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When doing the front axle fuild change do I still need to change the vent cap if going to syenthic?

Thanks
 

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Only if it is not a white cap. You should be good if it is a 06. My 05 had a white cap.
 

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Not the front.
Factory fill for the rear diff is synthetic 75w90 "Grapejuice", but the front is 80w90 conventional.
 

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My 06 came with the Grape Juice 75w90 in both diffs front and rear.
 

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My front was a cloudy yellow when I drained it. It also had a small turd connected to the magnet.
 

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sorry for the stupid question but what is the grape juice? I think when I serviced mine last week I used a synthetic posi approved fluid I got at advanced auto parts. Don't remember the brand name but it was a good name brand seems like it was around $15.00 per quart. Is this grapejuice stuff better? I still have the front to change just waiting to get a few miles on the front before changing as I have not used it yet.
 

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Beginning in 2006, the Front Differentials are factory filled with Synthetic, so you should already have the white cap.

Jperry, Grape Juice is the nickname for the GM Synthetic Axle Oil. The part number is 12378261 and retails for $27.55 per quart from GM. You can use this oil if you like, or any good synthetic 75W-90 or 75W-140 if towing heavy.
 

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If the vent is not white, what color is it. My '05 LLY, the vent was a tan color? I bought a new one anyway????? I used Mobil 1 75w90 front and rear $8.88/qt Advance Auto.
 

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Interesting... I've heard that they went to white as early as late '04, but it could have been later, or maybe you have an early '05 that slipped through.


I guess having an LLY is not insurance that you have the white cap.
 
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