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What is the recommended gear lube for the '06? I had the lube changed to synthetic (not knowing it already had it in it shame on me) and it hates life with a passion. The fluid that was put in was Red Line Lightweight Shockproof 75W140. The service manual says the rear end should have 75W140 and gives a part number of 89021809. Went to the dealer and they said the number was valid, but not available in the US. They said they had never had to service the rear end of a GTO so they didn't have a clue. The only synthetic they had was 75W90 (corvettes and CTS-V's use that).

Help!! It has gotten bad enough that I have parked the car in fear of damaging the rear end. It binds up real bad when backing up and in turns. We added more additive and it helped for a little while and then started acting up again.

Recommendations please...:confused
 

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I use Mobil1 synthetic 75w-140 plus the GM friction additive, 1oz. You can buy the Mobil 1 from Autozone and other autoparts stores. The friction additive will need to come from the dealer or GM parts direct.com. I do not have the GM part number handy at the moment :cheers
 

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The GTO does take a 75w140 gear lube with a friction modifier additive. Redline makes two versions of synthetic 75w140, one with and one without the friction modifier additive. I'm wondering if you got the one without. Adding a 4 oz bottle of friction modifier may help. AMSOIL makes a bottle for adding to gear lubes without the additives:
AMSOIL Slip-Lock Differential Additive

FYI, the AMSOIL Severe Gear Extreme Pressure Synthetic 75w140 comes with the friction modifer pre-added. :cheers
 

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I read up more on the Redline Shockproof line and I'm still not sure whether this fluid has friction modifier in it or not. The literature on it says it is a racing gear lube that can be used in limited slip differentials, which implies it has friction modifier in it, but they don't specifically say that. Sorry I couldn't help more.

My recommendation, drain the fluid and put in something such as the AMSOIL Severe Gear 75w140 or Redline 75w140 (not the 75w140NS) that is a known quantity. :cheers
 
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