Brake Drum Removal: M500, '79 Chieftain

[The_Handier_Man1]

Original Discussion posted by:  jddrivfour

My chassis manual does not make it clear how to remove brake drum. I ttok the whhels off ,then the nuts off the studs in the hub center. I cannot figure out how all this is assembled. My objective is to inspect the brake linings.
1979 Chieftain
Thanks



From: Slantsixness
Sent: 2/20/2005 11:55 PM

Pull the axle(center axle nuts and cones) then the bearing nut. and then it all comes apart.

the following is from the M series service manual:
(2) remove wheel and tire
(3) remove axle shafr nuts, washers and cones. Rap axle shaft sharply in center to release cones if they do not readily release. Remove axle shaft.
(4) using tool DD-1245 remove outer hub nut. Straighten lockwasher, remove it, inner nut and bearing. carefully remove drum.
Caution: If there is interference between brake shoes and drum, remove hole cover and using a screwdriver and light piece of metal, release brake shoes (fig.6)

you have some larger tools (this nut is BIG) you won't have any trouble, and won't need the Mopar tool.

ALWAYS RE-PACK BOTH BEARINGS BEFORE REASSEMBLY and RE SEAL THE AXLE SHAFTS.

Slantsixness (Tom)



From: jddrivfour
Sent: 2/21/2005 9:14 PM

Sorry, I do not understand. I even have the official parts manual and it does not show these parts. I took off the nuts and lock washers on what would appear to be the outboard side of the axle. . I cannot identify "cones". The center of the "outer plate" which would be held by these nuts, did not want to separate from the body of the same diameter inboard. I did not see a split line. I did rap on the center of the outboard what I am calling cap. The center has a hole drilled in it like that when centering a hub or bearing puller. Are we talking about the same parts?



From: cooneytunes
Sent: 2/21/2005 11:00 PM

ID4.....you are talking about the rear drums...correct?
You have to remove the axel nuts and axel seal, just as if you were going to remove the axel.....you will need to get new axel seals before replaceing or you will loose all your rear end oil..you will loose some upon removal of drums, but this is normal.

Timmy



From: jddrivfour
Sent: 2/27/2005 1:19 PM

I found the cones but they are really stuck. I have hit sharply in center, nearcone. I then took sharp chisel to catch cone edge- they are only sticking up .020 from surface. I am about ready to try and tap small threads in each one and pullout with screw and slide hammer which will take many hours. Any other hints?



From: denison
Sent: 2/27/2005 5:29 PM

I wouldnt try drilling into the cones. Due to the danger of ruining the threads on the 6 or 8 studs sticking up, it is hard to smack the end of the axle with a sledge hammer very hard. It takes a real hard whack.. I would put the nuts back on the studs to protect the threads -have the nuts even with the end of the studs-, and -with long pliers- hold a solid piece of fat steel rod against the center of the axle shaft, and whack the end of that with a big sledge hammer. I think my sledge has a ten pound head. What you called a -cap- is what I call the axle shaft end flange. It has a centering depression/dimple in its end.
It might not move at all on the first whack or two, and will only spring out a few thousandhs of an inch anyway; But that would be enough to get a screwdriver blade between the hub and the mounting flange of the axle to pry it out the rest of the way. I have a round steel rod 6 inches long 2 inches diameter of heat treated steel, that works pretty well. So will a piston-pin from a truck piston. Machine shops might give the old pins away.
Alternately you can try driving a wedge/chisel into the -joint- where the axle shaft meets the hub. This should drive the axle shaft out slightly, and will also raise a burr on both the axle shaft flange, and the matching surface of the hub. You can remove the burrs with a file before you reassemble. If you dont see the split line, scrap away the paint.
Third technique; using a brass hammer or lead hammer, hit the outer edge of the axle shaft mounting flange at a 45 degree angle to the axle. This shouldnt distort the axle shaft mounting surface at all, but would help to loosen the grip of the little cones on the studs. The cones are not complete circles - they have a notch down the side, so that they cose down and grip the stud tightly when the nuts are tightened. This is to -center- the axle shaft exactly.
When you finally get to where you are pulling the drum off, it wont come easily if your brake shoes were adjusted up close to the drum, due to the unworn lip of the drum surface at the inside of the shoe contact area. You might have to back off the shoe adjusters, or work the drum off with more force. Just before the drum/hub is ready to drop off of the axle, you can put some wooden supports under it, to keep it from dropping onto the seal and deforming it. The drum/hub assembly might weigh 50 pounds.
Liberal use of penetrating oil on the stud/cone area wont hurt either.



From: jddrivfour
Sent: 2/27/2005 11:45 PM

Thanks for the "permission" to hit the axle with a sledge hammer. The cones popped out right away. I did not gather from the manual that a sharp hit might need to be a fairly large one. Good news is the brake shoes look new. (wondering if self adjusters were stuck) Bad new is the outer bearing is so bad there are flat sides and spalling on the rollers. I have pressed in car bearing races before, but these bearings must require a huge press. What do you guys suggest as far as what type of local shop is best ?

I really appreciate the help I have gotten this week.



From: denison
Sent: 2/28/2005 7:47 AM

    On any motorhome old enough to have drum brakes I would ASSUME the self adjusters were stuck, or at least stiff.  I like to clean the threads with comet cleasner, and lube them with either a thin coating of grease, or a liberal coating of graphite powder.   
    I dont think a larger bearing would need a heavier press.  The larger diameter bearing would be a little trickier to press in -evenly-, without getting angled to one side on the way in.  Once fully seated it would still be -true- though.   I would hope that any machine shop with a press -wide- enough to hold the drum would be able to do yours.
     You might want to have the drum/hub assembly degreased while they are at the machine shop.  The same tank that cleans up an engine block would work I suppose.  This will clear out the muck in the grease-slinger passages.
    To be able to remove and replace the seal and bearing races It might be necessary to pull out the grease -slinger- from inside the drum.  It is probably only a light press fit.    I am going to assume the drum is attached to the hub, not an integral casting with it.  The machine shop might want to separate the drum from the hub in order to have better access to pressing the old bearings out and new in.  This involves pressing out or unscrewing the wheel studs, depending on which type of stud you have.  If this happens, it would be easy to buy new wheel studs to go back in.  Places that work on delivery truck wheels should have those studs on hand.   I doubt they would need to remove the smaller studs that held the axle shaft to the hub.
     Im curious whether you could tell you had a bad bearing on the rear axle before you got it apart; and was it by the sound?   Mine had no noise I could hear, and the bearings all looked fine when I last inspected them.  My prior experience with bad truck wheel bearings is on pre-war antiques, where you seldom hear a bad bearing because their top speed is -slow-.   

    Your front brake calipers have pistons inside which only move a few thousandths of an inch from year to year.  Muck builds up in the piston bore.   If you want to forestall sticking disc brakes, you can take the calipers loose, push the pistons out -the service manual shows how to do that- and clean out behind those pistons.  New seal and dust boots sets are relatively cheap.  I understand that new rotors and even rebuilt calipers are much more expensive.   Im sure your brakes get plenty of use in Colorado.



From: jddrivfour
Sent: 2/28/2005 6:48 PM

I never noticed a change in "noise". Not a very quiet motorhome on the road. I have only driven this motorhome 10,000 miles. The bearings were most likely bad when I bought it. I have a very bad vibration right at 64 mph. the amplitude changes with speed dramatically. Seems to be from the rear- steering wheel input unchanged. Found a shop to install bearings.