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Rear differential fluids

The Invisible One

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I was at a dealer today and asked what fluids are used in the rear differential since the owners manual says nothing. Here is what I found:
75w-90 Dexron LS p/n 88862624
According to the Corvette forums, this is a group ii/iii oil made by Petro Canada marketed as full synthetic with limited slip additive.
The Twinster clutches use Pentosin CHF 11S p/n 88901975
I didn't find quantities used for either fluid.
 

The Invisible One

New member
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3
For those that like to line up tools before doing a job, the rear differential uses 10mm allen wrench for drain and refill ports. The refill port is very close to the rear sway bar, so using an allen socket didn't work for me, had to use old school wrench. Luckily the bolts were not super tight. While there I checked the fluid (75W-90 with limited slip additive) level and color, both were great after 3700 miles.

I did not check the clutch pack drain and fill ports for size, but can say they looked about 5mm or 6mm allen. The fill port is way up high and will be a bit of a pain to reach when time comes to do that fluid (Pentosin CHF 11S).
 

mooooo

Active member
111
76
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tourx
For those that like to line up tools before doing a job, the rear differential uses 10mm allen wrench for drain and refill ports. The refill port is very close to the rear sway bar, so using an allen socket didn't work for me, had to use old school wrench. Luckily the bolts were not super tight. While there I checked the fluid (75W-90 with limited slip additive) level and color, both were great after 3700 miles.

I did not check the clutch pack drain and fill ports for size, but can say they looked about 5mm or 6mm allen. The fill port is way up high and will be a bit of a pain to reach when time comes to do that fluid (Pentosin CHF 11S).
You need an extension or a longer hex bit on your socket, like this one.

you are probably expected to use a pump to fill the clutch packs.
 
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