Parking brake drum question

[Kayaker]

I pulled the parking brake drum to check and clean the shoes and noticed this rather deep groove around the hub. I've had this off a couple of times over the last 40 years but don't recall ever seeing that groove. No filings in the transfer case oil and no filings in the drum so I'm hoping the groove is normal and not the result of rubbing on something. All the photos of the drum in my manuals only show the outside of the drum. Anybody know if the groove is supposed to be there?

 

[PWCO70crusier]

I think I took some pictures of mine when I had it off, but I'll have to check when I get home. I'm pretty sure mind didn't have that grove though.

 

[tyama]

Hi, I thought that groove came about 'cause of the seal rubbing against it. It's usually not there when the unit is new. The ones I've seen are a bit more shallow so I'd be wondering what caused it. The smaller ones can be fixed by a speedy sleeve, but I wonder for one that deep if you'd have to weld it. Does the oil leak out from your brake?

Good luck, ty

 

[Fast Eddy]

Not sure I've seen one like that. Seems like it's worn almost through?

One pic from elsewhere on mud:

With a google search I found one that looks like yours on another site (big pic).

http://1.bp.blogspot.com/-YUV7X4WJ4MY/UeNBf8ypN7I/AAAAAAAAAwA/jLcjdKotYrU/s1600/CIMG7250.JPG

 

[handcannon]

Could that be caused by a loose backing plate, or other loose brake parts from sometime in the past?

Don

 

[sggoat]

Blowing the pic up to 400% -it looks like the groove is a wear result. You can see some metal flaking near the bottom. Don't know if the groove is there on a new/original one. Was there anything around this that rode on it?
Here's a pic of the brake from TOYODIY-it doesn't seem to show a groove---

 

[B y r o n]

What do the other parts from inside the drum look like?

At minimum it looks like you need a new drum and whatever was rubbing against the center shaft.

 

[Kayaker]

Well I figured it out; thanks for the feedback. Here are photos of the inside of the parking brake. It's in good shape, no surprises there. After pulling the brake lever with the drum off, it became obvious where the problem was. The internal lever where the cable attaches, is capable of making contact with the hub of the drum (third image) so whenever the brake is engaged and you drive the LC, it acts like a metal lathe. I'd not have guessed that that internal part was hard enough to cut that nearly 3/16 inch deep channel in the drum hub without incurring major damage itself. As you can see from the images, it shows some heat build up and only a small dimple where it made contact.

Image one is the brake adjusted properly but totally released (brake handle in). Image two is the position of the shoes and internal lever with the brake handle in the set position (7 clicks). I found that in the set position, there would have to be a channel in the hub for the brake shoes to make contact with the drum. That's a little surprising given that the shoes are fairly new and still have plenty of liner left. I'm surprised there were no metal filings inside the drum or on top of the shoes. If the channel in the hub wasn't so rust free I'd have guessed that the channel was created some time ago - like the time my daughter drove 20 miles with the parking brake engaged.

At any rate, I'm glad to have found the cause of the groove and that it can be prevented by not driving with the brake set; seems like a good idea.... I think it's time for a new brake drum before mine shears off at the hub next time I go to haul a Jeep out a quagmire. How embarrassing would that be...

 

[DSRTRDR]

the red light on the dash was supposed to warn you when the parking brake is set - don't drive when it's on (although I have managed that a few times myself )

 

[huminajumina]

Wow, that is pretty crazy, I know I've left my brake on for a few hundred feet, & I have seen plenty of posts from other users leaving there brakes on!

 

[Kayaker]

the red light on the dash was supposed to warn you when the parking brake is set - don't drive when it's on (although I have managed that a few times myself )

Believe it or not I spent hours and hours getting that brake warning light to work again. Trouble is, though it's hard to miss at night, during the daytime it's all but useless! Maybe one of those reverse warning beepers would be better......

In my daughter's defense, I had just repaired the parking brake (but not the warning light) which hadn't worked in years and she didn't even know it had one. She knew she really had to give it the gas to make it move but didn't have any idea why it was so sluggish. It was after it started smoking and smelling really bad that she decided to turn around and head back home. By then, the parking brake was toast (and apparently the hub on the drum as well). You should have seen the look on her face when I told her it had a parking brake.

 

[DSRTRDR]

it's always the women

 

[Weber Sarge]

Mine must be exceptional or adjusted too tight , it won't move without slipping or burning the clutch ...

Trust me , men do worse boneheaded things , like dragging semi fuel tanks until they run out of diesel...
Sarge

 

[DSRTRDR]

Mine must be exceptional or adjusted too tight , it won't move without slipping or burning the clutch ...

on pavement, my truck didn't move with the parking brake set, either, but after a half day of wheeling where the parking brake got greased up real nice from the tranny/transfer case leaks , it didn't hold so well anymore

now that the H55 is in, and the parking brakes are on the rear axle, this will hopefully be a problem of my past

 

[Weber Sarge]

I really prefer the t-case brake since it has the advantage of using the gearing in the rear axle as leverage . Rear drum axle parking brakes are rarely ever as strong in holding a vehicle on a hill - my Sami went for one heck of a ride once at the Badlands (no one hurt ) . Lesson learned , that rig got a set of German made ball valves routed into the brake system to actually lock/hold all 4 wheels .
Sarge

 

[DSRTRDR]

I will report back . . .

 

[Kayaker]

Well, I figured since I started this thread, I may as well see it through for anybody that may encounter the same problem in the future. It appears that the scored hub on the brake drum was caused by the internal lever rubbing against the hub when the brake was set. I imagine that the spring kept the tension on the lever which contributed to the depth of the scoring. (See photo 1)

When I discovered the scored drum hub, there couldn’t have been much more than a fraction of a millimeter of metal left before it would have worn all the way through and started scoring the splines on the output shaft. Good thing I found it when I did.

Before I replaced the brake drum, I figured I better find out how it happened so that I wouldn’t have a repeat performance. When I compared the position of the internal lever when the brake was released to the diagram in the shop manual, it was apparent that the lever was not pointing directly down as it should, but rather was being drawn towards the hub by the brake cable. It turns out that my brake cable was adjusted too tightly. Once I loosened the cable up by adjusting the two nuts on the upper end where it passes through the firewall, the lever relaxed and pointed downward as it is apparently designed to do. Take a look at the photos and you’ll see what I mean.

The two photo series show the position of the brake lever with brake off, then set (8 clicks) and the brake cable at the firewall, engine side. The first series is before I adjusted the cable length – the setting where the lever rubbed on the brake drum hub when set. The second series shows the lever position after I adjusted the cable. Note how much more clearance there is between the output shaft (and consequently the brake drum hub) with the cable adjusted correctly both when the brake is set and when it is released. I should add that the brake shoes in both sets of photos are adjusted correctly, the only difference is the adjustment of the brake cable at the firewall.

So, there you have it. (I sure hope I get used to this new web design.)

 

[Weber Sarge]

I could see if the shoes are worn past a service limit or the cam mechanism in the brake arm is worn it would cause a different arc and having to over-adjust the cable setting - investigated that route ? I'd look at the end of the brake arm , cam face and mounting points for sure .
Sarge

 

[Kayaker]

All the serviceable brake parts were recently replaced so I ruled those options out. It was the diagram in the factory service manual that made me consider the cable adjustment and once I did that, everything fell into place. Learned that there's more to parking brake adjustment than just the drums. Too bad it was a $100 lesson.

 

[Curtice]

Perfect timing for me on this thread. I just took my brake apart last night and....

Good info above. Thanks!