Now we have the rig jacked up and the front wheels off. On most big rigs the wheel bearing cover is held on by a circle of bolts, either 5/16ths or 3/8ths bolts. The lighter rigs, class C’s and B’s for the most part still use the stamped steel hub caps that knock right off.
The big rigs the cap is a casting on most and has a gasket between the cap and the hub. Preserve that gasket or use a new one when re installing. I usually use the red RTV (room temperature vulcanizing) gasket material. The trick to using that stuff is to put down a continuous bead about 3/32nds thick. Then let it almost dry to the touch before installing. That way the center of the material is still somewhat fluid but the outside is stiff holding the material in place.
Before taking off the nut that holds the wheel bearing in place the disc brake caliper will have to be removed. Do not let the calipers hang down on the brake hoses. Bungee cords can be used to hold them up or the good old million dollar bent wire coat hanger.
Now remove the outer retaining nut. Lighter rigs will have a cotter pin to keep the nut from turning while some bigger rigs will use a lock nut that must be removed first. I usually have a coffee can ready to put the parts into as they come off as you will want to keep grit and dirt out of them.
Once the nut is removed you can usually shake the rotor and cause the outer wheel bearing to pop part way out so that you can grab it. Once it is out then the rotor will slide off the spindle but take care as the rotor slides off that you hold it up so that the treads are not damaged and do not damage the inside bearing. Now lay the rotor down with the inner bearing down on a clean rag and using a small long block of wood tap the inner bearing and seal out of the rotor hub onto the rag.
Now there are tow schools of thought on the next step, the cleaning. If when I take the bearings out I do not see any signs of grit or metal flakes I will wipe all the old lubrication off the bearings that I can and then go right to packing. If I see signs of contamination I will use a solvent and clean the bearings. An old timer explained to me once long ago when we were sitting around the old campfire that using solvent when not needed was like taking the season out of a cast iron frying pan by washing it too strongly. Solvent, he claims, gets into the pores of the metal and effects the lubrication.
Now I use a wheel bearing packing device that I bought from Gemlers catalouge that sells for about 10 bucks. You put the bearing in the device, attach your grease gun to the fitting, and pump away until fresh grease comes out of the bearing. Clean the inside of the hub cavity and apply a thin layer of grease to the cavity and re assemble. Use care when installing the inner bearing and the new grease seal. I use a short length of 4 X 4 as a driver to drive the inner seal in square to prevent damage. Re-install everything and adjust the bearings as we talked about last week and you are good to go. Remember that not enough grease is bad and too much grease is bad. Good luck and tune in next week for another exciting chapter in “getting my hands dirty.”
Brad