F3560 and F3690(F3680) Rear Steer Axle – Oil Seal Orientation Issue

[Whit]

I have a F3560 and F3690 both secondhand and new to me recently. I jacked up the rear of the F3560 and oil gushed out from the top axle case. See pic.

I’ve been investigating the rear steer axle seals on my Kubota F3560 and F3690(F3680) as they share pretty much the same parts and have the same issue, worse on the back right. The seal part number 67910-56840 (diagram reference 080). It appears that Kubota installs these seals with the cavity and spring side facing outward (toward air/dirt) rather than the cavity and spring inward toward the oil/lubrication. This can sort of be seen in the service manual. see pic, the springs face the pivot. This goes against the standard oil seal installation practice, which is to have the spring side facing the oil to maintain proper sealing pressure.

The Problem:

• • The top and bottom seals have part 060 in the digram going between them, the part is a metal bushing that allows the shaft to pass through.
  • The seal lips and cavity get dirt packed into them, they wear grooves into part 060over time. The spring corridors and fails. See pic.
  • Once this happens, oil starts leaking from the top axle case since the seal can no longer maintain a tight seal.
  • Replacing all these components adds up in cost, making this a frustrating and potentially avoidable issue?

Design Flaw?

• • Arai, the manufacturer of these seals (ARS SDD type), states that the spring side should face the oil/lubricant side to prevent oil leakage. Seal direction diagram
  • However, Kubota installs them with the spring outward, which leaves the spring cavity vulnerable to dirt buildup. This leads to seal and spring corrosion, failure, and eventually oil leaks. See pics of dirt in cavity.
  • Why did Kubota design it this way? Was this an intentional choice to act as a dust seal, or is this a design flaw that could have been avoided?

Possible Fix:

• • Installing the seals spring-side inward (toward the oil) might improve longevity and prevent premature wear on part 060?

Has anyone else dealt with this issue? Would reversing the seal orientation improve longevity, or would it cause other unintended issues? Let me know your thoughts! I am about to order new seals and metal bushings and I would hate to do this in 12 months time again.

Also the plastic bushings part number 67910-56430 on top of the rear gear case where the steering linkage pivots was completely worn and in small pieces in the grease. I replaced one of these and it seems to tighten up the steering pivot. I need to replace the rest. How often do these plastic bushings need replacing?

 

[GreensvilleJay]

hmm, I don't have your machine or work on them, but agree with the seal maker and 'common wisdom', to install them the other way round. You've already seen what happens Kubota's way.
Yet a 3rd variation is to have the top (inner) seal installed 'wrong' ( Kubota's way) and the bottom (lower) one the 'correct' way ( as the manufacturer of the seal says ).
hopefully someone who'se seen this before will reply soon.

curious.. have you seen any WEAR( light grooving, scoring) where the seals contact the shaft ? If so ,maybe run 1000 grit sandpaper to polish/burnish the shaft ??

 

[MOOTS]

I ran into the same problem on a 3690 at work. Chalked it up to they had been changed before and the person doing it didn’t know what they were doing. I installed them “correctly” as a seal should be and they didn’t leak. Mowers went to auction a few years after.

 

[Whit]

hmm, I don't have your machine or work on them, but agree with the seal maker and 'common wisdom', to install them the other way round. You've already seen what happens Kubota's way.
Yet a 3rd variation is to have the top (inner) seal installed 'wrong' ( Kubota's way) and the bottom (lower) one the 'correct' way ( as the manufacturer of the seal says ).
hopefully someone who'se seen this before will reply soon.

curious.. have you seen any WEAR( light grooving, scoring) where the seals contact the shaft ? If so ,maybe run 1000 grit sandpaper to polish/burnish the shaft ??

Yes not sure if you seen the picture of the metal bushing that goes between the top and bottom seal that allows the shaft to go from the top to the bottom, and that has deep wear groves in it.

 

[Whit]

I ran into the same problem on a 3690 at work. Chalked it up to they had been changed before and the person doing it didn’t know what they were doing. I installed them “correctly” as a seal should be and they didn’t leak. Mowers went to auction a few years after.
View attachment 150258

This looks the exact same as mine with all the dirt in the cavity where the spring is!! That is good to know that you reversed the seal with the spring facing the oil and you had no issues! It seems as having the spring facing out is Kubotas method however if this is the case it should be listed as a wear item in the manual!

I asked a mechanic friend about it and he said as we all know spring towards the oil, and the only reason he could think of to do it spring out was to use the better oil sealing side to keep the dirt out of the case as the oil is not under pressure, but as we know this also leads to issues

 

[Whit]

This type of seal on the steering axle seems common among lots of Kubotas. I found a video of seen replacement on a different machine but the parts are pretty much the same.
Video here