The Rear wheel seal was leaking on my MC-8. I backed the Bus in the shop on 3” by 12” timbers placed behind the drives and tags to give sufficient height and blocked the wheels.  I backed the slack adjuster off so it would not lock the brake when the air bled off. I blocked up, under the frame between the wheels on both sides to prevent settling from air bag leakage, I put a jack under the beam supporting the axle housing.  The axle came out after a couple of light licks to the center with a sledgehammer. The cone washers can be hard to get loose.  There are threaded holes in the axle to screw bolts into, forcing the axle out if it sticks.  With the wheel jacked up clear, I removed the 3 inch block from under the drive wheel, and inserted the pallet jack. I removed the wheel nuts and outer bearing, and slide the wheel out with the pallet jack. I had to use an impact screwdriver to remove the flat head screws in the seal retainer. The bearing races showed some signs of pits, bearings looked pretty good, but I decided to replace all.  It was about $150 at Allied bearing for the four pieces.   The seal is a two-piece that turns inside of its self, and seals onto a seal surface on the axle.
The seal surface on the axle had some gouges in it, so I decided to try to get it too. I removed the brake shoes to clean of oil. The strap holding the brakes in place with two nuts, also has cone washer. I had to pound it a little to get it free.  After brake removal, I notice the S cam had a lot of slop.
There had been a couple of headed bolts used on the axle instead of studs, and without cone washers. I had not been able to get these at the truck supply.   As it is an 80 mile drive  to the City, I called a Charter &  Bus Repair company to see if he had the proper seal and parts, and got assurance  he did. I Went by Allied and got the bearing, and on  to the Bus Company. I was pleasantly surprised by the helpfulness of the owner, considering his very active business.
He did not have the seal surface for the axle, and said it would take several day to get it from Universal Coach.  He also informed me that if the wheel gets so bad a seal will not hold, there is a seal method that seals the oil from entering the hub from the axle tubing, and you just grease the bearing. He said the big disadvantage to a greased bearing in the rear or front, is the required repacking ever 30k mile. He did have the seal, studs, cone washers, axle gasket and seal retainer gasket too. I ask him about the slack in the S cam, and he showed me the two brass bushing for it. There is a seal on both ends, to retain grease. He had one seal, but was not sure if it was for the drive axle or the tag. The brass bushings were about $3.98 each, and the seal was a whopping 68 cents.
I decided to clean the seal surface instead of ordering a new one. I used several feet of emery cloth to cleaning the axle seal surface. I did not get it perfect, but it is not really that big a deal to pull the wheel again if it does not seal.

I marked the spline on the slack adjuster, and removed the snap ring, and disconnected the DD3 rod to the adjuster. The slack adjuster and washer came off the back, and the S cam slide out the front.  I slide the S cam back in at a tilt to come in contact with the back bushing, and tapped it with a hammer, easily removing the back bushing and seal. I then inserted the S cam in the back and forced the front seal and bearing out too. The bushings did not look as bad as I had thought. They are Very thick bushings, probably a ¼” thick new.  The S Cam seal I had bought was not the right one for the main axle. I have listed the correct number with the parts list. I also noticed the remote grease hose to the bushing was torn into. I washed the parts up and went into my local Auto part to try to get the seal and the hose. Napa didn’t have the seal but could order for next day. I have learned to ask the price, and I am glad I did. The seal was $4.68, and I would need two. I am not cheap, but I decide I could make the old seal work well enough.   The Bus Guy had told me he usually is able to reuse them, and they are not of great importance. Of course I could not get a hose with a twist fitting on one end, so I chose a brake line, and a fitting to convert one end to a pipe thread.  I shaped the Brake line with a tubing bender. I think it will actually work better that the flexible hose.
The outside S cam bushing was easy to get in, but the back was a little harder.  With a piece of all thread, and a washer of the right size I got it in place.  After the Bushing is in, there is a recess for the grease seal. The S cam felt good and snug now. The bus Guy had told me the S cam might have some wear on it, and if much should be built up or replaced. He said new it was about $100. The cam did have some wear, but very slight. I decided to turn it 180Deg. to give it a new surface on the torque point. Now to make the seals work. I cleaned the old seal out and was able to put an O ring in the center.  Instead of putting the seal in the recess with the bushing, I  slide the front seal all the way down on  the Cam  and then put the Scam back into place for the final installation. With a couple of taps of the hammer on the end of the S can, the seal went into place. I carefully fitted the back seal on, and slide it to start point, and with a small hammer taped it into place also. The shim washers were slide on and then the slack adjuster. A snap ring holds it in place.

With the new bearing oiled and new seal in place, I slide the wheel on with the pallet jack. I tightened the nut with a large pair of channel lock pliers, and a bar for torque, while turning the wheel.  The book says to tighten to bind, and back off 1/8 turn. It does take some pressure to seat the seal. After replacing the axle,  I removed the plug on the end of the axle, and filled  the hub with 140 gear grease. I also toped off the  rear end with the same 140. I started the bus to get air pressure, released the parking brake and adjusted the slack adjuster.
After a 100 mile run, there is no sign of leak.
 

 

 
 Mallie Lennon / Eufaula, OK
MC-8

 
Back to Main Page