Rear Wheel Bearing Torque

[whitecc250]

Can someone help me with obtaining the correct procedure for reinstallation of the rear wheel hub on a 1981 R-Model with the standard rear end housing. Information needed especially in relation to bearing preload, axle nut torque, etc.? We had some issues with rear wheel studs, which involved removal of the entire hub assembly. After replacing studs and reinstalling the hub, we were rolling along, only to be shutdown on the side of road with hub coming off. It appears that bearings came apart or axle nut backed off allowing hub to seperate from the axle housing. We have done this procedure several times before when changing brake shoes and not had issues. Thought that maybe we had missed some important step, (such as loctite on nuts, etc) and want to get it right this time so as not to have a repeat failure.

Thanks for any input.

[HK Trucking]

Can someone help me with obtaining the correct procedure for reinstallation of the rear wheel hub on a 1981 R-Model with the standard rear end housing. Information needed especially in relation to bearing preload, axle nut torque, etc.? We had some issues with rear wheel studs, which involved removal of the entire hub assembly. After replacing studs and reinstalling the hub, we were rolling along, only to be shutdown on the side of road with hub coming off. It appears that bearings came apart or axle nut backed off allowing hub to seperate from the axle housing. We have done this procedure several times before when changing brake shoes and not had issues. Thought that maybe we had missed some important step, (such as loctite on nuts, etc) and want to get it right this time so as not to have a repeat failure.

Thanks for any input.

I'll assume that you're saying you've got the 38,000 or 44,000 lb. Mack rears with the 4" adjusting nut, lock ring and jam nut.

First, be sure to pre fill the cavity between the inner & outer wheel bearings with gear lube before installing the outer bearing.

Install the adjusting nut (making sure the "dowel" is pointing outward), torque to 100 ft lb, spin the hub a couple turns in each direction to seat the bearing, back off the nut about 1 turn, tighten the nut again to 50 ft lb., spin the hub again, then back off the adjusting nut 1/4 turn.

The bearings are now adjusted.

Next, install the lock ring onto the spindle, making sure the dowel on the adjusting nut is in one of the holes in the lock ring.

Then install the lock nut, I always tighten the lock nut as tight as possible with a breaker bar and pipe, then I use a chisel on the edge of the nut, and a couple good hits with a hammer (in the direction of tightening) to give it a little extra assurance that the lock nut is tight.

Before re installing the axle shaft, I always add a couple pints of gear lube to the differential by shoving the dispenser hose down the axle tube. This assures that there is enough lube in the diff to fill the wheel end once the truck is in operation.

[whitecc250]

Thanks HK Trucking. Yes, I was referring to the 38000 lb. rear axle. Sorry for omitting that important piece of info. The way that you described is the near exact way that we reinstalled the hub, this time. I think that the previous attempt and failure was from either the Jam nut backing off from being too loose, or reinstalling the bearings with no oil added and resulting in them running dry and getting hot before any oil from differential made its way to the bearings. I had not been involved in previous attempt, but wanted to make sure that we did not miss any thing this time. We even went as far as running the opposite side wheels up on boards to elevate the carrier and allow oil to flow to the outer side for about 5 min and then rechecked the level. As of this post, the truck has made several loads with no problems.

Thanks again for your confirmation that we were on the right track.

Edited May 16, 2009 by whitecc250