FLU419 SEE Wheel Hubs

[Gringo]

Used the SEE to Clean out a small pond for about a week, it did well but I pushed it pretty hard.


A day or two later I finally cut a tire while clearing brush, sidewall ripped open by large rock.

While changing that tire I noticed a fairly significant leak coming from the other front wheel {Drivers side}. Having just recently read the posts/warnings from Speedwobble about checking/changing the oil in the Hub's I immediately went and got some 80/90 gear oil and drained and refilled all 4 wheel hubs as well as the transmission an differentials. Noticed in general that most of the drain plugs with magnets were covered in a mixture of oil with fine metallic looking material. I Figured this was probably normal wear and tear for a vehicle this old etc...and that since I have only had the vehicle for a few months that it could have been years since it had been changed.



Cleared brush for another few hours the next day with no leakage, then the following day I used the SEE at fairly high speeds while rebuilding a road ( going back and forth to the material pile was about .75 mile away from the actual roadwork) Towards the end of the day I noticed the steering became difficult and that the vehicle itself seemed a little sluggish or possibly acting as if it was in 4wd even though it wasn't supposed to be. Parked it and the next morning the front drivers side wheel was leaking again so I drained it and the other wheels again. This time I looked more carefully at the oil coming out and found a thin piece of metal shaving that was about 1/4 inch long when I drained the front wheel. The other wheels had mostly clear oil although I also found a much smaller metal shaving piece that came out of one of the rear wheels.



Does this mean I have a blown/failed drivers side front Hub? and another one about to go on the rear? or is it in the process of failing, but not actually at that point just yet and could maybe be saved by replacing a few parts?

Any advice is much appreciated.

 

[peakbagger]

you might want to search for 4o6 hubs on Benz World. They have deeper experience base on things Mog (but not as tuned into SEE's)

 

[The FLU farm]

Sounds like you may have overheated the hubs, and I do remember reading that they like to spit oil out when driven fast.
Are they back to normal after having felt like you were in 4WD?

 

[peakbagger]

Sounds like you may have overheated the hubs, and I do remember reading that they like to spit oil out when driven fast.
Are they back to normal after having felt like you were in 4WD?

Not sure about spitting out oil when driven high speeds. The usual issue with folks who drive high speed is that the oil from the hubs get driven up into the axle through the air pressurization system. Generally its the drivers side front wheel that is the problem. Most Mog folks who drive highways speeds check their hub temps with an IT thermometer and look for differences in temp between the wheels. I think the OP just has blown hub seal.

Another possibility is an failed air pressure regulator on the 4wd pressurization circuit. When 4WD is engaged, there is regulator that supplies low pressure air to the axles and hubs to prevent water from getting inside. If the regulator fails and full pressure is applied, it will blow seals in a heartbeat. Many Mog drivers who do not drive in water routines disconnect this system or set it up with solenoid so that they have to manually engage it. This system is also a source of air leaks.

 

[Gringo]

The vehicle seems to be back to driving normally again as best I can tell, although I haven't driven it at higher speeds for long enough to say for sure.

I have drained the Hub 5 or 6 times now and after each time I take it for a spin and then let sit overnight. Usually the next morning I can see a very small leak/ slow drip coming from the part of the Hub assembly that connects to the steering linkage ( in the picture I posted above it would be the medium sized bolt just beside and to the left of the drain plug bolt in the picture). All three other hub's are completely clear and free when I check or drain them, however the drivers side still contains metallic particles. This leads me to believe that the Hub is slowly chewing itself up. Don't have any idea how long this process could take, whether it has a year or a week left before finally "failing" which to me means becoming un-driveable.


As much as I have now read about the Unimog Axles/Reduction Hubs I would have expected to find lots of examples and first hand descriptions of various Hub failures and how long in between the initial outward evidence (Leak) or physical manifestation (handling behavior or performance issues) and the final full and complete Failure etc... However so far Bill Caid's website is the only place I have found detailed info on such and of course his experiences didn't involve a 419.


I believe Peakbagger's analysis is pretty close except that I do not yet know whether or not the 4WD air regulator had anything to do with the original oil seal failure or if was just due to mud being caked onto the inside of the wheel/hub for a few days in a row while digging out the pond. Then most likely after that seal failure some mud or dirt found its way inside to the Reduction Gears/Bearings and started slowly wreaking Havoc. Not sure how long it has left so I have started pricing parts and/or replacements. From what I gather so far all of the replacement parts to rebuild the Hub will run about $2k of which the Gears constitute about 2/3's of the cost.


Next issue is where to take it to get rebuilt, I have stopped by a few machine shops all of which seem competent and say they should be able to rebuild it although none of them have ever worked on a Unimog before. Plus I imagine I would be paying them by the hour to learn as they go. So I am also considering just getting a whole new/refurbished front axle from C and C Equipment, but would probably run into the same issues with installation by one of the local shops without prior experience. That is unless someone out there reading this with more knowledge and experience loves hunting Exotics and wants to come to Texas to fix it for me

 

[The FLU farm]

Not sure if there are any left, but I remember seeing complete new or rebuilt axle assemblies for sale at surprisingly low cost.
You may want to poke around on the interweb a bit.

 

[tennmogger]

It is difficult to diagnose wear in a Unimog hub without going inside and looking. Probably the most common failure is spalling in the bottom of the race for the big wheel bearing. One cause scenario is that any small contamination like sand grains or metal flakes tend to settle at the bottom of the reservoir, and that puts the trash in the bearing, which is then damaged when driven again.

There is little if any heat build up as the bearing eats itself, and you can't hear the problem while rotating the tire/wheel. But you can feel the wear problem by pushing and pulling the top of the tire. If there is noticeable and measurable movement (other than a perceptible 'bump' you can 'feel' which is normal) then work is needed. A wearing bearing is not a fast failure, and usually not catastrophic, like lockup.

If the reservoir continues to produce glitter, then you should start saving for a rebuild. If the hubs are the same as on a 406 or 416 then good used parts can be picked up reasonably. Lots of Case MB-4/94 Unimogs were treated horribly and got eaten up by salt over the years, and are being parted out. Check with Von Kittelberger at Vonsmog.com. He would probably know if the gears and bearings are same as a 419, and have parts.

Looking more closely at the pictures, I think you have a blown upper oil seal, the seal around the axle on the inner side of the hub. That requires a tear down. Or, there is a way to cheat. If you fill the hub with NLGI-0 grease (aka Corn-head grease) the grease will not leak out. There are some good videos on the web of how NLGI-0 grease liquefies with motion, but coagulates if not stirred. Great stuff for old trucks but some folks think that's cheating. The grease will also mobilize the chips and other wear products to keep it out of the bearings.

BTW, just because the bearing is going, the gears may still be good, but new seals are always called for.

 

[Speedwoble]

Yeah, before I would order parts, or a new axle, I would take it apart and see what is wrong. May only be a bearing and some seals. Doesn’t sound like it has chewed a lot of metal yet.

 

[Gringo]

Yeah, that's exactly what I'm doing.

As I was "flushing" the Hub (on the 6th or seventh flush by the way) I found a piece of metal that was large enough to see letters on it.

I assume its part of one of the Gears, probably the larger lower, but I don't know for certain yet although the picture may also give a hint towards

the upper Gear as the whole at the top is the dirtiest one or maybe that's just how Gear Oil works itself out of an upper seal etc...

Found a guy who runs an offroad shop in town who has an older Unimog rock-crawler who said he could rebuild it but wanted me to just bring him the hub after it had been removed from the vehicle. I guess he doesn't want it crowding up half of the shop while waiting for the parts once we find out exactly what all is needed. Plus I figured the 40 mile drive probably wouldn't help things much either.

However, I can't seem to get the Steering knuckle over the upper "kingpin" in order to remove the hub assembly. I wasn't planning on removing/replacing the bearings in the steering knuckle especially since the bottom of the assembly was already free/ready to come off, but I guess I am going to have to pull out the "joint bearing" or whatever the bearing that's just under the upper kingpin is called. Got the screws, lube fitting, cover, and the seal/washer off of it, and thought perhaps I could just lift the top of the assembly up and over the rest of it in order to get it to the shop so at least I will know exactly what to order.

Apparently its more of a "ball joint" than a "pin" and just keeps swiveling. So I looked at trying to use a couple of Pullers for tie rods and other various front end related items with no luck. Interestingly enough the lower bearing and seals voluntarily surrendered as I was lifting and twisting the hub assembly fighting with the topside. Called it quits just before dark, to eat and do some recon. From what I can gather so far the upper steering knuckle bearing has tiny grooving in the center and recesses on parts of the outer edges designed to be removed by a specific "Extractor" in conjunction with a Puller. Of course you cant just grab these at the local parts store.

Looked at Exped Imp website and they are out of stock. I am sure there must be some kind of "bush fix" to get that hub assembly off, but so far I have not figured one out other than maybe just going to town with a sledgehammer and breaking more stuff. Hopefully that's where you kind Gent's come in and save the day.

 

[peakbagger]

I have not done the repair or taken the assembly apart. That said it looks like you need an expanding inner bearing race puller. Here is a link to what you appear to need http://www.skf.com/us/products/main...g/bearing-pullers/internal-pullers/index.html

I would definitely set up a job ticket with Expedition import and inquire if they have the tool. I haven't done it but apparently they have lent specialty tools out in the past.

Either that or contact Vons Mogs and see if he can help.

Mercedes does use a lot of specialty tools. I haven't seen a set for the SEEs but on occasion I see sets of specialty service tools for specific product on the German Ebay site. I expect somewhere sitting on a pallet in US military warehouse are a couple of sets in cosmoline but the odds of actually getting hands on them is slim to none. Then again Sgt Hood found the wiring diagrams on a government auction so its possible.