Changing differential fluid - A step by step "HOW TO"

I’m a fan of removing the spare tire to do the rear diff so you can pour the gear oil in from the bottle. Good time to spray the tire hoist mechanism and cable with fluid film also.

 

Exactly what I did on my last fluid change. I also had the back end on jack stands with the rear suspension at full droop. In this configuration I was able to comfortably sit underneath and pour the fluid into the fill hole using the nozzle on the bottle.

 

Truck on level ground? Or was nose down a little?

 

I just did my rear diff and transfer case this afternoon on level ground and my rear diff took 3.5 quarts. The old oil had 49,500 miles on it and it looked very good. The transfer case oil looked brand new. I need to pick up some more oil, because I only have a quart and a half (3 pints) and the front diff calls for 3.2 pints. Oh well. A project for another day.

 

You're supposed to ask, "What's a henway?" Then he can give you the dad joke response.

So what's the opinion on 75-90 synthetic vs 80-90 regular? The 75-90 will cost me about $60 for 6 quarts and I can get the 80-90 for about $20. Seems to me they both end up 90 weight when warmed up. Am I missing something?

 

you be missing about $40 bucks if you run 75-90.

i used Valvoline™ High Performance 80W-90 Gear Oil without issue.

 

I used 80-90 in my rear diff and no issues so far. I live in GA so it doesn’t really get cold enough down here to worry about the small difference IMO.

 

After doing the rear diff and t case last week, I finally got around to doing the front today. The oil looked similar to the rear, so I would suggest if you do one, you might as well do the other.

 

I replaced the factory 75w85 with synthetic 75w90 and noticed my gas mileage dropped about 1 mpg. I've only checked 2 tank fulls so far and it has been in the mid to high 90's where I live so the ac has been on quite a bit, but it feels like I have to push the gas pedal a little harder to get going even with the ac off. It could be my imagination, but I wanted to see if anybody else has noticed this.

 

I imagined the same thing. thought it was like i filled with molasses or something. In reality I am still getting under 20 and it's been 114 this week.

 

I'm glad I'm not the only one that noticed this. It might just be the difference from going from old oil to fresh new oil. I know 75w90 is safe to use, so it's probably no big deal. Normally I get 18-19 mpgs this time of year, but since the diff service I'm getting 17-18.

 

1 mpg.. That could be from anything. Safe to use.. ECGS/ARB recommends 85-140 when you get gears/lockers done, so as long as there is diff oil in it you are safe.

 

Yeah lots of guys use 140 weight so are they getting like 10 mpg?

 

By the ideas brought forth here, yep.

 

After I changed the gear oil in the rear diff, I immediately noticed it took a little more pedal to get going. I doubt it's from the 75w90 weight oil, but maybe I put too much oil in the diff. I filled it until some dripped out of the fill plug on level ground, however, it took 3.5 quarts, which is a little more than the 3.15 quarts (6.3 pints) it's supposed to take. Again, it's probably no big deal. I was just curious if anyone else had experienced this.

 

Do I add one tube of LSD additive to both the front and rear? Or do I only put it in one of the differential thanks!

 

Not required, at all.

 

Don’t need it in a 2015

 

pretty interesting, ive been using the REDLINE 75w85 in my rear diff since I bought the truck and I use 75w90 in the front diff/transfer case, to offset the high cost of REDLINE I was hoping on using SUPERTECH 75w90 in everything next the cost of REDLINE is too much but I can understand u losing some power/mpgs because that stuff is thin as water compared to 75w90

 

Thank you.

Thank you.
What was the cut off to needing the additive? I just went off the original listing in the form. Saw that I also had the sport.