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Discussion Starter #1
My yukon has had a pulsation in the brakes since I bought it 5 years ago. Felt like a warped rotor, but I replaced all the rotors and it still didn't go away. I knew it wasn't ABS or wheel bearings (wheels surely would've fallen off in the past 80k miles if it was that) but i couldn't find any other explanations on the internet or think of any myself. I finally got fed up and put a dial indicator on the brake rotors. Both rear rotors read .008" of runout near the outer edges of the rotors (both sides). So, warped rotors, right? No. I removed the rotors, indexed them by 60 deg to the next set of holes, and the high spot did not move with the rotors. It corresponded to a high spot on the hub. I tried all 6 positions of the rotors on the hubs, and it did not matter how the disk was indexed, the high spot always corresponded to the same stud of the hub. I thought maybe some trash or something was between the hubs and the rotors, so I wirewheeled both mating faces real good and checked them over, clean as a whistle, this changed nothing. I ended up putting shims of aluminum foil between the hubs and rotors to get them to run true, and now the pulsation is gone. I suppose I could have taken it to a brake shop and had the rotors lathe-turned on the vehicle, but if a rotor ever got removed and put back on in a different orientation then the problem would be doubly worse than it was before.

Question #1 - is there any reason that my aluminum foil shims are a dangerously stupid idea?

Question #2 - how could this have happened? The only idea I can come up with is the vehicle was hit from the side, bending both hubs slightly, but there is nothing on the accident history and I cannot find any evidence of body work at all.
 

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I've never heard of turning rotors while mounted on a vehicle.

In my opinion, the "shims" will fall out and you will have a loose wheel.

Edit:
How do you tighten the wheel lugs, are you using a torque wrench?
 

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Discussion Starter #3
I've never heard of turning rotors while mounted on a vehicle.

In my opinion, the "shims" will fall out and you will have a loose wheel.

Edit:
How do you tighten the wheel lugs, are you using a torque wrench?
167427

I don't think the shims will fall out. I use a ugga dugga.

 

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2000 Silverado Z71 4x4 5.3L 460k+ miles w/ GM rebuilt motor and trans
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I wonder if you could do that to the face of the axle...but is it just a Band-Aid?

I'd be curious to know if your axles are bent inside from overloading and hitting a speed bump or something. Seems more likely than being hit in the side and BOTH sides deforming the same.
 

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Discussion Starter #5
I'd be curious to know if your axles are bent inside from overloading and hitting a speed bump or something. Seems more likely than being hit in the side and BOTH sides deforming the same.
Huh, you know what I think you're right. That does make a lot more sense. And if that's the case then the axles have been "cork-screwing" (I'm sure there's a better description) inside the bearings this whole time. Surprised I haven't had more issues than the brake pulsation.

I wonder if you could do that to the face of the axle...but is it just a Band-Aid?
I bet it could be done, in some sort of contrived way. I conjure cringy images of an angle grinder mounted on an arm, contacting a wheel hub with the vehicle running 60mph on jack stands with the wheels off. Unless there's a more legit method that I don't know about, I think the aluminum foil shims are preferable. "You never know until you try" but I'll pass on that one.
 

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Discussion Starter #6
I'd be curious to know if your axles are bent inside from overloading and hitting a speed bump or something. Seems more likely than being hit in the side and BOTH sides deforming the same.
I think I can test for that. I'll put the indicator on the O.D. of the hub instead of the face of the rotor, (can't get to the face of the hub, for the studs being in the way) and if the O.D. is as jacked as the face, then it means the shaft is bent. At least I think thats logical.
 

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2000 Silverado Z71 4x4 5.3L 460k+ miles w/ GM rebuilt motor and trans
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Vertical variance at the outside edge of the axle hub face will be affected by a bent hub face, even if the shaft is not bent.

Honestly, the best check is going to be pull the axle and check for vertical variance between the 2 bearing points. A lot more work, but a definite answer.
 

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Pulling the axles would also allow you to check the hub faces are perpendicular to the axle shaft.
 

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Discussion Starter #9
Yeah I agree, but I don't see myself going to the trouble just to satisfy my curiosity. I've put 80k miles on it this way and I'll wager I could put 80k more. If not, then I'll be pulling the axles anyway. I hope the aluminum shims do the trick for the long haul; don't see any reason they won't, but if I'm wrong then I'll cross that bridge when I come to it.
 

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2000 Silverado Z71 4x4 5.3L 460k+ miles w/ GM rebuilt motor and trans
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The only thing it should do now with the "vertical" tires is hop up and down minimally as the axle wobbles. Should be...fine?
 

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The aluminum sandwiched in between the steel should create an electrical charge and turn to dust..... keep those wheels torqued.

Al
 

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Discussion Starter #12
The aluminum sandwiched in between the steel should create an electrical charge and turn to dust..... keep those wheels torqued.

Al
Ah yeah, galvanic corrosion. The wheels are already aluminum, not sure if that makes a difference. But they're probably covered in some kind of protective oxide or anodizing, although they appear to be bare aluminum. Maybe steel shims would be better? Or brass?
 

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Discussion Starter #13
The only thing it should do now with the "vertical" tires is hop up and down minimally as the axle wobbles. Should be...fine?
I didnt feel any wobble driving it this morning. I guess that doesn't mean much though; I've seen folks driving down the road with one tire bouncing 3" off the highway and seeming totally unaware of it.
 

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2000 Silverado Z71 4x4 5.3L 460k+ miles w/ GM rebuilt motor and trans
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I didnt feel any wobble driving it this morning. I guess that doesn't mean much though; I've seen folks driving down the road with one tire bouncing 3" off the highway and seeming totally unaware of it.
Saw that yesterday on the back of an Explorer. That tire was JUMPIN' at 65mph, but the body of the truck was basically motionless. With the difference you have, it would be almost imperceptible even to people watching your tires, in my opinion.
 

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I also suggest checking the axles - -they might be bent. I have heard of an instance where a truck being transported had chain binders over the rear axle so tight it bent them slightly.
 

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Depending on your budget, get another axle from a junk yard or replace it with a new one. Are your sure it's not the wheel?
If you stay with your bandaid, smear on some antI-seize paste. Do not over do it and not on the lugs.

Is it OK to put anti seize on lug nuts?
But experts tell us not to use any lubricant, including anti-seize compound, on wheelstuds or nuts. The tech folks at Tire Rack state: "Torque specifications are for dry threads only. The fastener threads should be free of oil, dirt, grit, corrosion, etc. It is important NOT to lubricate hardware threads or seats.May 29, 2019
 

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Discussion Starter #17
I don't like publicly confessing my failures, but in the interest of saving anyone else the same fate I'll tell you that aluminum foil shims between hub and brake disc is NOT the answer for this specific problem, whatever it is (I'm thinking bent axle shafts).

At first, it seemed to have worked. 95% of the pulsation was gone from the brakes. Over the past 5k miles it slowly came back, worse and worse, until it was far worse than it had ever been before the shims. It started to become a problem even when not braking. I would hear a "wa wa wa" from my tires as I roll down the highway and sometimes it felt like I was on a bumpy road even when I wasn't.

I had put on new tires around the same time I installed the shims. I noticed last week that my rear tires look way too worn to be that new. I decided to remove the shims today and I checked my tread. On the front I still have 90%. On the rear passenger side I have 30%-60%, depending on where I measure, it isn't evenly distributed. Rear driver's side is 50%-75%.

I don't 100% know what the problem is, I don't know what the solution is, and I don't have the slightest idea how my shims seemed to work at first and then turned out to make the problem worse. All I know is that putting shims between the hub and disc is a great way to trash a brand new set of tires. So don't do it. It isn't clever. It's stupid.
 

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The new tires were soft and full of rubber. As the wobble started it aggravated the tire and you may have broken a belt or the belt has separated due to heat.

I have more than once had new tires that would cause a wobble. It was just poor quality during the molding process. One time I had a 1992 Saturn and never had tire or shake problems. Then one day after getting new tires occasionally I would feel the shake. The tire shop bent over backwards and even did a spin balance with the wheel still on the vehicle. That didn't fix it so they replaced two tires. That didn't do it. About three years later with a new set tires, the wobble went away.
 

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Discussion Starter #19
Since my tread depth measurements weren't consistent around the circumference of the rear tires, I guessed that meant I had worn some sort of pattern into the tires, and that depending on how I put the wheels back on after removing the shims, that pattern would either add to or cancel out the wackiness of the hub/axle/whatever-it-may-be. I wasn't sure whether I should put the wheels back on exactly as I had taken them off, or index them 180 degrees. I chose to put them back the same way they came off, and I think that was the right call. I barely feel any pulsation, and what little I do feel might just be in my head. I will give this a try for a while and see if it stays gone. If not I think I'll go get a whole new rear end, followed by a set of new tires. I would like to open up that rear end, pull the axle shafts, and see just what the heck is going on with it, but I can't afford the downtine playing amateur forensic investigation on my daily driver.
 

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I'd like to know why I dont have an alert for this thread. I should be subscribed as I replied.

Ya theres no fricken way putting aluminum between 2 pieces of steel would ever last. The wobble is still there and it would act like a ball peen hammer every time the wheel turned. Smashing the aluminum thinner and thinner. Your probably lucky you didnt loose the tire and kill someone.

Take your truck to a mechanic!

Al
 
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