First Kubota repair in 14 years

[orezok]

My 2004 Kubota B7800 finally is facing it's first repair in 14 yers of use. Today a rear axle seal blew out while I was grading at my house. I caught it quickly and lost less than a half gallon of fluid until I could get it to a place where I can repair it. I used to own and operate a transmission repair shop in the late 80's and I have a full shop manual for the 7800, so I think I can fix this on my own.

The manual is vague on replacing the seal and it looks like I have to remove the transmission side case to get the axle out so that the new seal can be installed. What I don't know is if there are any special tools required to remove/reinstall the axle. Has anyone performed this seal replacement that could offer advice?

 

[3Lfarms]

It looks like you should be able to just drive that seal back into place. I would be more concerned with why it came out. I don’t see any reason why it would come out on it’s own. I would first check to make sure the vent isn’t plugged up allowing pressure to build up. Then drive the seal back in and see how it goes.

 

[orezok]

It looks like you should be able to just drive that seal back into place. I would be more concerned with why it came out. I don稚 see any reason why it would come out on it's own. I would first check to make sure the vent isn稚 plugged up allowing pressure to build up. Then drive the seal back in and see how it goes.

I already did that so that I could move it into the shop. It went back in very easy, so I suspect that the seal is possibly undersize. I finally found the part of the shop manual that covers the replacement. The organization of the manual is poor. Looks like remove about 10 bolts and pull off the right side rear axle case for access to the axle snap ring. Parts manual does not show a gasket. I wonder what Kubota uses for sealant?

 

[TMGT]

I already did that so that I could move it into the shop. It went back in very easy, so I suspect that the seal is possibly undersize. I finally found the part of the shop manual that covers the replacement. The organization of the manual is poor. Looks like remove about 10 bolts and pull off the right side rear axle case for access to the axle snap ring. Parts manual does not show a gasket. I wonder what Kubota uses for sealant?

View attachment 575805

If the part doesn't use a gasket it gets a sealant, I prefer one of the Japanese auto manufacturer sealants like Hondabond or the Nissan and Toyota variants. I dont like the off the shelf silicone/rtv stuff you find in the auto parts stores, they dont seem to work as well on the well fitting machined surfaces.
I'm sure kubota sells its own sealant also.

 

[DK35vince]

I changed the same seal on my tractor last year and used Permatex gray maximum torque sealant on the axle housing.
Worked great.
Permatex Ultra Grey Maximum Torque Rigid RTV Silicone Gasket Maker 3.5oz 82194 | eBay

 

[nyone]

I would expect to find a vent possibly not venting if it blew out like that.

 

[gimmodog]

I would not think Kubota would put in a undersized seal

 

[Zebrafive]

Curious, how many hours?

 

[wagne223]

The seal is not undersized. Rubber degrades over time losing its elasticity.
Then it hardens. So a seal that fits tight when new will eventually no longer hold itself in the seat.

It is a mechanical double edge sword.
Rubber is currently the best metal to metal flexible seal, but, oil rots rubber.

Every rubber part on an engine will fail at some point.

 

[orezok]

OP here to answer a couple of questions. The tractor sits outside in the Mojave sun and heat. It has about 600 hours and all of the original hoses are still intact. The vent is open, so no pressure build up.

I seriously doubt that the seal used real rubber. Most likely a petroleum resistant synthetic.

I pushed the seal back in by hand while they usually have to be driven in. Either the seal was undersize (or shrank) or the housing is oversized.

I made a temporary fix so that I could keep using the tractor until I made a permanent repair.

After some research, I decided to use Threebond sealant on the case. It’s used to seal motorcycle cases subject to repeated vacuum/pressure pulses in a 2 stroke and by numerous auto manufacturers for no gasket parts.