Crawled under the D6C today to grease the track roller frame bushings to find a couple issues. The RH final drive oil level was a bit lower than the left (~1/2" lower), when I got underneath I found this leak: imgur.com/Ja6EqmO

This doesn't look like an easy seal to replace...

On the RH side there is no leak, but the snap ring has come off the lock nut ( imgur.com/ieoOKIs ), and the pin on the shaft just so happened to be facing down, pin was still in, and I was able to get the ring back on, no idea how long it was like that... I don't have an overhaul manual for this tractor, and not sure by looking in the parts book where the leaking seal is actually located. The leak is more of a weep than a leak. Is this likely due to just seal hardening or is it indicative of a larger issue?

There is no seal there, I'm afraid, just a taper press fit.
For a machine that sees such little use I would check that the nut is tight and hope for the best.
The other option is to open up your wallet and your final drive.

"Glum" wrote:

There is no seal there, I'm afraid, just a taper press fit.
For a machine that sees such little use I would check that the nut is tight and hope for the best.
The other option is to open up your wallet and your final drive.

So the nut is just sealing a taper? I'm wondering about the locking pin clocking, I'd need to go 1/2 turn or is there more that one hole in the shaft?

Sealing relies just on the fit of shaft to casing.The nut keeps the sprocket shaft tight once it is pressed in to the casing to the correct tonnage and distance. If you are able to tighten the nut you drill a new hole in it to locate the locking pin.

"Glum" wrote:

Sealing relies just on the fit of shaft to casing.The nut keeps the sprocket shaft tight once it is pressed in to the casing to the correct tonnage and distance. If you are able to tighten the nut you drill a new hole in it to locate the locking pin.

Does the track/sprocket need to be off the ground while I try to tighten this nut?

Wouldn't hurt to jack it up but if its not leaking more than a seep i doubt it will be loose enough to matter whether it is jacked up or not.

That kind of thing is always press fit with clean DRY surfaces. So it obviously has oil on it but that might help you get it tight. I would back the nut off and oil the threads before trying to tighten it up. You are trying to use the nut to do what a hydraulic press should be doing but you have lube to make it slicker than normal. Unfortunately the nut may be under more strain because of the oily, worn?? taper and not stand up to the (ab)use.

I would keep a check on how tight it is while operating the tractor a while. Retighten until it quits tightening up or obviously isn't holding. If it gets tight and stays tight under use then drill another hole for the pin if needed.

If it won't tighten, or will not stay tight under use then you will have to disassemble and see about fixing it properly. I wonder if a slightly worn socket might do ok with a new dead axle installed over something like loc-tite 660 compound. I think the caterpillar dealer will have a way to ream and install a bushing for $$$$.

Note.......when you tighten the nut retaining the dead axle into the housing, you are tightening the final drive bearings at the same time. This is probably good unless you get dead axle retaining nut to move much or have recently adjusted the final drive bearings up tight with the adjuster on the outside of the sprocket hub.

So, if the dead axle taper has loosened up, what do we think the cause would have been? It's odd that it's just a taper fit and no key to keep it from spinning and opening up the hole bigger...

And what are the dangers of using it as-is for about 3-4 hours grading crusher run on my driveway? I don't have much work left for this tractor. I'm going to change the engine oil, new air filters, new fuel filters, fix the tilt cylinder hoses, do my driveway and the machine likely gets parked for many years. If I ever restore the tractor I'll worry about the dead axle then. But for now, if the nut doesn't move at all, and I use the tractor for a few hours to push stone on a level surface, do I risk any catastrophic damage?

It wasn't Caterpillar's finest bit of engineering. Its probably been like that all the time you've had it and unlikely anything will happen for many hours but don't hold me to that.

"Glum" wrote:

It wasn't Caterpillar's finest bit of engineering. Its probably been like that all the time you've had it and unlikely anything will happen for many hours but don't hold me to that.

Yeah, I can't say that it hasn't been weeping like that for the ~1000 hours I put on the machine since 2005 when I got it... This is just the first time I have noticed it. I suppose I should put a magnet down into the final drive just in case, but it's not like I am going to spend the $10k required to rebuild it. I'd probably park the machine and that's that.

I removed the ring and pin, and was able to turn the lock nut about 1 inch on the diameter, which is about 18 degrees. I don't know the thread pitch on the shaft, but if I can find that info I can calculate the axial movement of the taper. It was turning and then seated pretty solid. I was using a 6 lb sledge and a drift pin, not sure what kind of torque I was able to achieve.