a little write up on dealing with the hubs on
full-floating HO52 / HO72 Eaton rear ends (5,200lb & 7,200lb
ratings) that came under 1947-1972 GM 3/4 ton and 1 ton trucks
so you can work on the wheel bearings/seals/brakes. The basic process
applies to other full-floating rear ends and all the part numbers listed here
are actually the same as the very popular 10.5" 14 bolt FF that
replaced the Eaton in '73.
|Remove the eight bolts in the axle flange. Keep a catch pan underneath the hub for the oil that will pour out (gear oil takes a while to ooze out of there, so just doing this to both sides and walking away for a little while as it drains probably isn't a bad idea). Clean everything up before this so that you don't get dirt and grit in everything (a better arrangement for jacking the truck up and holding it there would probably also be a good idea...lol).|
|Now you can slide out the axle. There are two threaded holes in the flanges that you can thread bolts into for this, but they should just slide right out (if they are all siliconed up you may need to smack them sideways with a mallet or something to get them loose).|
|Now it's time to take the bearing nuts off. There is a stamped steel lockwasher with little tabs to bend over and lock the outer nut in place; bend the in-use tab back out of the way with a screwdriver or something.|
|Now you take off the outer nut. This one just locks everything down tight, so it may (theoretically speaking, should) be on there pretty damn good. Some people will use a punch/screwdriver and hammer for dealing with these nuts, but the proper socket is relatively inexpensive ($15-30?) and easy to come by; this particular one is a K-D 2770 that is actually listed for later 4x4 applications--it's just a 2-5/8" OD socket with six outer lugs. You may have to resort to the hammer and punch/chisel method to get it off if someone has already messed it up. The nuts are Dorman part # 615-130.|
|Remove the tabbed lock washer; note the tab that's bent in to hold the inner adjusting nut in place. The part # for it is Dorman 618-049. Set it aside and remove the inner adjusting nut.|
|Don't forget about the keyed washer that goes between the nut and bearing (I like to go ahead and remove it now, before I get the chance to drop it in the dirt). The part # is Dorman 618-048 if you need it.|
the hub and drum assembly can be taken off. They are pretty heavy
(around 50lbs), so keep that in mind. Take them off and set them aside.
Gear oil will probably still be oozing out of them at this point, so be aware of that (this is the main reason why I recommend setting them in a pan or something).
it's time to inspect eveything, clean it all up, and put it
Note that the seal surface is pitted in this case; a "speedi-sleeve" is available that you can slip on over the pitted surface to prevent any leakage. The hub seal itself is National/Timkin # 2081 / SKF # 28426 and the sleeve is National/SKF # 99282 (SKF also has a "kit" consisting of the # 28426 seal and # 99282 sleeve as # 28446). Wipe some grease in the seal lip to lubricate it before installing the hub.
Clean up the hub flange surfaces and axle flanges to insure you don't get any leaks.
|If you got any grit/dirt in the hubs and bearings you'll need to clean them. The outer bearing is retained by a snap ring inside the hub and comes out from the inside (should be pretty self-explanatory). Some say to pack them with grease, some don't; I personally like to just coat them in the same gear oil they run in (more on this later).|
|Slide the hub on (being careful not to damage the seal...or explode the outer bearing into a bunch of loose rollers that you then have to find in the grass and deal with--don't ask!), insert the keyed washer, and thread the inner/bearing adjustment nut on.|
|Here are the torque specs from my '67 GM Chassis Manual. I tried this, but found that backing off 1/8 of a turn was pretty much just the point all the slack was taken out--which would be fine, but when you lock the outer nut down on top of it the play in the threads clamps down on the bearing whatever that additional amount is. Maybe this is the spec, but I found that (at least in my case) it made the bearings kind of tight and the hub on the side I tested seemed noticeably hotter than the other; the bearings were obviously getting somewhat hot. I really didn't like that very much.|
|Same thing here, but they seem to say to back off one more slot past the nearest after the initial adjustment? Maybe just for the 10.5" 14 bolt, where they don't mention backing the nut off a specified amount at all? I don't know.|
|I ended up setting them up by trial and error to my liking; I just tried to find a setting where the play was just taken out or very minimal when the outer nut was threaded on and tightened up. I adjusted the inner nut until I could feel/hear a little movement/play in the bearings when pulling on the drum (as described in the scanned page above), then tightened up the outer nut and checked again. If it was still loose I would tighten the inner nut to the next notch and try again, if it was tight (or I thought it might be) I would go the other way and see what that was like--same as you would with the front wheel bearings. Works for me.|
|The axle flange gasket is Fel-Pro # 55350. I don't really like silicone in places like this and would use something like a (very light) coat of Permatex #3 if you wanted to use something. Slide the axles back in and tighten the bolts to 90ftlbs.|
|Now you should make sure the hubs have oil in them. I like to top the oil off and jack up one side of the truck/rear end at a time so the oil runs down the axle tubes to the hubs; I pull whichever axle flange bolt is on the bottom out to verify oil runs out and call it a day. Another option would be to add some into one of the upper bolt holes with something.|
|Done! Check the hubs next time you drive the truck to make sure something stupid isn't happening and they aren't getting hot (or are loose, etc.), but you should be good.|