x55 series MFWD final drives

[Mechanos]

I wasted a couple of hours, some gear oil and fair amount of money yesterday. I noticed a slop in the front wheels (wheels will wiggle back and forth) of my 955 and chalked it up to worn out steering cylinder rod ends and worn tie rod ends. Swapped out the steering cylinder for a good one on one of my parts donors, fixed the tie rod ends and that took care of most of the slop. There is still a little slop there and figured it was the bearings in the final drive. Picke up new inner and outer bearings, oil seals, oil seal wear sleeves and final drive cover gaskets and went to work changing out the bearings.

The inner bearing on the left side was still good. Tight and smoothe, so I did not replace it. The outer bearing was a kind of rough and the wear sleeve was well worn, so those got replace along with the oil seal. I temp bolted the cover back on without the gasket and slop was still there. After doing some more investigating, the source of the slop is the fit between the splines on the stub shaft and final drive gear. There is now way to tight this up short of replacing the stub shaft and final drive gear and at $600 per side, that's not going to happen anytime soon.

I did some checking and the other side has a little slop the stub shafts on an 855 axle I have also have some slop. So, I'm assuming this is normal to some degree. I cannot find any documentation of how much slop is normal or allowable.

 

[unimog_jason]

I found the same thing shortly after buying my 755. At first I thought the front bearings were shot and should be replaced.

I have a fair amount of experience with portal boxes on Unimogs and as soon as you find a slight amount of play you redo the bearings. One symptom you can always count on is oil loss from the portal.

After thinking about this for a bit I realized that the front portal boxes on my 755 are almost completely full of oil but they won't leak a drop, so things must be ok inside.

I've had the tractor for over 3 years now and done a lot of loader work and the front end is still ok, so I don't loose any sleep over the slop.

Jason

 

[Mechanos]

Yeah, that's pretty much the conclusion I've come to as well. The design of the x55 series final drives is probably a bit different that the 'mog portals. The bearings, both inner and outer, support the final ring gear. The stub shaft just presses into the ring gear and is held in place with a snap ring. I would expect the splined fit between the two to be a bit tighter than it was, that is the source of the slop.

Once I looked at my other x55 front axle, and found the same thing, I decided that is just the nature of this design. I"m just going to run it as is and keep an eye on it. If it gets real bad, I'll look at replacing the stub and ring gear.