How to change F & R Differential fluids

[Hummerguy32]

Hello Everyone Thank You in advance for all replies given!!

I would like to save on money on the changing the rear and front differntials fluids on my 2003 Hummer H2 80,000 miles young. Can anyone point in the right direction on how to start this project which hopefully includes what type of fluid and how much I need, what is involved with changing out the fluids (does it consist of a full flush of the fluid?). Any other concerns please note them for me. Thank you again!

[Hellz]

Tools you will need:

3/8 socket wrench
something to drain the oil in to
5 quarts of 75/90 gear oil

Optional: about 1 ft of 1/2 tubing to make it easier to put in new oil.

on the front diff, use the socket wrench to remove the top fill plug
use the socket wrench to remove lower drain plug
drain in to whatever bucket.
wipe off drain plug ( its magnetized, and will have alot of shavings on it)
put drain plug back in

from diff will take 1.5 quarts ( plus or minus some) fill it till it starts to come out of the fill plug hole.
put fill plug back in and done with the front diff.

rear:

should be a rubber gromet for the fill plug.
pop it off and place your oil pan down.
remove drain plug with socket wrench.
drain oil
replace drain plug, and fill till it starts to come out of the fill plug hole.
maybe about 3 quarts give or take some.

this whole job can easily be done within 15 minutes.

once you have done it, you will laugh at the fact that oil change shops charge $75 to $150 to do that simple job.

[Hummerguy32]

does the gaskets need to be changed on the diff's or do you use rv stuff to spread around the gasket area for a good seal? Also can i do it on a lift or does it have to be on a slight incline/decline for the oil to drain all the way out? Thanx in advance

[Xotik H3]

Can we add the Transfer case to this? Procedure and fuild type/capacity.

[Olfart]

does the gaskets need to be changed on the diff's or do you use rv stuff to spread around the gasket area for a good seal? Also can i do it on a lift or does it have to be on a slight incline/decline for the oil to drain all the way out? Thanx in advance

since you are only going to remove the fill and drain plugs...I Hope:D ....there is no need to seal the gaskets since you won't be splitting the case

[Hummerguy32]

since you are only going to remove the fill and drain plugs...I Hope:D ....there is no need to seal the gaskets since you won't be splitting the case


Sorry I had been confused from seeing you tube how to's on differential's where there where splitting the case open to have the oil drain out.

[Cesardajr]

does the gaskets need to be changed on the diff's or do you use rv stuff to spread around the gasket area for a good seal? Also can i do it on a lift or does it have to be on a slight incline/decline for the oil to drain all the way out? Thanx in advance

i had to replace a washer on the front diff plug, it had a slight drip.
once i had the washer replace all was fine.

[Hummerguy32]

once you have done it, you will laugh at the fact that oil change shops charge $75 to $150 to do that simple job.


I know the dealership wants $125.00 for each. I was thinking what the heck does it take to this myself and you just answered it. Thank You

[Luv2Camp]

I know the dealership wants $125.00 for each. I was thinking what the heck does it take to this myself and you just answered it. Thank You


Please do not take offense to this, but if you were not aware of how to drain and fill a differential, I would use caution before you start to dive in on self repairs. You will REALLY want to be sure that you verify ANY advise you get on working on your H2.... Use the wrong fluid, not fill it up all the way, forget to tighten something and you will REALLY regret not spending the extra cash to have a shop do it.

Now, I am of the opinion that if you want it done right you need to do it yourself and certainly do not want to scare you out of changing your diff fluid as it is really straight forward... I would suggest getting one of the H2 service manuals and ask A LOT of questions

[Stellar]

Great write up by Hellz..Follow his instructions and you'll be fine. It's a simple job, paying a dealership is ridiculous. I went with Royal Purple and couldn't be happier. :beerchug:

[Hellz]

Please do not take offense to this, but if you were not aware of how to drain and fill a differential, I would use caution before you start to dive in on self repairs. You will REALLY want to be sure that you verify ANY advise you get on working on your H2.... Use the wrong fluid, not fill it up all the way, forget to tighten something and you will REALLY regret not spending the extra cash to have a shop do it.

Now, I am of the opinion that if you want it done right you need to do it yourself and certainly do not want to scare you out of changing your diff fluid as it is really straight forward... I would suggest getting one of the H2 service manuals and ask A LOT of questions

the hardest part about changing diff fluids is finding out what gear lube to buy. really, thats the hardest part. i did have to search for it a little on the web, but once i found it and bought it, my wife could have changed the fluids.

there is very very little to mess up with changing the diffs. 2 screw on plugs in the front, and 1 screw on and rubber grommet for the rear.

iirc, i think i used moble 1 with limited slip additive. you will need it, but even if the diff didnt require it, the additive will not hurt being in there.

you could go the highend route and buy royal purple.. i really wanted to, but i didnt want to spend $18.99 a bottle.

again, the hardest part is finding which fluid you use.. otherwise its simple, and no way worth spending the money to have a quick lube place do it for you.

i agree there are alot of thigns that people shouldnt tackle if they arent familiar with changing fluids, but changing fluids isnt one of those if there is a little research done before hand.

hell, most of the things i have done to my H2 i have never done before, and researched the hell out of before i do it..

[HUMMERICH23]

So is it a good idea to do Transmission as well at same time if you?re doing Differentials and T-Case? I am in that position where with 38,000 miles i want to get Fluids switched out to Schaeffer's in my TC and Diffs but was considering doing tranny too. I know the Dealer wants 550 for Diffs, TC, Tranny, but I would only do it if they let me use the fluids i want like Schaeffer. I am wondering if i am better off doing TC/Diffs myself and having a tranny shop do the flush? Is it best to flush or should i just drain out like the 5 quarts and just replace?

[Hellz]

im not going to say it is or isnt a good idea...

the problem is how good of a job you want done?

you can drop the pan, and change the filter, but you are only going to drain about 5 quarts out of the pan. the rest will be in the torque converter, and cooling lines.. thats another 5 to 6 quarts.

im sure if you bring them plenty of the ATF you want, they will put it in for you. you will prolly need to bring enough to flush the system out tho.

so maybe 15 quarts or so......

[Hummerguy32]

So is it a good idea to do Transmission as well at same time if you?re doing Differentials and T-Case? I am in that position where with 38,000 miles i want to get Fluids switched out to Schaeffer's in my TC and Diffs but was considering doing tranny too. I know the Dealer wants 550 for Diffs, TC, Tranny, but I would only do it if they let me use the fluids i want like Schaeffer. I am wondering if i am better off doing TC/Diffs myself and having a tranny shop do the flush? Is it best to flush or should i just drain out like the 5 quarts and just replace?


Thank you again for all the suggestions. The diff's look like no problem w/ my work ethic in the construction industry so i can accomplish though i understand what some may think the dealership should do.

FYI: I did however have the dealership do the tranny flush. I do not have one of those flush machines to really suck all of it out of that area.

[HUMMERICH23]

Do you recall what they charged for just doing Tranny Flush?

[Hummerguy32]

Do you recall what they charged for just doing Tranny Flush?

$124.95 plus tax

State of Pennsylvania

[Hellz]

is that just for the flush, or did they drop the pan and replace the filter too?

[Hummerguy32]

is that just for the flush, or did they drop the pan and replace the filter too?


good question ... not sure I think just the flush.

[Hummerguy32]

Finally changed both the Front and Rear diff. fluids with the Mobile1 you guys recommended (Royal purple sorry just too expensive for me at this time). Project was easy. Thank You all for the help. Used 1.5 quarts in the front and under 4 in the rear. Both of them i filled until it came out the fill hole alot.

[Hellz]

ya RP is some serious $$$

1 pint goes for $18.99 here at most part stores.

now that you did the diffs, the transfer case is just as simple.
just make sure you get the correct fluid.

[pdxrealtor]

FYI I just did the diff fluid changes in my 06 H2 and the front drain/refill is a 13mm/15mm.

There is no rubber fill plug on the rear diff. Both drain and fill are 3/8th ratchet type, same as transfer case.

Thought this might help somebody!

Oh, and also, my rear diff went through more than 3 qts !

[Hellz]

well i have about 1k on my new gears, and was going to change both diffs today while i was working on fixing a squeak on my new brakes....

last weekend i put on new EBC brakes, but didnt have lube for the pads, so i slapped em on anyways... fast forward to day...

the Caliper wouldnt come off on the driver side... so unbolted the brake line to relieve pressure.. it worked out better in the end because i also painted the caliper and bracker while it was off..

since i already had to bleed the brakes anyways, i did the same thing on the pass side... well after painting, and putting the bracket in.. it slipped and landed in the bucket underneath the rotor which splashed brake fluid up in my eye!

well after flushing my eyes for a good while.. decided to call it for the night..

but while i was out.. picked up 6 bottles of RP gear oil @ $21.99 each.. OUCH!

so, will be finising up the brakes and doing the diffs tomorrow..

[pdxrealtor]

That sucks about your eye. I wear sunglasses almost all the time but under the car I didn't , so i could see better. When I was younger I'd do most anything without eye protection. Now that I'm getting older.... For some reason I think about those things. :notallthere:

I was told by a knowledgeable guy, and followed it up with some reading, that redline is far superior gear oil than most. Just like royal purple is for motor oil.

I did all my stuff in redline and it was cheaper. I couldnt believe how much that RP was.

I wish I would have gotten the high temp DT4 for the transfer case, but I just grabbed the regular.

[Hellz]

i think i am just like a bunch of guys here who use RP in almost everything.. Oil, Diffs...i forgot what i used in my T case last time though....

[pdxrealtor]

Sure..

Really, splitting hairs over premium synthetic oils is pointless for most of us. You cant go wrong with RP, REDLINE, MOBILE, etc.. I just felt extra good about the redline because god damn that RP is expensive. To hear the cheaper stuff is superior was a plus! :D

I use RP in my motor.

Hey I see you did gears. Are 4.56s worth it for an h2 with stock size 35s?

[pdxrealtor]

Sure..

Really, splitting hairs over premium synthetic oils is pointless for most of us. You cant go wrong with RP, REDLINE, MOBILE, etc.. I just felt extra good about the redline because god damn that RP is expensive. To hear the cheaper stuff is superior was a plus! :D

I use RP in my motor.

Hey I see you did gears. Are 4.56s worth it for an h2 with stock size 35s?

[Hellz]

dont know about 4.56's, i went with 4.88's

on 37 inch tires..

4.10's tranny would always down shift when crusing at or above 70. on hills or even some acceleration, it would downshift. i felt like i was working the driveline more.

with the 4.88's- quick take offs. tranny isnt working as hard. it will still downshift, but it feels more natural..steeper hills or what not.

today after the diff fluid changes i noticed it was very quiet and smooth.
not saying it wasnt before, but it was break in fluid i had in it with just a little over 1k miles on the new gears. everything felt smooth... just only was i can describe it. on the plus side, i gained just over 1 mp from the regear.. so now im at 9.9 mpg.. was at 8.8 on stock gears.

if your running stock 35's, i dont see a reason to regear to 4.56s. i guess there are benefits to quicker take offs, and maybe some extra MPG.. someone else might be able to chime in about it.

If you plan on going bigger tires.. then yes, i wouldnt hesitate and regear.

im thinking of moving up to 38's... i just dont want to do a lift.. well i will do new T keys, but no body lift. I think i can do 38's, but i might still stay at 37's..

If you know anyone selling BFG M/T KM2 37 inch tires, let me know. i have 1 brand new one, just need 3 more..tho, might go with the Toyo's if i cant find a good deal

[pdxrealtor]

Don't plan on going up in tire size... I'm actually looking to get rid of my M/Ts and go with an A/T.

I drive to the mountain a lot in the winter, and I never ever mud. Don't know what I was thinking when I got the M/Ts..