# Differential Growl / Clunk when turning



## stephen77375 (Feb 13, 2011)

Okay fokes I posted a thread last week seeking assistance to locate a new ring and pinion set for my car as the pinion decided it was done. I bought a new ring / pinion / master rebuild kit from 1320 engineering Chris is his name, nice guy btw! 

I had the local Chevrolet dealership do the install for me and for the first day after I got it back car ran great, no excessive noise no growling or clunking from the rear end. I just got back from making a 10 minute run to the bank ATM and on the way back when ever I turn and the LSD is unlocking I hear a growling and feel and hear a clunking noise coming from the rear end. Chevrolet mentioned no noticeable wear in the differential and said everything looked good. 

I had them use Royal Purple 75-140 w/ Friction modifier already present in the oil to lube the gears upon being finished. 

Any idea what might be causing this? Again new ring, new pinion, new master rebuild kit w/ all bearings, sleeves, gaskets, o rings etc.

Help please!


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## GTO JUDGE (May 14, 2005)

stephen77375 said:


> Okay fokes I posted a thread last week seeking assistance to locate a new ring and pinion set for my car as the pinion decided it was done. I bought a new ring / pinion / master rebuild kit from 1320 engineering Chris is his name, nice guy btw!
> 
> I had the local Chevrolet dealership do the install for me and for the first day after I got it back car ran great, no excessive noise no growling or clunking from the rear end. I just got back from making a 10 minute run to the bank ATM and on the way back when ever I turn and the LSD is unlocking I hear a growling and feel and hear a clunking noise coming from the rear end. Chevrolet mentioned no noticeable wear in the differential and said everything looked good.
> 
> ...


WRONG OIL..... Does not contain the correct FM.
Reference this thread: 
http://www.gtoforum.com/f39/gm-friction-modifier-45401/

DO NOT drive it. Get it towed right back to the shop, or do it yourself but get that oil drained and use the suggested oil in that linked thread.


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## stephen77375 (Feb 13, 2011)

GTO JUDGE said:


> WRONG OIL..... Does not contain the correct FM.
> Reference this thread:
> http://www.gtoforum.com/f39/gm-friction-modifier-45401/
> 
> DO NOT drive it. Get it towed right back to the shop, or do it yourself but get that oil drained and use the suggested oil in that linked thread.




Judge, I have that exact stuff in the garage, is it okay to add it to the Royal Purple or is an entire oil swap recommended? 

PS What I have is the Trans-X posi additive that is the correct stuff in which you speak of right?


PS...S After reading the other posts looks like the Trans-X stuff is NOT the correct stuff for me. Trying to find a Torco dealer in or around Houston that has some 85w-140 RGO and some Type F modifier... Such a PITA!!!!


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## GTO JUDGE (May 14, 2005)

stephen77375 said:


> Judge, I have that exact stuff in the garage, is it okay to add it to the Royal Purple or is an entire oil swap recommended?
> 
> PS What I have is the Trans-X posi additive that is the correct stuff in which you speak of right?


I have only used the GM FM. However others, as indicated use Torco with the Ford type FM. This rear end is sensitive to FM. Use the incorrect one you'll experience this symptom all over again.

Our Club's VP used Royal Purple and got the same affect you did, he went with the Torco with Ford FM and all is well. My suggestion is.... do the same. Don't fool around with other FMs, you'll keep blowing $$ and possibly risk damage.


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## stephen77375 (Feb 13, 2011)

Now to find a Torco dealer in Houston... This has been a stressful week, spend $21.99 apiece on two quarts of oil and turns out to be the most expensive (but wrong stuff). Then I look at the Torco dealer list from their website and there is no one close to me that has it. GM stuff isn't made anymore its just one thing after another w/ this car. I have no choice but to drive it until I get the oil and additive for it hopefully tomorrow or the next day if I can find someone local that has it, Guess I'll just go really easy on it and not try to overdue it or cause any extra harm.

Thanks Judge for your help brother always a pleasure.

If the LSD blows... True-Trac here I come.


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## GTO JUDGE (May 14, 2005)

stephen77375 said:


> Now to find a Torco dealer in Houston... This has been a stressful week, spend $21.99 apiece on two quarts of oil and turns out to be the most expensive (but wrong stuff). Then I look at the Torco dealer list from their website and there is no one close to me that has it. GM stuff isn't made anymore its just one thing after another w/ this car. I have no choice but to drive it until I get the oil and additive for it hopefully tomorrow or the next day if I can find someone local that has it, Guess I'll just go really easy on it and not try to overdue it or cause any extra harm.
> 
> Thanks Judge for your help brother always a pleasure.
> 
> If the LSD blows... True-Trac here I come.


Good luck.... but I urge you not to drive it. :cheers


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## svede1212 (Nov 1, 2005)

The cars in Australia put in Type-F FM and the proper way to add it to the Torco is starting with a fresh fill, add 1 1/2oz FM, drive and then test in a slow, hard turn. If still popping/noise then add a 1/2 oz more and repeat. Keep doing just until the noise goes away. There can be an ounce variance as we have a very inexact method of anti-slip with the metal cone "clutches". You want as little as you can to have the diff work the best. Too much can give you one wheel peel-outs. A GM mechanic knows next to nothing about these cars unless he owns one.


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## stephen77375 (Feb 13, 2011)

Update it's like a miracle. I can't get Torco down here in a timely manner so I used Valvoline 85w-140 with no friction modifier present with motorcraft type F modifier an low an behold noise is gone! One would never think two ounces of little blue stink bait smelling stuff could prevent all that clicking an popping but it did! Thanks Judge and Svede for all of your assistance. I've ordered Torco oil an their additive, valvoline an motorcraft is just a bandaid until the good stuff arrives.


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## GTO JUDGE (May 14, 2005)

stephen77375 said:


> Update it's like a miracle. I can't get Torco down here in a timely manner so I used Valvoline 85w-140 with no friction modifier present with motorcraft type F modifier an low an behold noise is gone! One would never think two ounces of little blue stink bait smelling stuff could prevent all that clicking an popping but it did! Thanks Judge and Svede for all of your assistance. I've ordered Torco oil an their additive, valvoline an motorcraft is just a bandaid until the good stuff arrives.


arty: ............. Amazing isn't it? Glad its resolved.


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## Sunkissedbrandy (Jan 23, 2020)

I just had the same problem with my 2006 GTO. Changing the oil worked like a dream! I am so thankful to have found these posts.


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