What kind of diff fluid do I need for a GMC Truck?
From 2002 on same with front axle, synthetic 75W-90 is required. From 1999 to 2001 can use but did not come with it. So, 5 qts should be enough to do both front and rear providing you do not waster any. Warning-As previously mentioned DO NOT add an Limited Slip Differential additive to a G80 Locking Rear Differential.
What kind of lube does a GMC truck use?
Since the 1999 Model year the factory fill for the rear axle of all trucks has been 75W-90 Synthetic Gear Lube. From 2002 on same with front axle, synthetic 75W-90 is required. From 1999 to 2001 can use but did not come with it. So, 5 qts should be enough to do both front and rear providing you do not waster any.
When does the rear differential lock on a GMC Truck?
Trucks use a Locking rear differential which completely locks up when one wheel spins more than 100rpm more than the other and will remain locked until about 25 mph. After 25 mph is will not lock.
How many bottles of rear diff fluid do I Need?
80w-90 and buy 3 bottles. Should be about 2 1/2 qts. You should need either a 75w90 gear oil w/ limited slip additive already in it or you can buy the additive seperately. I got Mobil1 75w90 LS from Advance cuz it’s got the additive already in it (about $11/qt). No additive needed if its a G80. 80w90 is fine, tough to find the 75w.
From 2002 on same with front axle, synthetic 75W-90 is required. From 1999 to 2001 can use but did not come with it. So, 5 qts should be enough to do both front and rear providing you do not waster any. Warning-As previously mentioned DO NOT add an Limited Slip Differential additive to a G80 Locking Rear Differential.
Since the 1999 Model year the factory fill for the rear axle of all trucks has been 75W-90 Synthetic Gear Lube. From 2002 on same with front axle, synthetic 75W-90 is required. From 1999 to 2001 can use but did not come with it. So, 5 qts should be enough to do both front and rear providing you do not waster any.
What kind of oil do I need for front differential?
You need a 75w-90 gear oil for both front and rear differentials. Do you know if you have the auto push button transfer case or a manual transfer case. If you have the auto you need to go to the dealer and get the Auto TracII fluid. If you have the manual then it takes Dexron ATF.
Trucks use a Locking rear differential which completely locks up when one wheel spins more than 100rpm more than the other and will remain locked until about 25 mph. After 25 mph is will not lock.