Clunky Rear end
Thread Starter
Safety Car
Joined: Feb 2006
Posts: 4,855
Likes: 2
From: Columbia South Carolina
Clunky Rear end
Guys, when I take a corner my rear diff Clunks. Is it because it is so warn or the wrong lube? I have checked it several times and i know that there is W90 in it up to the plug. any ideas?
Melting Slicks
Joined: Oct 2004
Posts: 2,662
Likes: 8
From: Knoxville Tennessee
90 weight gear lube is the wrong lubricant for your diff. It is a positraction unit and requires special fluid with posi additive. You can buy it at the chevy dealer and most auto places have it. You need to change your fluid if 90 wt is in it. The clunking sound is the posi clutches sticking as you go around corners. The correct lubricant will allow them to slip when going around curves. Hope this helps.
Bernie
Bernie
Tech Contributor
Joined: Aug 1999
Posts: 15,175
Likes: 3,989
From: Connecticut, USA
I'll respectly disagree,90 wt is the correct oil to use. It is used in addition to the GM additive. Many gear oils will say good for use with limited-slip but you still need to use the additive. There are some synthetic lubes that state they do not need the additive but on the advise of US Gear and Tom Watt, I don't use them.
You can try to change the oil and add 2 bottles of the GM additive but usually the clutches will "hammer" when they are the problem. This is from the preload of the 4 -400 ft/lbs springs keeping pressure on the sdie gears and clutches.Most noticable when the oil is hot and turning a corner from a stop.
It sounds like you have a backlash issue in the ring gear, was this rebuild recently? Does it whine while driving under load or decellerating?
You can try to change the oil and add 2 bottles of the GM additive but usually the clutches will "hammer" when they are the problem. This is from the preload of the 4 -400 ft/lbs springs keeping pressure on the sdie gears and clutches.Most noticable when the oil is hot and turning a corner from a stop.
It sounds like you have a backlash issue in the ring gear, was this rebuild recently? Does it whine while driving under load or decellerating?
Drifting
Joined: May 2004
Posts: 1,442
Likes: 2
From: Flanders NJ
Originally Posted by BerniesVette
90 weight gear lube is the wrong lubricant for your diff. It is a positraction unit and requires special fluid with posi additive. You can buy it at the chevy dealer and most auto places have it. You need to change your fluid if 90 wt is in it. The clunking sound is the posi clutches sticking as you go around corners. The correct lubricant will allow them to slip when going around curves. Hope this helps.
Bernie
Bernie
Gotta have that posi fluid in there in addition to the oil
Racer
Joined: Dec 2003
Posts: 304
Likes: 0
From: Pasadena Maryland
Sounds like the same exaxt problem I had with mine when I bought it in 1995. Thought the rear end was going to fall off. I bought a cheap jack rabbit pump and drained all the gear oil out. Filled with new oil and additive and ran it for a couple of days. Drained it a second time, filled with Amsoil Gear Lube and a bottle of Limited Slip Additive and haven't had a bit of problem with it since (knock on wood).
Premium Supporting Vendor
Joined: Aug 2001
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From: King George VA
Originally Posted by djgrelli
... Drained it a second time, filled with Amsoil Gear Lube and a bottle of Limited Slip Additive and haven't had a bit of problem with it since (knock on wood).
AMSOIL Severe Gear Extreme Pressure Synthetic 75w90
This diff fluid comes with the friction modifier already in it so a bottle of friction modifier should not be needed, but if diff chatter occurs, adding a bottle of this should help:
AMSOIL Slip-Lock Differential Additive
Hope it is a simple fix for you.
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Burning Brakes
Joined: Oct 2004
Posts: 763
Likes: 0
From: Loveland Colo
You might try jacking the car up by the shock mounts, grab your wheels at 12 and 6 o'clock and rock back and forth to check the play in your stub axles...I haven't verified it by a rebuild yet, but mine have so much slop I'm quite sure that's the source of my corner clunking (and tracking twitches).
Does that sound reasonable to you rear end/suspension guys out there?
John
Does that sound reasonable to you rear end/suspension guys out there?
John
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Thread Starter
Safety Car
Joined: Feb 2006
Posts: 4,855
Likes: 2
From: Columbia South Carolina
Guys, sorry I havent been in the forum for a while to reply, Thanks for all the info. I did recently replace the diff Bushings with Poly and the U-joints seem to be good. One question to everyone who posted a lube, Where can I get it? I have an Auto Zone and an Advance Auto (that I try to avoid) and possibly a NAPA within reasonable distance. And of course the internet. Thanks again to all replies.
Melting Slicks
Joined: Oct 2004
Posts: 2,662
Likes: 8
From: Knoxville Tennessee
If you are uncertain, just go to your local Chevy dealer and ask for the posi additive. Should take 2 small bottles. Once you get the additive into your diff. find a lot that you can do slow figure 8's in. As you make the different turns your clutches in the posi grab and let go, the additive helps this process and does need changing from time to time. If this is the problem, the clunking will stop.
Bernie
Bernie
Melting Slicks
Joined: May 1999
Posts: 2,897
Likes: 0
From: Moon Township PA
Originally Posted by 454_71Stingray
Guys, sorry I havent been in the forum for a while to reply, Thanks for all the info. I did recently replace the diff Bushings with Poly and the U-joints seem to be good. One question to everyone who posted a lube, Where can I get it? I have an Auto Zone and an Advance Auto (that I try to avoid) and possibly a NAPA within reasonable distance. And of course the internet. Thanks again to all replies.
Gary