Educate Me on Air Brakes

[alskdjfhg]

1998 F800 digger derrick truck has a pretty bad brake squeal, I think it's the left rear. The bottom shoe is worn down to about 1/4", the other shoes on the rest of the truck about 1/2" thick.

Took the tires and drum off to get a better look, and the wear is uneven, the top shoe isn't as worn as the bottom and is about equal in thickness to the others on the truck. Is this Normal?

I noticed that the shaft and bracket that anchors the brake chamber, slack adjuster, and S cam shaft to the back of the wheel, moved considerably when I was caging the spring brake. Could that be the cause of my uneven wear?

Does that wobble mean that I have to replace the S cam bushings.

Also this brake is missing the shroud on the back side of the wheel that helps keeps road dirt/crud out, and when I took the drum off a very healthy amount of crud fell out. Could that contribute to the uneven wear?

Also where do you guys get brake parts? I'd imagine that these would be generic parts, just wondering if there is someone cheaper than Ford, they are pretty proud of their parts.

Should I do both brakes on the rear axle so they are matched?

As usual thanks for any and all help.

 

[walkerv]

There are 4 bolts that hold the s- cam tube to the brake anchor bracket , that s-cam tube itself should not move around . uneven shoe wear as you are describing is due to worn out s-cam and bushings, it is advisable to rebuild both sides at the same time and replace the shoes and drums. after markets sources for brake parts would be truck pro or fleetpride. 1/4 inch is the dot limit for brake lining thickness on shoes .on our garbage trucks we actually take all the backing plates off so we can measure and inspect the brakes easier and the crud falls out not really an issue for you that part would be your preference .

 

[alskdjfhg]

Thanks, I measured and I've got about .060 wobble at the S cam bushings, looks like they are toast for sure.

How long is the normal service life for shoes and all brake related stuff? This truck only as 80,000 miles, but the folks I got it from didn't seem to be all that big on maintenance.

Also when I was chasing another air leak I found a 4th tank, a small one at the end of the truck inside the frame. The tank has a pin hole leak (second one I've found of this truck), Ford doesn't have one to replace it and due to where it is located, a replacement would have to be the exact same size.

What I'm wondering is would that tank be for trailer? I thought trailers carried their own tanks, but not sure. If the tank is for a trailer I'm wondering if I can just cap the line so I don't have to mess with replacing it right now.

Since Ford doesn't have the exact same tank (and from the Googling I did, it's not a common size). And since there is zero clearance where the tank is, to fix it, I would just get a generic air tank that's larger and move where the tank bolts to the truck.

But I don't want to mess with doing that right now as I don't even have an air braked trailer yet.

 

[ohiofleet]

yes it needs bushings

 

[walkerv]

Life of brake components all depends on the application and the driver. I have trucks that have brakes last a year and some that only last3 months. Place like truck pro or fleetpride should be able to help you with that air tank too you will need to measure it. If that tank was added don't disable it was installed for a reason , however they built the truck it must have needed more volume for something.

 

[lantraxco]

Bottom shoe wearing can be also caused by the shoe sticking on it's anchor pin if it's the full pin style, and/or a weak return spring, lack of grease for the S-cam, broken return spring in the air can, etc.

 

[fixou812]

Take a picture of the air tank etc. Then visit a truck shop that specializes in suspension brakes and alignment.
They stock alot of parts and should have what you need at a very competitive price.

 

[repowerguy]

This isn't a purge tank for a air dryer is it?

 

[alskdjfhg]

I took the drums and shoes to the local Napa at the farm, they had some drums and pads that should work. Cost $400 for two sets of shoes, two drums, jar of anti-seize, two axle seals and a can or brake cleaner. They didn't have the S cam or S cam bushings unfortunately.

I'm sure they weren't the cheapest, but they've gotten me out of jams before so I didn't mind it too bad. And they've never been jerks like most industrial supply/truck parts places normally are.

Any tips about freeing the tapered washers on the axle hub so I can get the S cam out? They are really seized on there, afraid I just need to make a puller.

I'm sure I can replace the air tank. Worse comes to worse I'll just get a larger one and move where the tank is located on the truck to somewhere I've got room.

 

[Shimmy1]

$400 sounds just right. You shouldn't have to pull the hub to get the s-cam out. There should be some bolts on the back side of the wheel that hold the cam housing. Of course, if you have spokes, disregard these comments. :cool2

 

[walkerv]

Loosen the axle nuts and hit center of axle shaft with a sledge. If you end up having to actually pull the hub off. Check the cones after a couple hit to see if any are loose using a pair of pliers

 

[clintm]

To get the axles out smack it with about a 2 pound hammer right in the center of the axle end cap a couple of times. It should pop out enough so you can pull the washers off

 

[alskdjfhg]

Many hammers of various sizes were involved as was penetration oil, large screw drivers, pry bars and expletives.

Last thing I tired was a 5 lb sledge and whacked the center of the hard pretty hard several times stright om. No budging. They are on there TIGHT.

$400 sounds just right. You shouldn't have to pull the hub to get the s-cam out. There should be some bolts on the back side of the wheel that hold the cam housing. Of course, if you have spokes, disregard these comments. :cool2

I'll have to look again, but I think that I'll have to pull the S cam out through the spider and in order to do that the hub has to move out of the way.

 

[alskdjfhg]

This is what were dealing with.

 

[lantraxco]

From an old Hyster manual: "Rap the center of the axle head smartly with a 20 lb hammer" ya gotta get some bounce to move them.

Then I would use visegrips to kinda thread them out a ways and a thin screwdriver to drive in the slot to open up the cone washers.

(Edit) Just looked at your pictures, you might as well pull the slack adjuster and air can mount off, it's four bolts and a snap ring, then you can probably angle the S-cam enough to get it past the hub flange.

 

[Shimmy1]

Looks just like my International axles. If you pull the brake chamber, slack adjuster, and the s-cam tube, you will be able to tip the cam past the hub.

 

[alskdjfhg]

Cool, that makes life easier.

Hopefully tomorrow I can get that done and be ready to look for parts Monday.

 

[Shimmy1]

Cool, that makes life easier.

Hopefully tomorrow I can get that done and be ready to look for parts Monday.

You are probably going to struggle with the slacks. They like to rust onto the cam. Slacks are cheap. If they don't come off easily, chances are you'll wreck them trying to pull them off. I've only had a few I couldn't get off, and since I was changing cams and switching to automatic slacks anyway, I just cut the old ones to get them apart. I'm guessing you're going to need cams so don't worry too much about it. A thin cutoff wheel and carefully cut the cam end off and the shaft and slack will slide out the tube. If you are crafty, I'm sure you could source a bushing that you could use like an arbor press to slide over the shaft that could fit against the spline coupler in the slack to press the cam out.

 

[alskdjfhg]

Dosent look like I can get the S cam shaft out without cutting it. But cutting it seems like only a short term solution as then I won't be able to get the new one in.

So looks like getting the hub of is the next step.

Also, one of the bolts that hold the S cam tube to the back of the spider broke off with only about 10 lbs of force. Was able to get the other 3 out, but 2 are very obviously bent and the 3rd isn't bent as visibly.

Since that bolt broke off in the spider, looks like I get now also take the spider out and drill out the broken bolt with the mill.

 

[alskdjfhg]

https://youtu.be/IF1LYBKXX6o

Would that tool help or am I over thinking it and I just need a BFH? Thinking about copying the design and making one.

I missed a hammer blow a whacked one of the hub bolts, even though I put the nuts on the studs just in case I hit one, I still kinda chowdered the end of the stud.

I've been whailing on the hub pretty hard and long, its not budged. It looks like it's pretty rusted in there.