I am going to be replacing the fluid in my truck's front and rear diffs.

What would the capacity for each?

What is the recommended weight?

Also, I will be using Amsoil. My truck has 4.10 gears with the factory rear LSD, do I need to add any friction modifier when using Amsoil?

 

No friction modifiers for our lsd, but the amsoil already has it in it. I use 75/90 severe gear, just did my second change on the axles at 40k on the oil. Rear takes 3.81 and front takes 2.37 quarts, but buy 7 quarts. Also buy the amsoil gear lube hand pump, makes it so much easier.

 

I seem to usually buy 7 qts, tried M1 75W140 one change but have gone back to M1 75W90. I let the bottles sit in hot water for awhile, carefully wipe them dry before using them, and just use the caps with the tips that come on the bottles. Don't overfill.

 

Depends on your application.

Nothing but towing - 75/140

Some towing, but mostly driving around 75/110

Never towing, never going to tow 75/90

Dont get that hand pump, its a waist of money, just pop off your bottom bolts then start loosening up the other bolts from the bottom up. it will all drain out. then spray engine cleaner all in your pumpkin and your cover. Let it sit for a few and wipe it dry. you will be wiping away a metallic paste that looks like anti-seize. let it sit out in open air for a hr or so wipe it all again then Put the cover back on, fill the oil until it starts draining out of the fill hole. drive it around for a few minuts, check the oil level again and your done.