2001 5.3 4wd silverado differential - I am getting ready to replace the fluid in my differentials and lookep up the lube type in the manual. Front: SAE 80W-90 Rear: ...

I am getting ready to replace the fluid in my differentials and lookep up the lube type in the manual.

Front: SAE 80W-90
Rear: SAE 75W-90 SYNTHETIC LUBRICANT

I plan on using Mobile 1 75-90 synthetic in the rear, but I am not completey convinced that I can use synthetic in the front. I have read that the 75W-90 SYNTHETIC can be used in both.

Is that correct?

2001 5.3 4wd silverado

You're fine to use synthetic 75w-90 in both the front and rear. http://www.amsoil.com/mygarage/ProductRecommendations.aspx?FromIndex=1&url2=2001+CHEVROLET%20TRUCKS+SILVERADO%201500%20PICKUP+T

how much does each differential take?

5 qts is enough to do both. Use 75W-90 synthetic for both even though the front says differently. Only reason they never put synthetic in the front is to save a $.

Is the rear gasket reusable?

No it is not reusable.

SLCCHEVY wrote:Is the rear gasket reusable?

It's about $10 to replace. Do it- you'll be glad you did!

Here's a usefull link:

Here is another helpful link, if I do say so myself!
How to Change Rear Differential Fluid

HI,
75w-90 is fine front and back. Been running this exact same set-up in our '09 for close to a year now. In Minnesota, synthetic is the only way to go.
EKinMN presents a very useful post - review it before you start.
Although I enjoy the advantages of 4x4 in the winter, I want the best possible mileage I can squeeze out of my truck. ALL my fluids and greases are synthetic. They last longer, protect better, and offer mileage enhancements conventional lubricants just can't match.
Glen