M6800 shuttle

[Barker806]

Hello, I am fixing an M6800 and it has the hydraulic shuttle. When I ripped the engine off the bell housing was full of oil. I see it has an input shaft seal on the reverser. Should that be dry and that was a bad input shaft seal? Again I know nothing about the machine.. I did see some sealant on the starter but no o-ring. I would think it would be a sealed starter if it wanted oil in the bellhousing. Also I can't feel any oil pickup and no dipstick but it has a drain plug. I am going to see if I can find. A shop manual for it but didn't know if someone knew what the deal is with this.

Thank you to anyone that is wiser than me on this !

Thanks

 

[Chewwy]

From a google search

“oil in bell housing of kubota hydraulic shuttle system.”

Suggest you purchase a service manual or your machine.
_______________

The presence of oil in the bell housing of a Kubota hydraulic shuttle system indicates a leak from either the transmission input shaft seal, the hydraulic pump seal, or the front axle driveshaft seals.

A small weep hole in the bell housing is designed to drain moisture, but if oil is consistently dripping from it, a seal has failed.
This is a serious issue because hydraulic or transmission oil can contaminate the clutch, leading to premature clutch failure.
Common leak sources
1. Input shaft seal

• Cause: A damaged or worn seal on the input shaft of the transmission can allow hydraulic fluid to leak into the bell housing.
• Identification: The oil will be coming from the front of the transmission, between the transmission case and the bell housing.

2. Hydraulic pump seal

• Cause: Many Kubota shuttle shift systems use a hydraulic pump that is mounted to or goes through the transmission case. A failing seal on this pump can leak into the bell housing.
• Identification: If the leak appears to be coming from the area where the pump mounts to the transmission, it is likely the pump seal.

3. Front axle driveshaft seals

• Cause: On 4WD models, the front axle driveshaft often passes through the bell housing. The seals around this shaft can fail, allowing oil to leak into the housing.
• Identification: This is a common issue on some models. Oil dripping from the bell housing drain hole is a classic symptom of this seal failure.

4. Main seal (engine oil)

• Cause: Though less common for a hydraulic shuttle system, an engine rear main seal leak would also deposit engine oil into the bell housing.
• Identification: To differentiate, engine oil has a distinct smell and is typically a darker, more viscous consistency than hydraulic fluid. It's best to confirm the type of fluid by smell or color.

How to fix the leak
Repairing the leak typically requires splitting the tractor in two—separating the engine from the transmission. This is a complex, labor-intensive job that is often best left to an experienced mechanic.
Steps involved:

1. Confirm the fluid type: Check the dipsticks for both engine oil and hydraulic/transmission fluid to see which level is dropping. You can also dab a clean cloth on the leaking fluid to identify its color and consistency.
2. Disassemble the tractor: The engine and transmission must be separated to access the seals in the bell housing.
3. Identify the specific seal: Visually inspect the input shaft, hydraulic pump shaft, and front axle driveshaft (if applicable) for the source of the leak.
4. Replace the seal(s): Remove and replace the faulty seal. If you have the tractor split, it is wise to replace all relevant seals and check bearings as a preventative measure.
5. Reassemble: Carefully reassemble the tractor, ensuring all parts are properly aligned and sealed. Use a torque wrench to tighten bolts to manufacturer specifications.
6. Test for leaks: Refill the hydraulic system and run the tractor to ensure the leak is repaired.

 

[Too many Kubotas]

That drain plug is there in case the tractor has been sitting outside and water got in there.

Don't ask me how water would get in, but I remember reading that in the manual.

 

[Harry in Ky]

Hello, I am fixing an M6800 and it has the hydraulic shuttle. When I ripped the engine off the bell housing was full of oil. I see it has an input shaft seal on the reverser. Should that be dry and that was a bad input shaft seal? Again I know nothing about the machine.. I did see some sealant on the starter but no o-ring. I would think it would be a sealed starter if it wanted oil in the bellhousing. Also I can't feel any oil pickup and no dipstick but it has a drain plug. I am going to see if I can find. A shop manual for it but didn't know if someone knew what the deal is with this.

Thank you to anyone that is wiser than me on this !

Thanks

I think we can assume the housing and the seal area in particular should be dry. I think it would be a good idea to replace the seal as it appears to be pretty straight forward. Many Kubota tractor models have the driveshaft for the front axle on the bottom of the clutch housing as well, and some have been known to develop oil leaks from that. The parts diagrams don't show that shaft on the clutch housing page so maybe that's not a concern in this case.

 

[ptsg]

That drain plug is there in case the tractor has been sitting outside and water got in there.

Don't ask me how water would get in, but I remember reading that in the manual.

From condensation on the bellhousing area for hot and cold cycles. Some tractors may have a plug, but most have a small hole with a cotter pin just dangling there to prevent the hole from clogging with dust.

 

[Barker806]

Thank you for the tidbits of info! The cotter pin in the bell housing I have seen many times. This tractor is interesting and totally a Japan machine. It's construction is nothing like the tractors I have worked on in the past (massey, Deere and IH). I will get an input shaft seal and replace it because that is simple enough too do. Not a big fan of the V3300 balanced engine. This one wiped out all the gears when it welded a counterbalance shaft to one of the bearings! This tractor is way more complex than it needs to be. But we have finished a rebuild of the engine and now it's time to find the "other" issues. The condensation plug.. it has vent tubes on the top of the bellhousing from looking at the parts diagram. Interesting machine but not normal.