RIGHT DRUM SCORCHING HOT AND LOCKING UP

[CFD244]

Hi Folks

I finally got my '71 Demon (741 8 3/4 3.23) on the road (yay). Everything went smooth......car ran great brakes worked well as I bedded the brand new brake components. After about 40 minutes of driving, I applied the brakes aggressively and my right rear wheel locked up on the dry pavement and the car pulled to the right. As I drove home, I tried a few more times with the same results. Once back on gravel, I tried the brakes and again the right rear wheel locked as I could see the evidence in the gravel.

Once in the shop I manually rolled the car with one of the wheels to get it lined up on the hoist. With the car in the air, the drum was scorching hot, but it still turned with no restriction. I gave it a rap with a hammer and it came right off.

Once off, I found the inside extremely black and dusty (other side was spotless)......I confirmed that everything was installed correctly, including primary and secondary shoe orientation. The wear face on the inside of the drum was shiny.

As I looked (and felt) closer, I found that the axle tube from the backing plate to the bell was also very hot as compare to the other side which was barely warm. Even the bell felt warm.

When I checked the axle end play with a dial indicator I found that I have .007 total (FSM says .008 to .018)

So my question..........Does this sound like a bearing problem or a brake problem? Would an overheated bearing create enough heat to cause the braking action of that corner to react this way? The left side has perfect brake action and temp.

I assumed a brake hanging up originally with the black dust etc.......But why could that wheel rotate with general ease when I tried turning it?

Before I start tearing into it........Any suggestions or thoughts??

BTW......Axle bearings, and seals are new and were greased and adjusted as per the FSM. As well, all brake components are brand new with freshly turned drums @ 10.049 dia.

Thanks FABO

 

[4spdragtop]

That sure is beautiful! Well done Troy!

 

[RAT ROD AL]

did it stay locked up , or release when letting off the pedal ? Maybe it's just needs backed off some ! Don't over think it !

 

[CFD244]

did it stay locked up , or release when letting off the pedal ? Maybe it's just needs backed off some ! Don't over think it !

It releases when I let off the pedal.

 

[CFD244]

That sure is beautiful! Well done Troy!

Thanks Steve....Now if I can only get it to work right

 

[4spdragtop]

Ahhh minor tweaks are inevitable for anyone. Im thinking maybe too tight of bearing? Im spitballing here. When you say "bell" you mean where axle tube goes to diff?

Thanks Steve....Now if I can only get it to work right

 

[RustyRatRod]

Sounds like the brake assembly on the driver's side rear is not working.

 

[Dana67Dart]

I had a devil of a time with my 8 3/4 swap.

I used new brake shoes and cylinders but I reused the drums, which were turned perhaps a bit much.

This resulted in overheating brakes

I left my hubcaps off and did some testing

Thermal temp gauge.

I would drive on a road I could stop on without applying the brakes till I was almost at a stand still. Then got our and checked the center of each axel and the drums.

What I found was the pass side was getting hot and the drives side was not

The axle centers were about the same.

This proved the pas side was dragging.

Re adjusted and same result a few miles of driving later

I ended up putting the old shoes back on as they were warn into the drums. Problem went away.


Coincidentally my rear end builder made the incorrect assumption that the bearings got lubed by the axle grease and did not install the inner seals. Most frustrating part is I supplied photocopies of the entire 8 3/4 section from the FSM.

I got the seals installed and re-lubed the taper bearings and reassembled. During the break in period I kept checking axle temps and they maintained a consistent close to equal temp.

 

[Bewy]

Rust/corrosion in the brake line can act as a one way valve, & hold the brake on. Check the park brake cables & make sure they are releasing fully.

 

[Kendog 170]

I once had a bad brake cylinder have those symptoms. I had put (new) ones in. I wound up rebuilding one of my old ones. I too am just spit balling.

 

[halifaxhops]

Were the new shoes arched to match the drums?

 

[CFD244]

Thinking out loud......If in-sufficient axle endplay, wouldn't both bearings be affected?

I'll back off the shoes a bit and get the wheels moving on the hoist and see how the left and right brakes react.

If there were any restrictions in the lines, I would suspect that it would only be the RR as the other wheels are fine?

Wheel cylinders are new.....I actually downsized them as per @slantsixdan recommendation to avoid premature rear wheel lock up. They have 7/8 or 13/16 cups I believe.

Brakes worked absolutely perfect with no pull or drag for at least 30 minutes of driving......Although, I never checked the temps during this time so I suspect it was climbing during this period.

Shoes were not arched to the drum.

Drum spec is 10.090 discard and I am at 10.049.


If all checks out, I'll road test again with my IR.

 

[halifaxhops]

Arch them here is a cheat. Take some say 120 PSA sandpaper put it inside the surface toward the shoes and put the drum back on. Either have some one lightly run the car on stands and slowly hit the brakes. They will form fit the drums. No one does that any more in a shop. @mobileparts Might know some one. Old school tool used on every brake job in the day.

 

[Murray]

Check self adjuster "star" wheel. They are left and right handed thread. If you have them mixed up, they will loosen the adjustment rather than tighten.

 

[RGAZ]

Not saying you messed up, but it sounds like you assembled the brakes incorrectly. What you mention can happen if the Star wheels are reversed (as noted) or the front and rear shoes are not installed correctly or reversed (unlikely), or if the wrong springs were used in the wrong places (possible) or the parking brake level was not fully released and hanging up.

I would adjust them out so they don't drag, go brake a few times and see if they adjusted a lot tighter, if so then there is something wrong in the adjuster. At the very least post a clear picture of the drivers and passenger side brakes as you assembled them.

I do not think you have a bearing issue at all. You have a brake issue.

Lastly, and here is the loaded question: are the brakes stock or did you upgrade the fronts to discs? If so, we need to have a proportioning valve discussion.

RGAZ

 

[CFD244]

Ruled out a bearing problem.

Everything is installed correctly, and functions as it should.

As the rear wheels spun at 30mph on the hoist for 1/2 hour my thermal imager picked up a heat signature on 1/2 of the drum that slowly grew. Checked the drum and found it to be slightly out of round. Dressed it on my lathe, installed and adjusted the shoes. Will road test later to see if that solved my problem. If not, I will install another set of shoes and give that a whirl. I was going to do what @halifaxhops suggested, but I have no sticky sandpaper at the moment. Shoes are new, but new does not always mean good!

Thanks to those who took the time to offer up suggestions.

 

[halifaxhops]

think about this new shoes are made for a uncut drum. When the drum is cut only the center arch of the shoe will ride on the surface. Thats exactly why every time drums were cut the shoes were matched to ensure friction on the length of both shoes, Just old 70's FYI there if it helps.

 

[oldkimmer]

Troy, can u show us a pic of the brake assembly? Are both shoes against the top pin? Did u put new spring kits in them? Kim

 

[MOPAROFFICIAL]

Hi Folks

I finally got my '71 Demon (741 8 3/4 3.23) on the road (yay). Everything went smooth......car ran great brakes worked well as I bedded the brand new brake components. After about 40 minutes of driving, I applied the brakes aggressively and my right rear wheel locked up on the dry pavement and the car pulled to the right. As I drove home, I tried a few more times with the same results. Once back on gravel, I tried the brakes and again the right rear wheel locked as I could see the evidence in the gravel.

Once in the shop I manually rolled the car with one of the wheels to get it lined up on the hoist. With the car in the air, the drum was scorching hot, but it still turned with no restriction. I gave it a rap with a hammer and it came right off.

Once off, I found the inside extremely black and dusty (other side was spotless)......I confirmed that everything was installed correctly, including primary and secondary shoe orientation. The wear face on the inside of the drum was shiny.

As I looked (and felt) closer, I found that the axle tube from the backing plate to the bell was also very hot as compare to the other side which was barely warm. Even the bell felt warm.

When I checked the axle end play with a dial indicator I found that I have .007 total (FSM says .008 to .018)

So my question..........Does this sound like a bearing problem or a brake problem? Would an overheated bearing create enough heat to cause the braking action of that corner to react this way? The left side has perfect brake action and temp.

I assumed a brake hanging up originally with the black dust etc.......But why could that wheel rotate with general ease when I tried turning it?

Before I start tearing into it........Any suggestions or thoughts??

BTW......Axle bearings, and seals are new and were greased and adjusted as per the FSM. As well, all brake components are brand new with freshly turned drums @ 10.049 dia.

Thanks FABO

View attachment 1716424350

Thats usually caused a bad wheel cyl.

 

[CFD244]

I completely disassembled the pass side and read the service manual "word for word" LOL. The only thing I found was I had the parking brake strut anti rattle spring tab installed on the wrong side of the shoe (service manual says it's different for left and right side. One side it is in front of the web, other side it's behind....go figure).

This time, I adjusted the brakes a little looser and the problem has disappeared.

Thanks for everyone's input.

 

[Dartswinger70]

Sometimes the backing plates develop grooves on the flats that the shoe sits on the shoe will extend and hang up in the groove

and not retract etc. If it happens again take the shoes off and check and lube the flats. Sometimes you can polish and grind the

groove down most times you need a new baking plate. I assume you could put tack weld on there and grind it flat also .