I have 40k on the ticker and never changed diff's. . .mostly because I don't know how, but am willing to learn. Just got the truck back from the dealer today from a lift pump failure and he tried to get me to give him $129.95 per axle for diff fluid changes. I guess after finding this post this evening, it most be an omen... I will definitely buying the fluids as soon as someone gets me headed the right direction and what fluids to buy...Dealer says I have to use theirs because they have additives in them
I just said OK and came home to get the real experts opinions(you guys)...
So what to you guys recommend???? Should I go ahead and purchase that new rear diff cover I've been eyeing or just change fluids and go on??? Any comments??? Thanks

 

OK so im not the only one- awesome. I've been searching other posts like everybody preaches here and it seems like word on the street is any good quality synthetic gear oil is fine as long as it is GL-5 rated. Everyone is either running 75W-90 or 75W-140. How do I know which weight is best for my application? I am also pondering a Mag-Hytec or similiar cover but may wait till the next fluid change. Also, is there any other special items of knowledge i need when it comes time to crawl under the truck and tackle this thing?

 

The magnet is on the fill plug, just take a 3/8 extension and take the plug off and clean the shavings. I was also scared about doing my front and rear changes but after hours of research i bit the bullet and did it. After I was finished i felt stupid for reading so much about it, IT WAS SO EASY TO DO!
I unbolted the bolts and let it drain. I then took the cover off to have a good look at the gears and spray around with brake cleaner to clean everything up. The gasket is re-useable so don't worry about having to buy another. Put all the bolts back in and I tighted down to 24 ft.lbs. I used 75w-90 mobil 1 synthetic GL-5 rated gear oil. If you tow a lot and heavy then that is when most people use the 75w-140. If not then the 75w-90 works very well. just make sure it is full synthetic GL-5. I filled the covers up basically untill it ran out the plug. The front 9.25 covers recommend 1/4" below the fill hole +/- 1/4" so thats basically saying you can run it out, same thing with the 11.5 AAM rears. Here is the amount of fluid you need, I did the math to break it into oz. for more precise filling:
· Rear differential – 122oz or 3.8qts

· Front differential – 76oz or 2.38qts

Total of 7 quarts

Fill it up and tighten the plug down to 24 ft.lbs and you are good to go. Hopefully this made since.

If you haven't already checked it out and need help with your fuel filter change, check my recent thread, I took pictures to help along too.

Good luck
Eric

 

I have over 56,00 miles on my truck and have only changed the motor oil... I guess it's time for me to change some of the other fluids too. But I don't tow much, and when I do, it's light.

 

i think they say every 15 k for warranty purposes, they have alot of stuff in those manual that sounds bogus, like youre not supposed to sit and idle for more than like 10 minutes or some bs, my old 99 i just sold had just as much idle time as it did drive time, theres no tellin how many times my dad pulled over and slept in that thing w/ it runnin on his weekly trip to oklahoma. they are just tryign to cover their a$$

 

I agree with Horsehauler's write up above. I also use Mobil 1 75w90 bought from my local Ghettozone.

I added a Mag-Hytec rear Diff cover. It is a nice piece and helps drain the fluid and let it run cooler. But I would not consider it a necessity. IF you want it and like the looks of it....get it. If not, you will be fine with the stock cover.

I recommend to anybody to get that first change done as quick as possible. After that....just use some common sense. I changed mine at 15k, 30k, and now im doing it again tomorrow at 50k.

 

Alright - thanks for all the info. Maybe ill pick up the fluid this week and change it next weekend. You guys have given me faith in myself

 

I parked mine downhill to do the change and held my finger over the lower half of the fillhole so I could overfill a little. It's still not up to where I'd like to see it. DC underfilled it and the wheel bearings were coated with dark gray, burnt on lube, when I bought the truck. Surprisingly, the wheel brgs still had preload but not the carrier brgs. I used 75w140 but next time I'll use 85w140 - an AZ. adjustment. Craig

 

I changed mine at 15K like instructed. I put 75-140 syn in at that time due to most miles are towing 16,000 pound fiver. I changed again at 45,000 when returning from Alaska - - looked like brand new. I will wait until 75K for the next one. Dealer agreed with my assessment.
Bob

 

i have 33k on my 03, havent changed it, probably will now, what is a good fluid i can go out and buy for it?

 

I run Mobil 1 fluid, it seems to be one of the popular brands.


What are you guys torqueing your bolts down to when re-installing your covers? Most people say 22-24 so I was just curious

 

sheeeeeew.........im happy my last truck didnt know I should change the fluid every 15k or she might not have lasted 380,000 without ever changing the diff fluid.......LOL

 

are you serious?

 

Nice post!!!!!

 

If you have the space to store it buy your diff oil in the 5 gallon can, that cuts the price a good bit. As for the dealer having oil with the special needed additives, check the manual. He was feeding you a line the AAMs do not need any additional additives, just make sure you use a good GL5 rated oil. I bought a 5 gallon can of Valvoline, changed at 15,000, 30,000 and now debating on changing at 45 or wait until 50,000.