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Odd bearing wear issue along with some rear brake oddities:

captdistraction

GrumpyRacer
1,785
1,328
Phoenix, Az
I've got a couple oddities with my last brake change and fun outing.

The car has a bit of a roar which sounds like a bearing. I can hear the rear diff with the seats down, but it doesn't sound like its pinion or driveshaft-related, moreso an outer axle bearing. I've had the passenger side replaced due to a faulty seal, but I believe its driver side. Yesterday I had the car in the air and in third gear/operating, I couldn't hear anything. Yet when driving on the ground, it definitely has a roar. I've spun the front wheels, but not really hearing much there. Sound is speed dependant, not load or RPM.

I should take it to the dealer, but considering my standing 1:3 success record for powertrain warranty coverage, I may be looking into this one on my own. Anyone have thoughts?

The second oddity is in the rear brake pads. The sets I removed both had canted wear patterns, with both inboard pads having their lower leading edges almost worn to the backing plates (less than 1mm). The opposite side of the pad had 4mm. I regreased and moved the caliper pins, but they showed no signs of bind, and everything else checked out ok. Anyone have thoughts on how/why that could happen? Also for funsies, I measured the rear rotors. With 44k on the clock, and 40+ track sessions, the original rear rotors had 18.4-18.6 mm out of their original 19mm thickness. No odd wear, and 17.4mm is the minimum spec. Its cheap to replace them, but I might use the set I took off as a track set to see/gauge the wear before getting a fresh one.

Pics coming shortly.
 

JScheier

Too Hot for the Boss!
What diff do you have in the car? Worn clutch packs allow the axle to slide in / out under load leading to increased / uneven pad wear. You'll usually first feel it in the pedal (soft as the caliper comes back in).
 

captdistraction

GrumpyRacer
1,785
1,328
Phoenix, Az
factory clutch-pack'ed differential / tlok. (totally forgot to check endplay while it was apart)

I'll call and get a service appointment, and see if the bearing noise/wear is also related. Would be crazy if I could get them to replace the outer bearings and the diffential clutches. No one should hold any breath.
 

JScheier

Too Hot for the Boss!
If you pull an axle, you should be able to check the end bearings pretty easily by sight and feel. It's a PITA, but at a cost of diff fluid, it may be easier than letting the dealer monkeys (no offense) tear it apart. You can also pull the wheels, pull the pads and see how much axle movement you've got as an indicator of your clutch pack life.
 
There are two common errors people can make when changing rear pads, both can effect pad wear and braking in negative ways.

First is having the pistion lined up correctly after turning it back in. The slots need to line up to the little pin that sticks out on the pad backing. Sorry I do not have any pictures of that but let me know if does not make sense.

Second is the pin (circled) that hold the caliper to the bracket, it has washers (sort of) built into them. They have a flat edge along one side. That flat side needs to seat on the flat edge of the caliper. While this may not be as bad as the first problem above it could wear the pads unevenly because the caliper is not lined up correctly.

brake_zps58874364.png
 
Yellowboss -

Not having the slots lined up correctly on the piston so that the pin on the brake pad fits propery, could this cause the rotor and pads to excessively heat up and smoke?
 

steveespo

Lord knows I'm a Voodoo Child
Moderator
3,754
1,229
Exp. Type
Time Attack
Exp. Level
10-20 Years
NY Metro
Also pull the slide pins every other pad change and clean and regrease with high temp bearing grease. The heat from track work causes this grease to sludge up and the calipers stick causeing bad wear patterns and excessive heat.
Steve
 
3,793
3,727
IMO, it would seem to be a bearing since it does it under load, with the brake issue that you describe, I would at least consider checking the straightness of the rear end housing while it was apart. You can bolt some straightedges to the axle flanges and measure them, similar to tow in.
 
If you do easy but quick lane changes, meaning don't just jerk the wheel left and right, a wheel bearing will get quiet then loud depending on the load. It is also going to be the bearing opposite the turn, example, if the noise gets louder on a left to right lane change it will be the right bearing and vice versa.

Pinion bearings generally make noise on acceleration. Don't confuse gear noise for bearing noise. A bearing will growl, a gear will whine.

If you pull the axles you can see the axle bearings. Wipe them down and brake clean all the oil off. After a decent cleaning just rotate the bearing with your finger, it should feel smooth. If not get a new one.

Pad wear issues? It seems like you have covered all the bases with the slides. I disagree with the mushy brake pedal too much endplay theory. The emergency brake is made into the caliper. The piston screws in and out, it cannot be pushed in. If there is too much end play in the axle the brakes can't help but wear out.

Hope all this helps....
 

jneary

Performance Fords
323
0
Norcal
My biggest complaint with the Ford 8.8 is the fact that the outer wheel bearings inner race is the axle itself. Means that the axle is trashed when a bearing fails and must also be replaced. I know that this saved money but!!!??!! Ever since I have owned late model Mustangs, I have been into bearings and axles. My 1995 does have a set of axle saver bearings in it but it is a daily driver, not a race car. Axle savers are bearings that are twice as wide as the original bearings and move the rollers inward by the width of the needles to the unworn area on the axle so that you don't have to replace the axles.

If this is an outer bearing, be prepared to replace the axles too. I wouldn't cheap out either, id replace both axles and both bearings cause sure as the one has failed, the other will be next.

Oh, and you will only hear it under load with the car sitting on the axle. When you pull your axles, it will be obvious which it is because the axle will be gauled on the failing side.

John
 
Shaun12 said:
Yellowboss -

Not having the slots lined up correctly on the piston so that the pin on the brake pad fits propery, could this cause the rotor and pads to excessively heat up and smoke?

Yes, and I believe it could and also it could do the opposite, under certain conditions, one of the pads could fail to make contact with the rotor. Fortunately I have not made or personally seen this mistake myself on a S197. So I can not tell you for certain exactly what will happen however I have seen this on other Fords with similar type screw in calipers. It lead to the problems like constant contact and the heating and smoking follows with very fast and uneven pad wear.

I trust what Blacksheep has to say, he is very knowledgeable and I'm sure he has seen it all working on a race team. However in this case I have to doubt you have a bent axle unless the car was in a wreck, he is thinking about cars that take a ton of abuse driven by guys at the top of their game. I drive my car on track a lot and doubt I would ever come close to bending an axle housing - sorry to disagree Rob, you are thinking way above our heads on this one.

Check to make sure the pads are lined up and seated correctly first. If you are sure (you can post pics here) they are installed correctly then it would be time to check other things like Rob mentioned. In that case I would have an experienced tech check the axle, it could be a warranty issue.

steveespo said:
Also pull the slide pins every other pad change and clean and regrease with high temp bearing grease. The heat from track work causes this grease to sludge up and the calipers stick causeing bad wear patterns and excessive heat.
Steve

Good point Steve, also remember this is a wear part and I had to replace mine since I found very noticeable wear on the pin. Lumpy at Roush came up with a better/stronger pin setup for the S197. I would have changed mine but for the cost of their setup I can replace my OEM pins several times.
 

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