Symptoms of a warped brake drum?

Hey everyone, my dreaded driveline vibrations have returned.

I tried another trip to the dealer, and after a through diagnosis, the dealer mentioned they would have to contact Toyota Canada for further assistance. I'm starting to become convinced that I may have a warped rear brake drum(s)

Symptoms
- Vibration between 40 to 50 mph felt primarily in the seat
- Pulsing sensation when braking between 45 to 20 mph
- Speed range of vibration tends to slightly vary a bit depending on how much and therefore how hot the brakes are
- Feels like the rear is "hopping"

What has been done
- My initial vibrations began at 20000 miles. My dealer replaced the axle shafts.
- Axle shaft replacement at 20000 miles fixed my vibration for about 6 months or 8000 miles

Now 8000 miles later, I'm back at the dealer for similar vibrations and after a lengthy discussion with the technician, he mentioned the following:
- Pinion angles are in spec
- Drive shaft was removed and the truck was driven in 4HI, and the vibration was still there
- Tires are balanced
- No visibly vibration when the rear drive train was spun on the hoist
- Since the pinion angles are okay, the leaf springs are deemed okay
- During the previous winter tire change over, the lug nuts seemed excessively torqued (over 83ft-lbs)

To my knowledge, the only thing that hasn't been checked is the 'roundness' of the brake drum. I seriously doubt my new axle shafts are out of spec within 8000 miles.

Based on my information above, does this sound like a possibly warped drum? The dealership won't check the drum unless instructed by Toyota Canada to do so arrghhhh.

 

If the vibration is only there during braking then it more than likely is the drums. You can go to an independent repair shop and get the drums turned yourself for not a lot of Loons.

 

It could definitely be the drums.

also, what tire size are you running? The rear leaf shackles are known to be weak and can cause similar symptoms. BAMF and Archive garage have some replacement hangers that have corrected similar problems. If it’s the drums, great, If not, then the hangers should be your next fix

 

If you have vibration without brake application, you have other problems.

 

I push the button on the e-brake and keep it pushed. Then apply it softly till the brakes engage to see if it vibrates. Don't do this at low speed. You'll lock up the rear brakes. Also, be careful

 

As others said, if the vibration is there when you're normally driving (not braking), its probably not the brakes. But an easy way to test just the rear brakes would be to use the e-brake when you're on a remote back road.

It is good to know that the vibration persists with the rear driveshaft out of the picture. That should help remove a lot of possible culprits.

You said tires were balanced.. Was that a 'road-force' or just a normal balance? A tire that is not round may balance out fine, but it will still feel like shit on the road. If its bad enough the tech may be able to see the run-out of the tire as it spins on the machine

 

When my rear drums on the tundra became very worn and warped at around 150k, i had my brake pedal pulsing when applied.

 

I had the same issue. I brought my truck to my local dealer and told them it was coming from the rear. They changed the front pads and machined the rotors. Dumb asses. Took it to another dealer. There is a service bulletin that addresses this. They replaced my rear axles and fixed the problem.

 

Is a warped brake drum the same as a "out of round" drum. Would a 'out of round' drum be unbalanced and still cause vibrations without applying the brakes?

While trying to self diagnose possible issues, I switch to my winter rims and tires (which were road force balanced 6 months ago) and the vibration was still there, if not a tad worse.

 

Unfortunately my vibrations came back 6 months after my axle shafts were replaced.

 

Back in the the day toyota had a service bulletin like that on the tundra for rear drum pulsing, also one to upgrade to a finer tooth brake cylinder adjuster.

 

I wouldn't think so, but Im not sure. So your saying that you feel one vibration while driving without touching the brakes, and another vibration (pulsing) when hitting the brakes?

 

Correct. I get a pulsing sensation from the rear while braking (don't feel anything in the pedal) and a noticable vibration between 30 to 40mph (wheel balance, and the driveline has been ruled out)

 

How do you know its the rear brakes?

 

It's just a hunch, and I figure I'd ask here before replacing my drums. But I think they are because:
-pulsing sensation while braking
-driveline angles and leaf springs were checked and confirmed okay
- wheel balance is ruled out
- axle shafts replaced 8000 miles ago
- vibration is worse in the morning with cold brakes
- the speed range the vibration tends to occur seems to vary slightly with brake temperature
-the vibration is felt in the seat

 

Did you try my suggestion of using the e-brake to slow down? (do this on a rural road with little traffic..)

The e-brake uses a cable to actuate the rear drums only. Takes the front brakes completely out of the picture

 

Yes, I could feel it, but it was very slight tbh.

 

I guess I'm not 100% sure how much of that pulsing would transfer back to the pedal through a cable vs through the hydraulics of the main service brakes..

I suppose you could always take the drums off and take them to a local machine shop. Have them chuck them up and indicate on the inner surface, see if theres any run-out or warping.. Not sure if Tacoma drums are thick enough to resurface or not. Ive never done it

 

No worries! Thanks for the help Zack.

 

I'm scheduled for a brake inspection this Friday.

I've noticed the vibration changes with brake temperature. There is very little vibration while my brakes are still cold (while on my way to work) and after spending sometime in "stop and go" traffic with repeated brake applications, the vibration in the rear becomes signifiantly more noticeable (and more so when braking)

Definitely seems like a warped drum. If my drums are warped, is that something that's usually warrantable?