A.D.D is auto locking hubs. In other words, you don't have to get out and lock in your hubs when you put it in 4 wheel drive.

 

ADD stands for Automatic Disconnect Differential.

The ADD system does not have hubs, auto or manual.

The ADD system uses vacuum to lock or unlock one of the front axles from the differential to go from 2WD to 4WD.

 

A.D.D stands for Automatic Disconnecting Differential and only refers to the front diff on 4x4 models. Any good gear oil will work for you (75w-90, for example). I recommend Redline.

 

attention deficit disorder. . .

 

^A common misconception, I think. And no, you do not have A.D.D. as your truck is 2WD.

A name brand 75W-90 or 80W-90 will work just fine for your back differential. You will need a 24mm socket, which I had to go buy just to do this job. Seems unnecessarily large to me...

If you have a 15/16" socket that is pretty dang close, i think it's actually a little tight, but if you tap it on there a bit it may work. It's up to you if you want to push your luck.

Also, you are definitely going to want to invest in a $5 little plastic pump that goes into the bottle of oil. Trying to get it in the diff just by squeezing it out through the little nozzle on the bottle is near impossible, and even if it's possible it's a big time PITA. When you go to Checker auto or wherever to buy the oil, they should have them. No need to buy the industrial strength one, the cheapy should work just fine.

Take the fill bolt off before the drain bolt, just in case you cant get the fill bolt off, you don't want to be stuck with a diff with no oil and no way to get more back in. Just a suggestion, happened to me on my front diff, all my muscle and a breaker bar couldn't get the fill bolt off. Need an air wrench...

 

Before attempting to change differential fluid.... make sure that fill bolt comes off first. Mine's totally stripped... so i had to remove the breather and fill from there.

and my breather works

 

Something else you can try is a piece of clear hose. Cut the tip off of the bottle, run about 2 feet of clear tube, and squeeze. about a buck for the hose.

 

For the differential, use a GL-5. If you want to go with the best, that would probably be Amsoil Synthetic Severe Gear 75W90:
http://www.amsoil.com/storefront/svg.aspx

or Red Line's Synthetic GL-5:
http://www.redlineoil.com/products_gearlubricants.asp

Sometimes you can find Royal Purple's Synthetic Max Gear 75W90 or Valvoline's full synthetic Synpower in an Autozone, and they're not bad choices - either would be better than the non-synthetic oils.

BTW, if you have a manual trans, use a GL-4, NOT a GL-5. Red Line's MT-90 and Amsoil MTG are the two that are most often recommended. I use MT-90 and love it.

You might find this comparative study of gear oils by Amsoil interesting reading:
http://www.amsoil.com/lit/g2457.pdf Since it was commissioned by Amsoil I guess we shouldn't be too surprised their product came out smelling like a rose, but to be fair it is an excellent gear oil.

This site has some good info, too:
http://www.buyersguide.com/GearOil/Automotive/

 

For the differential, use a GL-5. If you want to go with the best, that would probably be Amsoil Synthetic Severe Gear 75W90:
http://www.amsoil.com/storefront/svg.aspx

i would say stick with amsoil for everything...cost me 180$ cause i get a discount off amsoil to do my whole truck; front, rear, t-case, oil, tranny, filter, hell even amsoil engine cleaner. plus a extra 2 gal jug of oil..u can never ever go wrong with amsoil. id love to see if another oil out perform amsoil cause nothin can. anywho thats my 2 cents..lol..

 

Yes, the GL-4 is supposed to make the tranny smoother, but does not seem to be readily available at the mass auto parts stores.

 

Isn't filling thru the breather a pain? I can only fill mine via the fill plug about halfway, then the rest of the way thru the breather.

 

I have a 3" lowered 2WD, i removed the spare and im in the back sittin on the ground trying to fill through breather. lol its painful. next time i'll just destroy that fill bolt and get a new one

 

LOL, mines kinda the opposite. My spare sits in the cargo area behind the rear seat because, well you couldn't fit a 36 under there if you wanted to.
My truck sits high enough that I can sit on the ground comfortably under there. But with the diff pointed upward, you can only get it half full before it comes out the fill hole.

 

Ya I thought of that. If you drain all the old out happy go lucky and then can't get the fill out your kinda up a creek. :lol:

 

^Nice :thumbup:

 

I know