thing or should I get a mower deck for my BX25 and spend more time mowing?

Any help on this issue will be appreciated. Is it possible there is something that clogged the passage ways to the right pump and making it not work properly or starved the pump to the point of having to replace it? The mower does still move but it was giving me problems when I took it to the barn. When I bought the ZD 28 I was told by the dealer that "If you want a Zero turn on hillsides it has to be a Kubota".
UPDATE: I purchased the Kit # K3151-98060 ($1660) and am in the process of putting the transmission back together. The instructions call for a .020mm shim that goes between the bearing and the spiral gear on the input shaft mine is missing. I just wonder if this shim is something that is sometimes not needed unless parts are machined in a bit undersized to get the gears to mesh flush. My gears mesh flush without this shim. Someone who rebuilds Charge Pumps may have some insight. I'm putting it together using Ultra Grey permatex for the gaskets. Also the Rotor has punch marks on one side of each part, anyone know which directions the punch marks go into the charge pump case?

Of course I was curious as to why my problem of the right side pump motor was weak. The service rep I spoke with from Kubota told me these hst units could not be rebuilt. Remember This was a known problem with ZD28 transmissions and I'm out of warranty.
 

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zmega

New member

Equipment
ZD-25 mower, L series tractor
Jun 15, 2017
1
0
0
Leesburg, VA
Apparently this is a common problem. My ZD25 began to fail a while ago (now has about 520 hours). Defective lubrication system design.
 

lugbolt

Well-known member

Equipment
ZG127S-54
Oct 15, 2015
2,220
37
48
Mid, South, USA
It's not a defective lubrication design. It's not a defect at all, really. What is is, is a maintenance problem and a service/owner's manual problem mostly.

The "book" says to change the fluid as x amount of hours. What the book doesn't say is that in hot climates, it needs to be changed more often. Also the cooler and radiator/screens need to be KEPT squeaky clean. So this means you get to change the fluid and filters more often if you live in a climate area that is over 90 degrees or thereabouts (pretty much the entire country). Most don't do it often enough; and it eventually leads to problems from heating the fluid, then the fluid can't remove heat from either HST effectively enough.

When experiencing an HST problem on any of the ZD mowers (21, 25, and 28 mostly-the 18 rarely had HST issues but it was lighter and less powerful), quiz the operator how it gets used, how often the fluid is changed, and what kind of fluid is used. Regular UDT won't cut it in a 21, 25, and 28 HST. Super UDT2 only and nothing else. there was also a hydraulic reservoir that could have been added to the system which increased the fluid capacity, but honestly it's not needed if the fluid is changed often. Also when doing a fluid and filter change, it's always adviseable to pull the screen while you're under it, clean it, and reinstall. Make sure the O-rings are in good condition and in their proper positions.

Another issue is the simple relplacement of a part, in this case an HST on one side only. Where did all the brass and metal shavings go? Through the ENTIRE transmission. Replacing one HST solves the immediate issue but there's still junk left inside the center case, brake cases, and the other HST...oh and the hydraulic system too. Need to get all that stuff out or it's very possible that the other HST may fail too. Need to check/verify charge pump pressure as well, per WSM. I like it on the higher side personally, so that as fluid gets hot, it doesn't drop the psi below spec.

The ZD300 series HST is totally different. Everything is bigger-a LOT bigger. Charge pump is twice the size, holds more fluid, different cooler, etc. But the mower itself got bigger as well and that's what I didn't care for on the ZD300's-it's size. It was like going from a Ranger to a F350 dually. You get used to it but it takes a while.