L4610 HST which is the pump & which is the motor?

[westflgator]

I am hoping and praying that one of the Kubota mechanics on this forum can help me out. I have been trying to get confirmation from Kubota as to which one is the pump and which one is the motor on a 2001 L4610 HST. I have the diagram that shows where the pump and motor reside within the HST housing, but I can't find any info that tells me which one of these is which. You can see a difference by looking at the top of the pistons, but so far no one can tell me which is the pump and which is the motor. I have talked with 4 Kubota mechanics so far and none of them were able to tell me which is which. I sure don't want to have to break this tractor apart twice, so I'm just trying to make sure we get it back right before we put it together. I'm sure some of you are wondering why we didn't take a pic, unfortunately when we took it apart they slid out of place before we could get a pic. It was a mistake on our part for sure, one of those lessons learned the hard way. Thanks for your help in advance.

 

[100 td]

I'll take a stab in the dark!
Can you match the wear on the splines of the pump shaft to the pump motor? I expect the pump will only turn in one direction so would only have wear on the splines on one side whereas I would expect the motor would have wear on both sides. The motor would only have even wear if it were used in a constant forwards reverse loading situation, so depending on use the reverse wear may be minimal, but with a good torch, and a cleaned shaft and pump (carby cleaner or solvent leaving no residue) you may be able to match the pump shaft spline wear to the pump spline wear.
Also the position of the wear on the splines on each shaft may give you a clue when measured back from the swash plate or similar.
EDIT: I'll take a guess at the pump being on the right.
And of coarse you could put up a poll and go with the general consensus, which of course could be totally wrong!
And of course my guess may be totally wrong, reasons of thought are that the pump is variable angle swash plate so may use special pistons, whereas the motor is fixed angle reversing. (due to the reversing it may have use for different pistons as well, but I think I'll go with the pump having the special ones.) (Lots of assumptions here!)

 

[North Idaho Wolfman]

If I understand it correctly one can not fit on the others shaft.
In other words the pump can only fit on the pump shaft and the motor can only fit on the motor shaft.
Try dry fitting them and see if that's right.

 

[rbargeron]

Pretty sure your left picture is the motor. The attached pictures are from a parts recycler - the tag has part number TA240-58600, the motor for Lxx10 and L48 HST's.

 

[100 td]

Looking good to double my money from 2c to 4c!

 

[coachgeo]

Pretty sure your left picture is the motor. The attached pictures are from a parts recycler - the tag has part number TA240-58600, the motor for Lxx10 and L48 HST's.

smart twist in use of internet search!!! Searching for sale items can help in lots of situations like.....

I need part #xxxx for my kubota. Wonder what all kubota tractors use part number xxx. hmmm"

 

[westflgator]

Thanks for all the replies and suggestions. I will keep you guys posted as to how it turns out. By the way the original problem were bad seals on the propeller shaft, to get to the back seal we had to split the tractor.

 

[westflgator]

Pretty sure your left picture is the motor. The attached pictures are from a parts recycler - the tag has part number TA240-58600, the motor for Lxx10 and L48 HST's.

The reason for the confusion on my part, is that one of the Kubota shops in the area still had a pump that was pulled from a different model Kubota, and it was smooth like the one shown in your pic. But when I searched the internet I also found some that were listed as motors that were smooth as well. This left me wondering if they were not all the same. We plan to work on it today, so I will double check the size and wear on the shafts as mentioned above to see if I can determine which is which. Thanks again for the help and the suggestions, I just want to make sure I get it right the first time if possible.

 

[rbargeron]

I was under the impression that slippers were smooth on both pump and motor - the grooved-face ones in your right picture were new to me.

When I took apart my first automatic transmission I put a wire through part stacks to aid reassembly. Of course if the last guy put it together wrong that method isn't reliable either.

 

[100 td]

Dang! Looks like I could lose my 2c after all!

 

[rbargeron]

Here's another indication that the picture on the left in the original post is the HST motor.

Googling hydrostatic slipper images brings up several examples - some with simple plain-face and some with a labyrinth in the surface like those in the right-hand pic in the original post. This style seems to be growing in use for hydrostatic PUMPS from several manufacturers.

One apparent advantage of the labyrinth is that small scratches from impurities in the oil don't extend across the whole face, so there's less disruption of the boundary layer, and pump performance life is improved. Boundary-layer friction and wear analysis is pretty much a black art, mostly advanced by experimentation and experience. Some manufacturers still use tried and true plain slippers - while many are going to the labyrinth faces for the pumps.

Found no mention of why hydro motors don't seem to have them.

 

[westflgator]

Here's another indication that the picture on the left in the original post is the HST motor.

Googling hydrostatic slipper images brings up several examples - some with simple plain-face and some with a labyrinth in the surface like those in the right-hand pic in the original post. This style seems to be growing in use for hydrostatic PUMPS from several manufacturers.

One apparent advantage of the labyrinth is that small scratches from impurities in the oil don't extend across the whole face, so there's less disruption of the boundary layer, and pump performance life is improved. Boundary-layer friction and wear analysis is pretty much a black art, mostly advanced by experimentation and experience. Some manufacturers still use tried and true plain slippers - while many are going to the labyrinth faces for the pumps.

Found no mention of why hydro motors don't seem to have them.

Turns out you guys were right, the smooth face was the motor, and the one on the right in my pic with the raised face was the pump. Now that I have fixed the original problem, which were the seals leaking around the propeller shaft, I realize that I created much more work than what was necessary. So I am going to post some pics that might save the next guy some work.

What happened when we tried to pull the shaft out it didn't seem to want to move, and not knowing what was holding it we didn't want to force it too much. So we decided to seperate the bell housing from the HST, but it would only go about 4 inches and stop, my shop manual wasn't very clear and I wasn't sure why, so next we sepearated it from the back of the HST (wasn't necessary). Then finally we sepereated it at the back of the transmission and found a gear wedged onto another drive shaft coming from the HST that drives the rear end; it was moving forward about 4inches and hitting the back on the plate on the HST and stopping.

Thanks again for all of the help, the tractor is back together and seems to be working fine with no leaks so far. I'm in hopes that it is fixed. Hopefully the notes in the pics below can be read.











Maybe I should repost this on my original post about the hydraulic leak coming from the propeller shaft seals. The only reason I even had to deal with the issue with the HST pump and motor was because when I bagged up the HST to keep it clean after I had taken the tranny apart, we inadvertantly tilted it and the motor and pump slid out inside the bad we have it wrapped in (should have taken pics, lesson learned).