: noise still coming from the back...need help.



4DoorZ06
04-04-13, 11:01 AM
I changed my differential oil like I was told I should but the same rubbing type of noise in the back of the car is still there. Is there anyone who knows what this could be?

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Also my front left shock is going out. I need to know wich front shocks would be good to put on without breaking the bank too much.

darkman
04-04-13, 01:44 PM
I would put OEM FE4 shocks on the front.

As to the rubbing sound we need more information as to what it sounds like and under what conditions it occurs.

rand49er
04-04-13, 03:11 PM
As darkman mentioned, is that "rubbing" coming only when you're turning? ... or going straight? ... or any motion at all?

I'm assuming you've looked under there to make sure there isn't some branch dragging under there or a piece of cardboard caught in the wheel well.

Bacon V
04-04-13, 03:46 PM
Rubbing as in metallic? Could be anything from a rotor dust shield dragging on the rotor to the differential whining. The diff in these cars is known to whine at times - you can reduce it with certain lubes but others will not change it. Could be the diff as you suspect and you might need a different weight and/or additive to reduce it. Could also be brakes dragging or rubbing on a corroded rotor edge. Can you jack up the rear and rotate the wheels by hand to see if you can reproduce it?

JDB
04-04-13, 04:12 PM
Can you describe the ruckus?

4DoorZ06
04-06-13, 04:01 AM
The noise is only when I am turning and in gear. It does not make the noise while turning in neutral nor when im going straight just when turning and in gear. It just sounds like metal and plastic rubbing if it makes sense.

rand49er
04-06-13, 09:37 AM
Your description sounds like the slip-lock additive wasn't added when the differential fluid was changed.

darkman
04-06-13, 09:46 AM
Your description sounds like the slip-lock additive wasn't added when the differential fluid was changed.

Agree.

4DoorZ06
04-07-13, 04:30 AM
So I took it to my mechanic and he said the clunking is caused by the motor mounts. Are the UMI motor mounts any good? The complete kit goes for $249

rand49er
04-07-13, 08:44 AM
... rubbing type of noise in the back of the car is still there ...


... the clunking is caused by the motor mounts ...That could well be, but did you get the first problem solved?

Bacon V
04-07-13, 11:36 AM
Can you describe the ruckus?

lol, havent seen a breakfast club quote in a while

J W
04-07-13, 03:00 PM
Mine has been sitting all winter. I brought it out yesterday and while driving i would hear a clunking sound when shifting It did not do it all the time but i did notice the sound. Could that be the motor mounts. It has 41k on it.

darkman
04-07-13, 03:20 PM
Mine has been sitting all winter. I brought it out yesterday and while driving i would hear a clunking sound when shifting It did not do it all the time but i did notice the sound. Could that be the motor mounts. It has 41k on it.

It could be the motor mounts, but there are other possibilities. The differential bushing would be my first guess. The motor mounts are liquid-filed units and leak brown/rust color fluid when they have failed. You could look for leakage with the car on a rack or jack stands.

J W
04-07-13, 04:05 PM
Ok thanks, I'll lift it tonight and see if there's any leakage. If it's the differential bushings would there be a way to tell.

Bacon V
04-07-13, 04:13 PM
Yes, you can usually push up hard on the bottom of the diff and get it to move a good amount if it's failed. You can also sometimes see rubber chunks missing and/or hanging out

4DoorZ06
04-07-13, 08:18 PM
The first problem is still there. I took it to jiffy lube and asked specifically for the GM oil and additive. They ended up putting Pennzoil and I'm not even sure if they put additive. Does the Pennzoil work because the noise never went away.

darkman
04-07-13, 08:45 PM
The first problem is still there. I took it to jiffy lube and asked specifically for the GM oil and additive. They ended up putting Pennzoil and I'm not even sure if they put additive. Does the Pennzoil work because the noise never went away.

Pennzoil lists synthetic and non-synthetic GL-5 specification gears oils. All of those I found indicate that they are suitable for limited-slip differentials which means they come with some additive in them. However, there is no way to know that the friction coefficient is correct for any particular differential. Since yours may still be making noise, I would add more additive. Most autoparts stores carry one brand or another of gear oil friction modifier. Just drain out some the existing fluid and add the additive. (or ask Jiffy to do so.)


(The original Techinical Service Bulletin on this issue (2004) actually suggested removing the limited-slip clutch packs from the differential and soaking them in the additive to cure the condition. While that is no longer recommended, it does suggest that some extra additive may required to cure the issue once it developements.)

4DoorZ06
04-11-13, 12:53 AM
So Just today I noticed that now its doing the noise even in neutral and going straight but its not very loud. Any ideas. now of what it could be?

Stalicone
04-11-13, 02:20 PM
I had a terrible rubbing noise coming from the rear diff. It was when the car was in gear and turning at slow speed, like when parking. It was like a grinding/rubbing noise that sounded like bad bushings or bearings. It was driving me nuts since I had recently had the diff serviced and used Royal Purple. Another mechanic I know, who has a GTO recommended Amsoil with the slip lock additive. He also told me it would take like 2 days for the noise to abate after changing the fluid. I told him straight that his suggestion sounded like so much bullshit...I mean no "fluid" could possibly make a noise like THAT go away...and whats with the 2 days??? 2 days for "oil" to make a HUGE rubbing noise go away?

Well, wouldn't ya know it. The guy was like a fortune teller. We put the Amsoil in and right away I noticed the sound started changing...it wasn't so...hair raising. Sure enough, 2 days later, the sound was completely gone. Unreal.... From oil.

4DoorZ06
04-11-13, 08:27 PM
sounds like you had the same exact problem that I do. I'm am going to try this and if it works than that will surely make me happy. Do you know how much oil and additive he put in your car?

Stalicone
04-17-13, 12:37 PM
To answer your question, I actually called the mechanic who cured mine, and this is what he said: "You really need the AC Delco 35/90 full synthetic with their "friction modifier". About 2 qts. of the 35/90 and 2 ounces of the friction modifier. Because the the AC Delco is hard to find or available only through the dealer, we used Amsoil 35/90 synthetic on yours with 2 ounces of the "slip lock additive."

I can tell you that it cured mine, and it was was making so much noise it was setting my teeth on edge. Again, it was so hard to believe that mere oil could have such a profound effect, but it did....I'm certainly not claiming this is your issue. I'm just relating my story, and a fluid change is a lot cheaper than wrenching on a rear end!