Front Differential fluid change

Cowpie · January 5, 2017

They've changed in the newer manuals:

2016 manual:

Front Axle – Four-Wheel Drive SAE 75W-90 Synthetic Axle Lubricant

Rear Axle (1500 Series) SAE 75W-85 Synthetic Axle Lubricant

(IIRC, the 2014 was 80W-90 for front, the same as '16 for the rear)

The 75w85 is purely CAFE standard generated recommendation. A 75w90 will still work just fine in place of 75w85. I have just avoided all the confusion for years now and just use 75w90 in all my diffs.... car, pickup... even my semi truck. One is going to have a tough time building a case that 75w90 will not work in a very wide range of applications. If it can endure 300,000 miles between lube changes in a commercial truck that is grossing up to 80,000 lb and doing it in over 100F temps in the summer and sub zero in the winter, gonna be a tough sell to convince me it won't work just fine in both diffs of a pickup.

While 75w85 is now also becoming a factory lube for even heavy commercial trucks, at least the OEM's are quite clear in stating it is all about chasing down that last little bit of fuel economy. I won't bite at that. Diffs are far too expensive to play fast and loose with because some government hack thinks that a 75w85 will do as well as a 75w90. I am not going to play in that sandbox. So if I had a vehicle with 75w85 as factory fill, I would dump it for 75w90. Protection of internals is far more important than the less than 1 tenth mpg fuel economy I might gain.

80w90 tends to be and conventional based lube only. 75w90 is generally a synthetic. And synthetic base oils do have an advantage in high heat, and especially shearing forces that go on in a diff.

FL335i · January 5, 2017

^AMEN Cowpie! My thoughts and experience exactly. GM was doing 80/90 dino in the front diffs b/c their setup does not spin (completely) in 2wd so from a CAFE perspective GM spending the additional money on 75/90 front diff fill was not going to gain them anything. Plus a lot of people don't even use 4wd... so it lasts a long time. In the rear they spent the money on 75/85 Syn for CAFE gains. Toyota does this too. My '09 TRD taco had 75/85 in the rear diff. I go 75/90 Syn all around also....

SteveCZ · September 4, 2017

So I just did my front and rear diffs, and my transfer case today for the first time. Thanks to these forums and some "youtubing", it was straightforward and simple.

I used AC Delco 75W90 Synthetic "Grape Juice", yes I know, I overpaid or whatever, its my prerogative

Hardest part was cracking the rear pumpkin to let the fluid drain, loosened all the bolts on the rear diff and gave it a little yank and drain-o-matic.

All three fluids were nasty, with a decent amount of metal on the magnets on all three. Glad I did them, and now they are good until I sell the truck.

Next project is swap out the transmission fluid by disconnecting the cooler line going to the top of the AC condenser. That and break my arm in three places so I can drop the pan and swap the filter. Might be a good reason to sawzall the exhaust off and put aftermarket....