Single tire chirp with downshift

[Christien]

Out for a drive today and noticed my rear passenger side tire started chirping with downshifts. And not "sporty" downshifts, just regular driving, maybe slowing down for a turn in the road. If I double clutch it doesn't happen.

I also noticed a rather strong smell, something I couldn't place. (Not burning oil, tranny fluid, burnt clutch or tire rubber). If I had to describe it, I'd say scrambled eggs, but less sulphur-y. When I got home the engine bay looked totally normal, no leaks anywhere. 20 minutes later, the floor underneath is perfectly dry.

What could this be? The only thing that came to mind is the limited slip - I've only had this car about 4 years, and it's my first experience with LSD.

[pmax]

Are you sure it isn't your fan belt ?

Sulphur smell could be an overcooked battery. Faulty VR will do that.

[Christien]

fan belt is still there, and there was no light on the dash.

[pmax]

Originally Posted by Christien

fan belt is still there, and there was no light on the dash.

How loose is it ?

Don't rely on the lights. Use a voltmeter.

[anglophone1]

Thrust bearing?

[Christien]

Belt tension feels good, about 1/2" deflection. Voltage looks good too, 13.1 with the engine off, 13.75 at idle, 13.9 at 2000rpm (without headlights, a/c or anything), measuring at the battery terminals.

[Canada Kev]

You might have better results measuring the voltage as you're driving, not stationary. When I had a bad VR, volts were good engine off, at idle and 2000-2500 rpm. I only saw it get into the danger zone after I started driving the car - half way down the block it jumped to 16V. I just measured it at the cigarette lighter with a pigtail I made from a 12 volt accessory cord and my meter.

I believe that when the regulator goes bad it'll be high voltage, not low.

[Christien]

I've got a cigarette voltage meter coming today from Amazon. But none of that would explain the tire chirp on the downshift would it? I'm worried there's something going on in the differential, and maybe the smell was related to that.

[Driven97]

If you're going straight, the differential part isn't doing anything. So if you're thinking the diff is essentially momentarily stopping the right rear tire, it doesn't make much sense mechanically. If a diff fully locks, it keeps both rears turning at the same rate, it doesn't stop one side.

Just out of curiosity, have you checked your CV joint bolts? Or, have you jacked the car up and wiggled the tire? Have you turned the RH rear by hand to make sure you don't have a sticking caliper or e-brake mechanism?

[sixbanger]

Maybe it's pulled head studs.

[Christien]

Originally Posted by Driven97

If you're going straight, the differential part isn't doing anything. So if you're thinking the diff is essentially momentarily stopping the right rear tire, it doesn't make much sense mechanically. If a diff fully locks, it keeps both rears turning at the same rate, it doesn't stop one side.

Just out of curiosity, have you checked your CV joint bolts? Or, have you jacked the car up and wiggled the tire? Have you turned the RH rear by hand to make sure you don't have a sticking caliper or e-brake mechanism?

I haven't done any of that, but I will. I know one of the calipers does stick from time to time, and I have the parts to rebuild it (it's on my list for this summer), but would that actually grip the brake disc enough to actually lock the tire up momentarily, and only during a downshift?

Though now that you mention it, I wonder if it was only happening in turns. I'm going to take it for a spin today and test that.

[ClickClickBoom]

Originally Posted by Christien

I haven't done any of that, but I will. I know one of the calipers does stick from time to time, and I have the parts to rebuild it (it's on my list for this summer), but would that actually grip the brake disc enough to actually lock the tire up momentarily, and only during a downshift?

Though now that you mention it, I wonder if it was only happening in turns. I'm going to take it for a spin today and test that.

If its dragging the extra drag could overcome the tires grip.

[Christien]

Even at 60 kmh?

[Quicksilver]

Originally Posted by Christien

Even at 60 kmh?

The emergency brake is assisted by rotation so that could be it but you should see a bunch of heat coming off of it.

[Christien]

Doesn't the e-brake only lock the driver's side wheel?

[aston@ultrasw.c]

Originally Posted by Christien

Doesn't the e-brake only lock the driver's side wheel?

Both sides.

A bit of a weird one.

Some thoughts:

Can you get it to chirp by coming off the power and then going back on without shifting?

The grip of the tire is so great I can not imagine that the sound is really coming from the contact patch.

I'd look at drive shafts, suspension mounting points, engine mounting points etc

Use an IR thermometer to compare temps side to side to see if anything is dragging.

For it to smell, something is getting hot.

[Christien]

Originally Posted by aston@ultrasw.c

Can you get it to chirp by coming off the power and then going back on without shifting?

I don't think it was doing that, but I can't say with 100% certainty.

I'd look at drive shafts, suspension mounting points, engine mounting points etc

Use an IR thermometer to compare temps side to side to see if anything is dragging.

For it to smell, something is getting hot.

I'll look at those, for sure.

[RSTarga]

If double clutching eliminates the problem, could be sticking clutch.

[Christien]

Wouldn't that affect both wheels, not just one?

[anglophone1]

Clutch release bearing - mine made same noise- thought it was the belt.