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Differential Fluid ??

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Old Jul 30, 2007 | 03:13 PM
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Default Differential Fluid ??

I'm getting ready to change the fluid in my differential and transmission. The Owner's Manual says to use GL-5 Lubricant. The last time I replaced the Diff. Fluid, I bought it at the Chevy dealer along with the Additive.

Is that what I should use, or, are you guys using Mobil 1 Synthetic or another brand?

Thanks,

Dave
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Old Jul 30, 2007 | 03:20 PM
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I'm sticking with the GM recommended lube and additive.
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Old Jul 30, 2007 | 04:39 PM
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Lucas 85-140 gear oil and GM additive in the diff.
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Old Jul 30, 2007 | 04:41 PM
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I was planning the same thing, and using the GM fluid like I got from the dealership last time.

Certainly if there is an equivalent, or better commercial product out there at about the same cost as the GM product, I would try it.
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Old Jul 30, 2007 | 04:45 PM
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I used NAPA 75W90 gear lube that has the additive. My opinion, for what it's worth, I wouldn't use synthetics in these old Vettes that were not designed for it. They will often leak .
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Old Jul 30, 2007 | 04:57 PM
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Originally Posted by GTR1999
Lucas 85-140 gear oil and GM additive in the diff.
quick question, what is the GM additive? i just filled up my diff. last night with Lucas 85-140 and no additive.
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Old Jul 30, 2007 | 06:01 PM
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Originally Posted by another-user
quick question, what is the GM additive? i just filled up my diff. last night with Lucas 85-140 and no additive.
It's GM's secret "snake oil" !
It's not cheap! , but it's worth it. See GTR1999's comments above.
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Old Jul 30, 2007 | 06:02 PM
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GM limit slip additive for the clutches to slip in corners. Any GM dealership will have it in 4 oz bottles for about $10.
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Old Jul 30, 2007 | 06:51 PM
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Originally Posted by chevy69
I'm sticking with the GM recommended lube and additive.
Thanks chevy69, ...I decided to keep it all GM!

I went to the Chevrolet dealer where my car was purchased new and bought 3 bottles of fluid and 1 bottle of additive. I even got a little discount.
The fluid cost me $6.68 per 23 oz. bottle and $9.42 for the 4 oz bottle of additive. I'll be getting a little dirty tomorrow morning.
The Chevy dealer is on its third owner, but my Vette is only on its second owner.

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Old Jul 30, 2007 | 09:16 PM
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I realize this is but can you run me through the fluid change procedure -- I've never done it and want to turn the wrenches myself this weekend. She needs it.
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Old Jul 30, 2007 | 10:39 PM
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Originally Posted by Shoevette
I realize this is but can you run me through the fluid change procedure -- I've never done it and want to turn the wrenches myself this weekend. She needs it.
Well, the nice design team at Chevrolet didn't put a drain plug in our differentials, so you have to suck the fluid out through the fill hole. I use a hand pump with a rubber hose attached to the end and suck out as much as I can.
Then, I add the 4 oz. bottle of additive and use that container to add new fluid 4 oz. at a time. I'm retired so I have plenty of time to do this.
I guess I could also run some clean fluid through the hand pump, then use it to add the new fluid.
Luckily, the transmission does have a drain plug so it goes pretty easy.

I'm sure someone else will post their procedure...It's always good to learn new techniques.

*NOTE* I just finished changing my differential fluid and I used my new suction pump to remove the old fluid. I put the additive in first, then, after cleaning my suction pump, I used it to add 2 bottles of fluid and topped it off using the additive bottle to squirt fluid into the differential.

Last edited by 71 Green 454; Jul 31, 2007 at 01:12 PM.
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