Lately I notice that the rear end on my Camaro is making a strange noise when I make sharp turns in low speed (i.e. if you're going to pull into a parking spot) - The noise itself is almost sounds like when you have a rusty/dirty brakes and you let off the brake pedal just a bit, kinda like a low hum.

Oh, it's a 9-bolt with posi, 3.70 gears. I believe I did the pinion-and-ring setup right, and the backlash is .008".

I read some posts in this forum where people tried different kind of differential fluids. I know that GM does not recommend additive for the 9-bolt unit since it's the cone type. I currently use a regular Valvolione 80-90 oil. Should I try adding the posi additive or should I switch to synthetic? Please let me know if anyone encounters a similar problem and if you have a solution.

Thanks!!!

 

Since no reply yet , I'll try to rephrase the problem:

1. When the car is cold (just driving), everything is just fine. Things start to go south after about 10 minutes of driving.

2. After the car is 'warmed up', the rear end chatters around the corners when I drive slow and sometimes when I start slowly from a complete stop (straight).

3. The chatter is not continous. Kinda come and go at the same frequency with tire rotation. Eventually it'll go away above 10 mph.

I tried to do a little burn out today and it still lays 2 stripes of rubber.

Has anyone ever encountered this problem? Or if you have any idea what may be the issue with my 9-bolt rear end, please please let me know......
I really have no idea what's going on and would like to get some insights before taking everything apart.

Thanks guys!

 

It sounds like it's a worn pinion bearing.

 

The pinion bearings are new, along with the crush sleeve. They're torqued to spec. Correct me if I'm wrong, but the pinion bearings wouldn't know the difference whether the car is straight or turned, would it?
Thanks for the reply.... please please keep 'em coming

 

Needs posi additive in the fluid.

That's what that stuff does, is stop all that chattering and groaning and carrying on.

There's no particular reason that the orientation of the friction surface of the clutches, i.e. whether they are cone-shaped or plate-shaped, makes any difference to the need for the friction modifier.

 

The spider gears in your limited slip could be going out. I had the same problem in my car, the car would make noises when I made left or right hand turns. But it would work fine when I drove straight. It has to do with the limited slip disengaging. But start with the posi additive, it might solve your problem for only a couple of bucks.

 

After being around 2 9-bolts, I'd call it normal for the cone type posi. Both had the "chatter" when cornering, the clutches grabbing and releasing.
- I too was told not to put ls additive in the 9-bolt, reason being something to do with the clutch material not liking the additive. - I would think the additive would stop the noise, but if it's at the cost of wearing out the posi sooner, I think I'd live with the noise.....

 

Hi guys,

Thanks for all the replies!!!

As for using posi additive, I have tried the following:
1. Use regular 80W-90
2. Use synthetic 80W-90
3. Use synthetic 80W-90 with 1/2 bottle RedLine posi additive
4. Use synthetic 80W-90 with full bottle of RedLine posi additive
5. Use Lucas Heavy Duty 85W-140 ~ I tried this since I realized I may be getting too 'slippery' with the posi additive, so I went the other way.

So far the 85W-140 works the best. The chatter / shudder is less but still there. What puzzled me is why is this only happens the the car warms up and why does it do it when I drive straight in low speed too......
However, the posi still works , laid 2 stripes of rubber....

I may just have to live with the noise until the day I sell the car

Thanks again guys, and please let me know of any other opinions.....

 

Update:

The noise disppears when I ride on the brake!

Maybe this is not the posi issue after all..... I wonder if the wheel bearings somehow is not set right that the axle wobbles / moves in and out. So riding on the brake is somehow fixing the axle in place....

What do you guys think?

 

I had a buddy that had the exact same issue,come to find out,his axle on one side would move out during a sharp turn,move out like 1/4 in or so but when appling the brakes the axle if it did have in and out play was held in place,if this is your problem, you can either go inside the rear end and fix it,or get some new(thicker)brake pads,witch my buddy did...

 

I found out last night that my real problem was the right side gear (inside the posi) wobbles. With the rear of the car on jack stands, I removed the right axle and place the car in D. Looking down the axle housing, I can see where the female-spline casted into the side gears wobbles.

So you're right, by holding the brakes it kinda holds the axle in place.

Anyone has the problem before? If so, can you tell me what's causing it? I wonder of one of the spring broke.

Ideas, anyone, please.............

 

That rear should take gl-5 gear oil .No additive...
It is a cone type rear .No clutchs..