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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 |
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? |
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. |
Does braking effect the noise?
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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 |
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 https://live.staticflickr.com/65535/...9eec8205_o.jpg |
I looked on the web and found this:
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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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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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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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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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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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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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Can you elaborate on the "loose axel nut problem" you had? That may be related. |
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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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https://www.gocomics.com/closetohome/2015/02/03 |
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