Drum Brake issue...

[Capt. Methane]

'92 W-250 that has been ridden hard and wrecked pretty badly by the previous owner. I recently replaced everything in the rear brakes except the backing plate and the hub. New drums, bearings, slave cylinders, springs, pads, adjusting parts, everything.

The right brake would grab some times and was bad enough that the different level of braking could be felt as the wheel turned which I had attributed to a bad wheel seal but the drum was not only worn out of limits but was worn out of round.

The new installation is doing the same thing while driving. While adjusting the star wheel to set the brakes drag in only evident through about half of the rotation-I believe on the rear shoe-unless I really set the adjustment tight which would be too much-the wheel locks up.

I can't imagine any way the backing plate could be causing it. I guess that one of the new brake drums might have been out of round and the odds are 50-50 that it would go back into the same position...

I pulled the axle out but the asymmetrical drag still existed so it isn't a bent axle...

Anyone have any ideas?

 

[dieselshadow]

Drums are more than likely out of round. This is a lot more common than you might think for new drums.

 

[Capt. Methane]

Drums are more than likely out of round. This is a lot more common than you might think for new drums.

Thanks for the response-

Perhaps I'm over complicating it-partly because everything on this poor old truck has been so badly hammered and the simple answer of putting a bad part back where a even worse part had been seems too easy-but yeah, I can't find a US made brake drum so they probably came from the People's Republic of Contagion so I should be surprised that the dang things are anywhere near round and not visibly elliptical!

Do you think I should have the offending drum ground or should I take the thing back to NAPA and try to exchange it?

 

[dieselshadow]

Thanks for the response-

Perhaps I'm over complicating it-partly because everything on this poor old truck has been so badly abused and the simple answer of putting a bad part back where a even worse part had been seems too easy-but yeah, I can't find a US made brake drum so they probably came from the People's Republic of Contagion so I should be surprised that the dang things are anywhere near round and not visibly elliptical!

Do you think I should have the offending drum ground or should I try to take the thing back to NAPA and try to exchange it?

Personally if they look like a good casting, I’d take them to have them checked and machined to spec. If they look like crap, return them for a different set. That may be easier said than done...

 

[Capt. Methane]

I eyeballed the drums a bit but in the absence of adequate measuring tools and NDT equipment I'll have to rely on someone to do that but I did have a name for someone who turns brake drums. I've done a fair amount of business at that Napa store and there is one of the counter guys that I'm on a first name basis with so maybe I'll have some luck...

Hey, I'm in a hotel in LA right now-is there an earthquake going on? Either that or the rioters or using some heavy weapons out of ear shot!

 

[B.G. Smith]

The drum could be out of round but like you say the odds are high. My guess is if the truck has been wrecked that the hub is bent, put with the wheel on, stand something up next to the tire and rotate wheel, If hub is bent much you should be able to detect it. h

 

[Capt. Methane]

It wasn't perfect but I've set up a pry bar on a 20# propane bottle and checked runout in a couple of places including the flange of the axle-that's why I pulled it and tested for drag with the axle removed...there was a little runout in both directions on the flange but taking the axle out of the system did not change things at all.

For now I'm hoping it is the drum. It bothers me that something new should be fracked up like that but given the nature of many imported from the Far East (PRC in particular) parts and assemblies it shouldn't be much of a surprise.

It looks like I'm going to have to pull the hub and drum back off so perhaps the guy that turns them will be able to tell me for sure where the issue is-he should be able to measure stuff like that.

I'll be back home on the 17th, I'll post what I find out sometime after that...

 

[RWherley]

Your axle shaft is free floating, so it cant affect your wheels or brakes it could be your drum if you are lucky, but also look into the backer plate as sever wear on the stop pins at the top can cause weird things to happen, I had a friend who's top stop pin wore through then broke off causing that wheel to lock up

 

[Capt. Methane]

I know the axle shouldn't cause this problem but there's been so many weird things I've come across on this
truck that I will take a look at anything-besides, it unloaded the drum from the differential so I was better able
to puzzle over the issue.

I'm interested in your idea but I cannot figure out what you are calling "stop pins", there is nothing with that callout
in the parts diagram. Are you referring to the parking brake lever bolt?

#10 in the linked parts diagram. It was rusted in quite solidly so it couldn't have been causing the issue
at first and it's tight now...

Or perhaps #25 pin, Shoe hold down spring? They are new with no appreciable wear in the backing plate

https://www.moparpartsgiant.com/res...DBC02962E23B99B91E4C4B4887268219B0B57F29763F7

https://www.moparpartsgiant.com/par...kes_service/brakes_rear.html?Diagram=000005XG

 

[Capt. Methane]

Thanks for the responses guys...

I got in off the trail last night and spent a good part of the day working on the truck, took the wheel off, pulled the axle back out, pulled the hub and drum and took it to the shop. The guy says "It don't look that bad" but when he started making a pass with the cutter it sounded just like the cycle the brake shoe was scrubbing at!

I don't know that much about the tolerances on brake drums but the guy took almost 0.020 off what should have been a perfect new part! I think it needed another five thou off it actually but at least the rear end doesn't hop and grab when I get on the binders now...

People's Republic of Contagion POS parts! It really ticks me off to try and do a job right (I even ordered the proper wrench to use on the axle nuts instead of using a cold chisel) and then have to do it again because of lousy couldn't care less quality control!

And people wonder why I'll go out of my way to spend twice as much for US Made , shoes, or a pair of jeans...

Simple-a belt loop pulling out the second time a pair of jeans is worn is absolutely unacceptable, when your feet hurt from ill fitting junk shoes you hurt all over and because life is to short to spend a day busted on the side of the road and have to replace a whole rear end because a crappy, sub-standard bearing that a company in a foreign land who can't be sued for damages doesn't care how badly their junk screws up your machine!

 

[RWherley]

Sorry for the delay, glad you got it fixed. I was referring to the #10 part on your break down sheet, my friends truck had the part of backer plate that held that whole assembly on wear through and break off.

 

[Capt. Methane]

No worries, in fact I believe that the left drum either warped with a little heat from use or went out of round after installation as it is scrubbing on one side now. Since I hand tighten the lug nuts and finish with the torque wrench it isn't like some brake rotors that were warping when tire technicians used impact wrenches to tighten them...it wasn't dragging before but it is now!

And some people just don't understand why I despise parts made in the People's Republic of Contagion...

what do they not understand about sub standard quality control of parts that were pure crap to begin with?



I'll bet if there was a Lodge Dutch Oven the right size it wouldn't be any more out of round than those dang drums are and would likely make a better blank for a drum-I have no idea what is going to happen when I get on the freeway-the inside may be ground right but the outside wobbles bad so they have to be out of balance!

Funny you mention that parking brake lever bolt. I had taken the truck to a local shop (one that won't be getting any more business from me!) and the bolts and self locking nuts were rusted together. They no doubt tried to put some kind of power tool on the nuts not quite square and rounded both of them, put the axles back in and called me and told me they couldn't get the brakes apart because of that rusted nut and I needed to take the truck to someone "who could put some heat on them"!

Obviously they mistook me for a completely ignorant maroon with that comment which is why I won't even let them work on a lawn mower anymore...

Yeah, okay, I get it...$50/axle for brakes if you don't need a new drum or rotor-they aren't mechanics who fix things, they are technician parts jerkers doing piecework.

I apologized to the truck for taking her to that place-the local shop that I was familiar with the grumpy old owner/manager who could smell what was broke, well, the old man finally-after 20 years of threats-did actually retire!

I know she's a hammered, rusty old First Gen but dammit, last September when I pulled into the campground towing an Avion trailer my wife was dumbfounded when someone ran over and told me I had the best truck in the whole place...

and since she was the only First Gen there the dude had to be right!