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packing bearings
Techs out there - please advise!
I know this isn't a Mercedes but please advise. I have a Gulfstream RV on a Toyota chassis. It has duel rear wheels. I pulled the hubs, axles, and drums this weekend to find out where the grinding noise was coming from. Turned out to be a fried outer wheel bearing. I know I cleaned out at least a pound of grease out of each hub. My question is is it necessary to fill the hub with that much grease, or just pack the bearings good and reassemble? Anyone have anything to say about Mobil 1 synthetic grease? (cool purple color) Thanks all, Robert Davis
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Robert Davis |
#2
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My Mobil I synthetic grease has a cool red color!
I hope you replaced the entire set when replacing the bearing. This means both races and rollers. When repacking conventional wheel bearings, you have to play "goldilocks" with the amount of grease.... not too much and not too little. Too little will shorten the grease life. Too much will cause the bearings to overheat. I work for the bearing industry and our specifications not only have a min but also a max on the amount of grease. First, all old grease must be cleaned out. When repacking, the grease has to be fully packed into the roller assembly. This is commonly done by scraping the taper roller assembly against a glob of grease in the palm of your hand. Keep going around the roller assy until grease comes out the other side. Next, all interior surfaces of the bearing hub cavity are buttered with a light coating of grease. Place the roller assembly into the race and add some more grease to cover the roller sides (both sides). The axle is now properly greased. Though not specified, some people pack the cap with grease before installation. They say it provides a measure of protection should the bearing overheat for some reason. Use new seals. Make sure you properly set the preload on the bearing. In the absence of a specified procedure, first tighten the axle nut while rotating the wheel (about 40 ft-lbs). Then back off the nut and tighten finger-tight. Then install the cotter pin mechanism. If none of the cotter pin holes line up, back the axle nut off just a bit for the best fit.
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95 E320 Cabriolet, 159K |
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That was a great how-to. The only thing I'd like to add is the dustcap is lightly greased to keep condensation from rusting the inside of the cap.
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83 M-B 300D- daily driver 83 240D gray market 2002 VW Jetta TDI- beater |
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I agree, great how to man!!
Quote:
I talked to a Mechanic recently who said it is a pretty un-precise procedure in most Mercedes... he never measures. |
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None of our automotive or truck product specifies packing grease into the dust cap. Except for perhaps wasting some grease, I don't see any problem with it. In fact, like I said earlier, in dire circumstances it may help the car limp along a little farther. Properly specified grease doesn't heat up and flow like oil. After all, how many times have you taken a wheel apart and found the grease intact in the hub, just like it was left? If it flowed like oil you'd probably get good mixing (churning) of the grease with very few dead spots.
No two people grease alike. Some may butter the insides a little heavier. There's nothing wrong with putting the extra inside the cap. I don't measure my grease either. I simply follow good regreasing techniques. I think it's very thoughtful of MB to specify a certain grease charge to prevent people from getting too enthusiastic about lubrication.
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95 E320 Cabriolet, 159K |
#6
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I believe that grease behaves very much like an oil when it is heated... here, let me find an old post.
This is from JimSmith in response to my post here: http://www.peachparts.com/shopforum/showthread.php?threadid=71444&highlight=wheel+bearings Quote:
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#7
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Screeeeeeeeeeeeeeeeeeeech! Hold on everyone.
Robert, are you dealing with a "floater style rear differential? I bet you are because of the inner and outer wheel bearings that I think you described. A simple discription is one where you pull the axle out first and then the break drum comes off. That type of setup is lubricated from the differential lubricant. The lube runs out of the axle tube and fills the well between the wheel bearings so that the bearings run in that 90 weight gear lube. Wheel bearings fail in this type of setup most often because the rear diff is allowed to run low. If it is just 1/2 inch low there will be no lube moved to the axle. Fry baby Fry!!! |
#8
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By the way, that pound of grease you pulled out probably contributed to the bearing failure by keeping the differential lube out. Just for fun, tell me how low your diff level is. Use a piece of wire and stick in the fill plug. Oil should run out when you pull the plug of a full diferential.
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