Differential Oil

[bama21fs]

I have a 1999 Chevy Silverado 1500 Z71. I am planning on changing the Differential Oil, front and rear. I am getting CONSIDERABLY conflicting information on what to use to replace the oil. I want to use Lucas 75w-90 Gear Oil. Because of the vastly differing facts... I have no idea what to do in order to change the oil.

 

 

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[Black02Silverado]

Welcome to GMT!

 

What conflicting info? 

 

The front diff you fill until it starts to come out the fill hole, which is just about 2qts. 

Rear diff you fill to about an 1/8" below the fill hole and is about 2.5qts.

A 75w-90 synthetic is recommended.   

 

AMSOIL's new squeeze pack makes diff oil changes a breeze.

 

CAPACITIES:

Engine, with filter..........6 quarts [1] Cooling System, W/AC Initial Fill..........15 quarts Passenger Car & Light Truck Antifreeze & Coolant AMSOIL Antifreeze and Engine Coolant Cooling System, Without AC Initial Fill..........13.9 quarts Passenger Car & Light Truck Antifreeze & Coolant AMSOIL Antifreeze and Engine Coolant Automatic Transmission, 4L60-E Initial Fill..........5 quarts Automatic Transmission, Total Fill    4 speed 4L60-E..........11.2 quarts Manual Transmission, NV3500/MG5..........4.2 pints [2] Differential, 11 RingGear Dana GMT 800 Rear..........8.5 pints Differential, 8.5 RingGear AA GMT 800 Rear..........4.2 pints Differential, 8.6 RingGear AA GMT 800 Rear..........4.2 pints Differential, 9.5 RingGear AA GMT 800 Rear..........5.5 pints Differential, 10.5 RingGear AA GMT 400 Rear..........6.3 pints Differential, 11 RingGear Dana GMT 400 Rear..........8.5 pints Differential, 8.5 RingGear AA GMT 400 Rear..........4.2 pints Differential, 8.6 RingGear AA GMT 400 Rear..........4.2 pints Differential, 9.5 RingGear AA GMT 400 Rear..........5.5 pints Differential, 10.5 RingGear AA GMT 800 Rear..........6.3 pints Differential, Front..........3.6 pints Transfer Case, NVG 246..........4 pints Transfer Case, NVG 261..........4.6 pints

 

 

Edited January 26, 2019 by Black02Silverado

[newdude]

75w90 synthetic for both the front and rear, no friction modifier for either. 

 

When that truck was new, and up to the early 2000's, GM used to spec 80w90 conventional for the front, but had cold weather issues and issued a bulletin to switch it to 75w90 synthetic. 

[NothingbutGM]

Just check your owners manual. Can’t go wrong with that. 

[pat_this]

 

[08 GMC]

I, solely due to availability in my area, used the Mobil 75/90 wt synthetic oil in my rear end.

 

Any oil will work but you might have to go to further lengths to get a certain brand if you cannot find it locally.

[pinkieminidisc]

The front diff you fill until it starts to come out the fill hole, which is just about 2qts. 

Rear diff you fill to about an 1/8" below the fill hole and is about 2.5qts.

A 75w-90 synthetic is recommended.   

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