TOP IMAGE: Low Pressure for off-road work. Large area,
low contact pressure = good traction, low wear. Maximum ground protection, good auto-cleaning.
BOTTOM IMAGE: High Pressure for road travel. Small area,
high contact pressure = low rolling resitance, low wear. Good traction at high speed.
I'm posting the following for those U-900/406ers (including the Case MB4/94) of you who are anticipating replacing front axle output seals. The old-style seals haven't been used since about 1985 and the modification involves some simple benchwork. This up-grade is indicated if there is seal failure *and/or* wear on the axle shaft at the old seal's point of contact.
I have translated this from my German copy of the Mercedes-Benz Service Information dated July/85 from Gaggenau. The following is valid for *BOTH DRUM AND DISK* brake types. For drum brake front axles on UNIMOG types: 403, 406, 413, 416, and 421. (For 406 drum type axles, i.e.. 737.001 as well as 737.030, .031, .032, only up to *AXLE* number I-002695). It is also valid for DISK brake type axles on UNIMOG types 403, 406, 413, 416, 417. (For disk type axles 737.101, .030, .032 only up to *CHASSIS* number 136115). The vast majority of 406s, etc., in the U.S.A. will have chassis numbers within these application validities. Feel free to call or email if you need help.
Here it is.
First, remove the old bronze axle output bushing. It is usually cracked and/or out of round. Install a new bushing (P/N 406 332 10 50) into the axle tube. The bushing is properly seated when the lip is flush with the cast axle housing. Handle the bronze carefully.
With the axle shaft assembly (including C-V joint) on the bench, measure from the center of the inboard knuckle pin (see schematic at measurement "a" - highlighted in yellow) back along the axle shaft for 35mm +/- .5mm. Mark this point with a scribe (or temporarily tighten a hose clamp at this point). This is the point where the wear ring (P/N 416 337 08 51), at the end closest to the C-V joint, is to sit.
Apply some Loctite 241, or equivalent, around the axle shaft where the wear ring will seat.
Warm the wear ring to circa 90 degrees Centigrade (194 F.) then pull it to the prescribed location.
Apply a durable grease to the new lip seal (P/N 012 997 34 47) and install into axle housing using seal installer tools (Mercedes-Benz) numbered 440 589 01 43 00 and 406 589 04 15 00, or the equivalents. The seal is seated when it comes to rest at the stop cast into the housing.
Insert axle shaft and re-assemble.
Hope this helps.