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  #1 (permalink)  
Old 10-04-2019, 06:48 PM
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Default Drivetrain squeak

Configuration: ERA slabside with Jag rear assembly

Symptom: repeating squeak in time with wheel rotation.

Traits:
- only happens after car has been driven 10+ miles at decent speed
- gets louder/harsher fairly quickly over a ~5min period
- sometimes goes away with further driving
- seems to diminish under moderate to hard acceleration, is loudest at light throttle or deceleration
- still occurs when coasting with transmission in neutral

None of the above rules out a front end issue, but it feels like the sound is coming from the rear half of the car and the sensitivity to power/coasting/decel makes me think it's somewhere in the drivetrain.

Any ideas? Conforms roughly to the symptoms of a wheel bearing issue on a regular car, but the Jag rear is more complex. What should I check or lube?

When it's at its worst, it sounds so obvious I feel like I could jack up the car and find it by hand; but of course it never happens when I have that opportunity.

Bill
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  #2 (permalink)  
Old 10-05-2019, 05:27 AM
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My one experience with wheel bearing noise was on an Audi and it usually grew much louder or only made itself know when cornering. Straight-a-way driving it was quiet. It was also a pretty consistent howl in corners - not intermittent with wheel rotation. Type of bearings may be different however.

Does it stop if you lightly apply the brakes?
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Old 10-05-2019, 07:04 AM
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First, put her up on a lift and do a thorough inspection underneath for anything rubbing somehow. Assuming you don't find anything out of line, then...

Second, take her for a drive until the squeak is nice and obvious, then pull her in to your garage and put her up in the air, with the trans in neutral, and spin all four wheels by hand. Listen and feel for a squeak. If the squeak is periodic, in time with a wheel rotation, then it almost has to be a part that is rotating as well, like a bearing, a u-joint, hubs, rotors, or that is stationary and that has a part rotating around it. But if it comes, and then goes, presumably because of thermal expansion, then it's something that is just barely touching something else -- like a cotter pin that is just barely nicking a rotating part and creating a "squeak" when it does. Situations like that almost always leave witness marks that jump right out at you when you finally stumble across them.
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Old 10-05-2019, 08:11 AM
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Does braking effect the noise?
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Old 10-05-2019, 04:01 PM
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Based on a test drive today, I've got the following new information:

1. Squeak diminishes with braking, but doesn't go away completely.

2. Squeak goes away quickly when the car is driven more slowly or stopped, so really seems like something that heats up with road speed and cools down again quickly. Looks like it's going to be difficult to get the car raised and inspected while it's still manifesting itself.

3. Did an initial inspection for anything rubbing or any witness marks. Nothing obvious like that, but I did find a *very* loose nut attaching the passenger-side inner u-joint to the brake rotor - see photo! Anyone know the torque spec? I doubt this accounts for the squeak but obviously it needs to be remedied immediately.

Bill
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Old 10-05-2019, 04:32 PM
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Once you get that torqued down properly, I recommend Cross Check torque sealant. I've found a few loose bolts over the years and finally put this on all major bolts. Sure makes inspection and detection a lot easier.

Kevin

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Old 10-05-2019, 06:08 PM
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I looked on the web and found this:
Quote:
torque value of 55 ft/lbs for the 4 mounting bolts for the rear disk brake rotors
Seems reasonable - you may want to confirm...
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Old 10-05-2019, 10:02 PM
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I've corroborated the 55 ft-lb figure from a number of other sources, and it's appropriate to the fastener size so I've torqued to that (and checked the others).
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Old 10-05-2019, 10:08 PM
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Make sure you have the proper hardware for the application. If the nuts are nyloc, they will not hold due to the heat generated by the brake and differential. I had nyloc nuts loosen on a cobra with jag rear assembly. I did not experience the noise you have. The rear end became very loose as the nuts backed off. The loose nut may not be the cause of your noise, it is something you need to evaluate and possibly address.
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Old 10-06-2019, 11:05 AM
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I had a persistent squeak that was driving me crazy. I mostly noticed it at low speeds. It didn't matter whether the car was hot or cold. It wasn't as noticeable at higher speeds but probably just because I couldn't hear it over the wind and engine noise. I replaced the inner and outer wheel bearings and that resolved the problem. It's amazing how much more enjoyable the car is to drive when I'm not irritated by an annoying squeak.
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Old 10-06-2019, 01:03 PM
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Quote:
Originally Posted by CJ428CJ View Post
I replaced the inner and outer wheel bearings and that resolved the problem. It's amazing how much more enjoyable the car is to drive when I'm not irritated by an annoying squeak.
The front wheel bearings are a cinch to change out -- they're basically just 1970's Chevrolet stuff. The rears, of course, are more of a PITA -- they're all old Jag stuff.
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Old 10-07-2019, 11:22 AM
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Quote:
The front wheel bearings are a cinch to change out -- they're basically just 1970's Chevrolet stuff. The rears, of course, are more of a PITA -- they're all old Jag stuff.
In my case it was the rear wheel bearings. Definitely a PITA!
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Old 10-08-2019, 10:53 AM
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I haven't driven the car enough since fixing the loose axle nut to see if I still have the sound, but I'm presuming it's unrelated. If it continues, it seems to me there are two classes of possible cause:

1. something rubbing or dragging, i.e. contact with a rotating component where there shouldn't be; and

2. something where rotating contact is intended (i.e. a bearing) that is inadequately lubricated and squeaks when it heats up.

The rear is a brand-new ERA rebuild with 200 miles on it, so I'm ruling out any component wearout until I exhaust all other possibilities.

To pursue (2) further, is there any way short of disassembly to verify adequate lubrication of the wheel bearings? I've read that it's possible to jam grease in through the plugged opening on the hub carrier, but that it's a reach to expect this to reach the bearings in any meaningful way.

Does that hub carrier plug just pop out, or is it destroyed on removal? I'd like at least to take a look. Similarly, I'll be backing out the diff fill plug for a look; it's got fresh Teflon tape but I'd still like to double-check the level.

B
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Old 10-08-2019, 12:36 PM
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Quote:
Originally Posted by fintubi View Post
Does that hub carrier plug just pop out, or is it destroyed on removal?
On the original Jag stuff it pops right out. But the verbiage used in the old Jag service literature was that grease was to be added "sparingly." The outboard braked carriers don't have a plug... so that's as sparingly as it gets.
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Old 10-08-2019, 01:17 PM
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Any chance one of the brake pistons is binding in the caliper and not allowing the brake pad to be pushed back by rotor runout?
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Old 10-08-2019, 05:07 PM
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Quote:
Originally Posted by cycleguy55 View Post
Any chance one of the brake pistons is binding in the caliper and not allowing the brake pad to be pushed back by rotor runout?
Rotor runout should be zero, any runout is NOT what pulls the piston back.

The deformation of the square section caliper bore seal is what brings the piston back. The pads only move in thousands.

If you have runout pushing the pads back, you have brake shudder, and a long brake pedal, severity of either depends on the runout value.

Gary
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Old 10-08-2019, 05:28 PM
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Quote:
To pursue (2) further, is there any way short of disassembly to verify adequate lubrication of the wheel bearings? I've read that it's possible to jam grease in through the plugged opening on the hub carrier, but that it's a reach to expect this to reach the bearings in any meaningful way.
You can add grease to the hub carrier through that hole but it won't get grease down into the wheel roller bearings where it needs to be.

Can you elaborate on the "loose axel nut problem" you had? That may be related.
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Old 10-09-2019, 09:48 AM
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Quote:
Originally Posted by CJ428CJ View Post
Can you elaborate on the "loose axel nut problem" you had? That may be related.
See photo in post #5 on this thread. One of the four nuts securing the passenger-side inner U-joint to the inboard brake rotor was not tightened. Now fixed. I've yet to report as to whether this changed anything, but find it doubtful as the other three had been torqued properly.
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Old 10-09-2019, 11:29 AM
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Quote:
Originally Posted by Gaz64 View Post
Rotor runout should be zero, any runout is NOT what pulls the piston back.

The deformation of the square section caliper bore seal is what brings the piston back. The pads only move in thousands.

If you have runout pushing the pads back, you have brake shudder, and a long brake pedal, severity of either depends on the runout value.

Gary
The runout I'm referring to is normal, and at levels insufficient to be felt in the brake pedal. It's probably the extremely rare brake rotor that has zero runout at any given temperature, and even rarer for zero runout at all temperatures.

For example, here are excerpts from a Factory Service Manual for runout and rotor thickness variations:
Runout limit: 0.035 mm (0.0014 in) or less
Maximum uneven wear (measured at 8 positions): 0.015 mm (0.0006 in)


You'll note the maximum for uneven wear or runout isn't zero. IOW, some runout or rotor thickness variation is acceptable within limits.

While I've found references that would indicate each of us is correct, this would indicate it may be a bit of both: https://auto.howstuffworks.com/auto-...isc-brake2.htm

"the rubber piston seal and any wobble in the rotor may actually pull the pads a small distance away from the rotor"
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Old 10-09-2019, 11:36 AM
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Quote:
Originally Posted by fintubi View Post
Configuration: ERA slabside with Jag rear assembly

Symptom: repeating squeak in time with wheel rotation.

Traits:
- only happens after car has been driven 10+ miles at decent speed
- gets louder/harsher fairly quickly over a ~5min period
- sometimes goes away with further driving
- seems to diminish under moderate to hard acceleration, is loudest at light throttle or deceleration
- still occurs when coasting with transmission in neutral

None of the above rules out a front end issue, but it feels like the sound is coming from the rear half of the car and the sensitivity to power/coasting/decel makes me think it's somewhere in the drivetrain.

Any ideas? Conforms roughly to the symptoms of a wheel bearing issue on a regular car, but the Jag rear is more complex. What should I check or lube?

When it's at its worst, it sounds so obvious I feel like I could jack up the car and find it by hand; but of course it never happens when I have that opportunity.

Bill
You may want to check this out: LOL

https://www.gocomics.com/closetohome/2015/02/03
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