As I understand, 86-88 RX7s, namely the Sport/GTU, GXL, and Turbo II had clutch-type LSDs, and that they are prone to failure.

I've been hearing a howling noise that goes away when the car goes into a left turn at speed. If I go to the right, the sound doesn't go away.

I have checked if the rear bearings are bad and the rear wheels have no play. The sound is definitely NOT coming from the front.

Could it be another bearing on the rear differential?

There's no clicking or grinding, or buzzing, just howling.

 

Jack the car up under the rear shocks, so as the suspension remains normal, start car, put it in gear and see if you hear a noise. Could be tires.
Got my '89TII back at the end of Aug. after having a Mazda reman. engine installed, along with a trans rebuid, and had a rumbling noise from the rear. The car was in the shop 3 months, and I didn't recall such a pronounced noise. Tonight I just jacked the rear up and took it to 50, not a sound....In my case, must be the tires.

 

It's not the tires. This howling noise is metallic-like.

The sound goes away when I go into a left hand curve. It doesn't when I'm going straight or into a right-hand curve.

It also appears to be coming from the rear center of the car, not the sides.

I guess the question I should have asked was: What kind of sound would a clutch-type LSD make when it fails?

 

Check out your CV joints back there. Sounds like your left one may be dry and on its way out.

 

Definitely not something I considered.

Besides a cracked boot and leaking grease, are there any other signs of a failing CV joint that I should be looking for?

 

Sorry, I read howling as a non mettallic sound, which you corrected.
An inner/outer cv joint can be defective without the boot being torn. Just from wear.
This howling, I would think, would be more associated with a wheel bearing going bad.....However you have stated they are ok.

 

i had same problem and it was rear wheel bearing....i haven`t found it by searching for freeplay, i just started replacing parts...

 

But, why does the sound go away when you enter a left curve and not when you're going straight or into a right curve?

I certainly am not going to start tearing into my car and replacing what are probably still good parts to solve what could be a minor (or major) problem; that's not an acceptible solution (nor cheap). Nor is it good troubleshooting.

What I want to do is trace the source of the problem, and replace the bad part(s).

Case in point: My Dad's '96 Millenia had a nagging check engine light, the mechanics just replaced sensors and computers, which didn't solve the problem but left him with a massive repair bill. Just because the code points to a sensor doesn't mean it's a bad sensor or computer, you need to know what caused that sensor to go bad. It's running like a top today with 123000 and counting.

hIGGI, the possibility that it was a bad wheel bearing had also occured to me, so I'll keep that in mind when it comes time to do the work.

Turbonut, I could also be wrong about the wheel bearings. I'm not a trained mechanic, and though I did check, I probably wouldn't know the difference between a worn-out bearing and one that was brand-new :-).

If the CV joints were bad, wouldn't I also hear a clicking sound if I drove the car slowly?

 

A few points on the diff only:

The normal sound of something going wrong with a LSD diff is a chattering sound due to incorrect lubrication. To check to see if your diff is out, do the following steps.
1. Turn off engine and shift the trans into reverse
2. Block front wheels
3. Jack up rear and support rear with jack stands
4. Release parking brake
5. Measure the time it takes to turn the wheel 90degrees while applying the specified torque.
Specified torque: 39 M.m (4.0 m-kg, 29 ft-lb)
Specified time: 4.0 sec. Min.
6. If not as specified, replace the viscous limited slip diff and fill with new specified oil.

Also, check the sides of the diff at the shafts inspect for leaks

Question. Does the sound die when turning left under acceleration ?

 

Possible problems on the noise from the rear axel assy:
-Bent bearing housing
-Bent drive shaft
-Worn or damaged wheel bearing
-Worn drive shaft spine

If it is any of these, then you must replace the problem bearing.

Possible problems from the viscous LSD:
-Insufficient diff oil
-Incorrect oil
-Improperly adj. Ring gear backlash
-Diff oil seal
-Drive pinion bearing
-Worn thrust washer

If it is any of these, then the correct course of action is needed.

 

When a FRONT wheel bearing goes bad and starts to make that howling noise, if it's the left side bearing, turning to the right tends to make the noise go away, and vice-versa for the right front bearing. (This is happening to my '88 SE right now.) I suppose the added cornering load stops the noise. Don't know if this applies to rear bearings, though.

 

I also get a howling noise when im going up a hill, usually in a high gear. When I start to speed up and rpms go up the sound goes away.... Have any ideas?

 

That is the sound of your engine howling about being in a high gear at low rpms

 

No actually the howling is comming from the back im pretty sure. I think it might be the bearings because when I went to autox they told me my bearings are loose, but they would still let me do autox. They told me if I keep on doing autox that I should fix my bearings.