Engine/Transmission (1994 - 1998) Rear Brakes Still Grabbing

[TSeran]

I just installed new drums, shoes and wheel cylinders on my 1995 3500 dually and still have some "grabbing".

Everything was cleaned, anti-seize on all recommended spots, and adjusted to where the drums just fit over the shoes and drag slightly. I also bled the lines until new clear brake fluid was visible at the wheel cylinder. I also did the automatic adjustment routine by backing up, stopping, then going forward and stopping about 4 times.

Prior to this post but after replacing the parts I had serious grabbing, like going over bumps, so I opened them up again, cleaned everything really nice, emory-clothed the drums and reassembled everything. This improved the braking smoothness, but the grabbing is still there. If I use the emergency brake only I can feel the brakes still "grabbing" some.

The front brakes have new calipers, shoes and turned rotors and seem to operate very smoothly. It almost feels like the back brakes are doing all the work.

Any suggestions?

 

[hsmith]

Most of us have the opposite problem. Usually the front do most of the work. Sometimes, new drums are not perfect and can be out of round. I can't see the hydraulics, dump valve, etc. being the culprit, but I refuse to be surprised any more.

 

[surfbeetle]

Take a large caliper or some other sort of measuring device and check to make sure that the drums are not out of round. Even though they're new, it's still possible that they are not perfectly round. You may need to have them turned.

 

[SRath]

You said you cleaned everything. I take it that was with spray brake cleaner? Did you have any signs of a leaking wheel seal before? Look very closely for any oil spots on your shoes or drums when you disassemble (again). It doesn't take much oil to cause grabby brakes. Oily fingerprints are enough, much less oil leaks.



Out of curiosity: Were both of your brake assemblies put together at the factory (and reassembled) with the short shoe in the front?



Mine had never been touched to my knowledge (I asked the original owner, too), though I was the second owner, and considering the low miles (80K) and the fact the previous owner never towed or hauled loads very often, was surprised to be having rear brake problems.



Upon disassembly, I found the short shoe in front on one side and on the rear on the other side. All the shoes had plenty of lining still. I had never seen shoes installed that way before and I put them back together with new shoes I had already bought and put the short (leading) ones in the front on both sides like I have always done. My rear brake problems ended.



What is confusing and causes me some wonder is the fact that Dodge parking brake cables enter each drum from the opposite direction and the short shoe was installed according to how those cables entered the drum, though the operation of the parking brake does not depend upon that.



I have always wondered if they intended, for some reason I don't understand, the rear brakes to be mirror-image, like I found them, or if it was just a screw-up. For me, I went with proper dynamic brake function being most important, which requires the short shoe in the front on both sides. I have never had any more problems with the brakes themselves and now have 150K on the truck.

 

[TSeran]

Great minds think alike... ... I just wish I was one of them. I visited the machine shop today to have a broken bolt extracted and discussed the brake issue with the machinist. He too suggested bringing the drums in and he would turn them for free. So as soon as he extracts the bolt and the Subaru is back on the road I'll ferry the drums to him and let y'all know what occurs.

There was no visible leakage when I replaced the brake components, or during the second inspection, and I was careful to never touch the shoes with greasy gloves.

The parts counterman wanted to sell me a $191 part that attaches to the master cylinder saying that it controlled the amount of braking to the front and rear brakes. What's up with that? Made sense, but the machine shop was still clearly the first line of attack.

As for the shorter shoe in the front, I vaguely remember that all four were the same when I installed them, but I will check when I bring the drums in for inspection/correction.

More to come after a quick trip to Texas. Thanks a bunch for all the great input and advice. I'll try it all and report back.

 

[SRath]

"As for the shorter shoe in the front, I vaguely remember that all four were the same when I installed them, but I will check when I bring the drums in for inspection/correction. "



The metal part of the shoes will look the same, but you should see two with longer lining on them.



Some shops will slightly bevel or grind the leading edge of the shoe to supposedly promote smoother contact with the drum. Some shoes come already beveled. If the leading edge hits first, I can see where it might cause the shoes to "kick" and be grabby. Some shops are also very picky about not only making sure the drums are perfectly round, but will also make sure the arc of the shoes matches them for full, even contact. Again, it is easy to see where intermittent contact could cause grabbing.

 

[fortunate1]

Having the same problem as TSeran. My left wheel cylinder blew out recently, so I replaced both rears with the chevy 3500 ones. Big difference in stopping power. Also replaced both sets of shoes and cleaned the drums well. The drums are fairly new & in great shape. However, the right rear really grabs and even locks up slowing down from slow speeds. The left one doesn't do this. The right one also squeals a bit when braking at slow (parking lot/driveway) speeds.

I checked, and the short shoe is toward the front. What gives? Should I loosen the adjuster some? Any help appreciated. I've never had squeaky/grabby brakes before. I may try the bevel trick to see if that helps.

 

[SRath]

One other thought came to mind and it may be way out there, but how is your wheel bearing adjustment?



The shoes are fixed to the stationary backing plate. The drums "float" on the bearings on the axle tube. If there were too much wheel bearing play, I wonder if the shoes could be contacting the ridge inside a used drum or even engaging with the drum riding less-than-true (slightly cocked or slightly wobbly)?



Just a thought. I really hope you guys can get these working right...



[On mine, the driver's side had the long shoe in front and the passenger side had the short shoe in front before I changed brakes and bearings and seals. ]

 

[tgordon]

May be this is only on the 2500's, but there is a proportioning valve to control the bias front to rear for the brakes. When there is more load on the rear more fluid is sent there than with no load so the wheels will do more braking. I do not know if this is so on the 3500's, but is a simple thought, I don't even know where to tell you to look for this valve, I just remember hearing about others who travel loaded all the time removing it. This would only be if both of the wheels lock-up, if only one locks then I would look at differances between the two sides.



fortunate1, did you replace both cylinders, if not I would guess that is where your problem lies.



Troy

 

[TSeran]

I brought the drums in today and had them turned. Tomorrow morning I leave Colorado for Texas. I'll let you know what I learn.

Also, when I removed the drums today the shoes were tight against the drum so I know the adjusters are working (I adjusted them 6 times).

Still haven't looked for the short shoe in front, but will in the am.

 

[fortunate1]

Not sure if TSeran ever got his brakes to work properly, but my right rear still sqeaks, grabs, and will even lock-up if I brake hard at slow speeds. Is this a bleed issue or a "mechanical" issue? The shoes are new (bevelled the edges), and the drums are fairly new on both rear brakes. The left rear doesn't do this. Help!