Changigng Oil in My 753 Chain Case

[USN Retired]

I am about to change the chain case oil in my 753. From reading some of the threads it sounds like there should be 9 gallons in the chain case...correct? As I intend on pulling the chain case cover to clean the chain case will there be a gasket which will need replacing? Since I have the cover off I may as well fill the chain case at that time. Is this the correct way to add oil ? When I originally checked the oil level by pulling the chain case oil plug on the front of the machine oil came out. Should oil only be level with the plug?

 

[OldMachinist]

The manual I have says 8 gallons. There is a gasket on the cover and should be replaced. You can cut one yourself. Yes with the machine on a level surface the oil level should be even with the front plug. There are two reasons why the chaincase would be overfull the first would be if the cover gaskets are letting rain water leak in and the second is one or both of the drive motors have a leaking seal which allows hydraulic oil into the tank. Removing the cover to drain and refill is the best way in my opinion as it allows you inspect the chains and sprockets.

 

[USN Retired]

The manual I have says 8 gallons. There is a gasket on the cover and should be replaced. You can cut one yourself. Yes with the machine on a level surface the oil level should be even with the front plug. There are two reasons why the chaincase would be overfull the first would be if the cover gaskets are letting rain water leak in and the second is one or both of the drive motors have a leaking seal which allows hydraulic oil into the tank. Removing the cover to drain and refill is the best way in my opinion as it allows you inspect the chains and sprockets.

Thanks for the reply...my thoughts exactly. There is a forward plate (with the orange brake sensor on it) and the large after plate. Should I remove both plates?

 

[OldMachinist]

Thanks for the reply...my thoughts exactly. There is a forward plate (with the orange brake sensor on it) and the large after plate. Should I remove both plates?

If you find water in the oil and plan to store the machine outdoors then I would reseal the back plate also. The front plate comes loose alot of times because the traction lock(brake) is bolted to it.

 

[USN Retired]

If you find water in the oil and plan to store the machine outdoors then I would reseal the back plate also. The front plate comes loose alot of times because the traction lock(brake) is bolted to it.

I will do both...better safe then sorry. Thanks again!

 

[HarryN]

I will do both...better safe then sorry. Thanks again!

Every one is right on.....when I changed the chain case on my 763, some water did leak under the gaskets. (Was milky) I changed both gaskets (about $8 each from Bobcat) My 763 takes 9 gallons. Instead of taking out the drain plug (because I didn't have a replacement plug), I pumped it out thru the cover, flushed out the case with diesel, then filled with Rotella 15W40. Same oil I use for the engine too!

 

[HarryN]

Every one is right on.....when I changed the chain case on my 763, some water did leak under the gaskets. (Was milky) I changed both gaskets (about $8 each from Bobcat) My 763 takes 9 gallons. Instead of taking out the drain plug (because I didn't have a replacement plug), I pumped it out thru the cover, flushed out the case with diesel, then filled with Rotella 15W40. Same oil I use for the engine too!

Wonder if this picture was a better fit? (so you can see the milky oil....)

 

[USN Retired]

Every one is right on.....when I changed the chain case on my 763, some water did leak under the gaskets. (Was milky) I changed both gaskets (about $8 each from Bobcat) My 763 takes 9 gallons. Instead of taking out the drain plug (because I didn't have a replacement plug), I pumped it out thru the cover, flushed out the case with diesel, then filled with Rotella 15W40. Same oil I use for the engine too!

When I drained it the oil was milky. Of course it had been setting outside for a few years. When I took the chain case covers off both appeared to have places where water had gotten in. One of the previous comments said it is possible there could be a hydraulic leak from the drive motors. How would I know this? Since I cleaned the case all seems to be okay. Would it only happen if running? After I replaced worn hoses and all the piston seals on the arms and bucket I have not noticed any change in my hydraulic oil level.

 

[HarryN]

When I drained it the oil was milky. Of course it had been setting outside for a few years. When I took the chain case covers off both appeared to have places where water had gotten in. One of the previous comments said it is possible there could be a hydraulic leak from the drive motors. How would I know this? Since I cleaned the case all seems to be okay. Would it only happen if running? After I replaced worn hoses and all the piston seals on the arms and bucket I have not noticed any change in my hydraulic oil level.

Not sure on a 753 as I have a 763. Maybe someone could explain how a hydraulic leak from the drive motors could get into the chain case?? Anyway, if you've filled it to the top of the front drain plug on a level surface, then check again later with no increase, you're good. Water was probably the problem for you. No change in your hydraulic oil level and all is working/ no leaks........ is even better!

 

[OldMachinist]

Not sure on a 753 as I have a 763. Maybe someone could explain how a hydraulic leak from the drive motors could get into the chain case?? Anyway, if you've filled it to the top of the front drain plug on a level surface, then check again later with no increase, you're good. Water was probably the problem for you. No change in your hydraulic oil level and all is working/ no leaks........ is even better!

The drive motors bolt right on the sides of the chaincase and they have seals that can sometimes start leaking. If the motor seals were leaking you would see your hydraulic fluid level drop and the case level rise over time.

 

[7LBSSMALLIE]

every post are mostly correct. my onl issue is do not use the gaskets. they do not work. oil will wick out .i poly seal (dealer should have it) or quality silicone sealant, secondly it is not the drive motors leaking but the carrier seals, rarerly is the motor responsabile there are two reasons when it is the motor one bolts backed out wiping out seal vissable damage is apperent. two exessive case drain leakage in motor.rare but happens inspection of the case drain filters will usauly show it, or quit possibly the carrier brgs themselves. do remove center cover and inspect brake discs and carriers. bytheway the removal of steering console will make life eiser takes 10 min and placing a magnet in case below filler hole is not a bad idea.