Diff Fluid change for 2004 Suburban? 75w-90 75w-140?

[jeff in co]

2004 Yukon XL, 8.1L, 3/4 ton.

I'm going to change my diff fluids and my transfer case fluid in the next few days so I look in the Owner's Manual and see:

Front: 80W-90 Dino oil
Rear: 75W-90 Synthetic
Transfer case: Auto Trak II

I was originally going to just change the front and rear with 75W-90 Synthetic and be done, but I decided I'll just swing by the Dealer and see what they recommend.

Well, I get in there and the service writer starts recommending 75W-140 Synthetic, for the front and rear differentials, and then a 75W-80 Synthetic for the transfer case.

He said the 75W-80 is more expensive but does a better job. I asked a better job than what. He just said it was better and he uses it in his personal vehicle. ($31/Qt vs. $10/Qt of Auto Trak II)

So now I'm more confused after visiting the dealer than before!

Why would he specify something so much more different than the owner's manual? Or is it really that different?

He also said I should add the limited slip additive in the rear, regardless. It just helps the performance. I told him I had the G80 option and didn't think it applied. He said it would just work better and they always add it in their oil changes regardless. Seems unnecessary.

Any oil guru's out there?

 

[jeff in co]

They are recommending "BG Synthetic Oil" for all the oils specified above.....but I've never heard of them. I was just going to use Mobil or Royal Purple (probably Mobil if cheaper).

 

[miniwally]

I use GM "grape Juice" It really does smell like grapes. I think it's a 75-90 synthetic for the duramax trucks. Front and rear, no additives needed. You can also find it online from places like Merchant Automotive.

Then I don't know about the transfer case, I use automatic transmission fluid in mine but that is what the book calls for.

 

[63chevyll]

You will be ok with 75w 140 in both diffs. You don't need the posi additive unless you have a posi.
They will always recommend because they don't always pull the cover to look at the carrier. And most of the service guys doing the lube stuff don't even know what the hell a limited slip is.

As far as transfer case. IF its auto, as in has an auto mode then you need autotrac fluid for the clutches. If not then and dex 3, 4, 5 or 6 will be fine. Pretty sure 5 and 6 are synthetic

 

[jeff in co]

I'd rather go 75w-90 as it's cheaper.....unless there is some other reason to change.

Yaa, auto 4wd so auto trakII.

That totally makes sense on the additive....they were going to just suck it out without pulling the cover (typical).

 

[6.2Blazer]

It's downright scary that a GM service writer recommended 75W-90 in an Autotrak t-case. They don't even like regular ATF (in which every t-case uses) and can't imagine what would happen if you put gear lube in it. Though I shouldn't be surprised as one of the service writers at the GM dealer in my old town probably couldn't tell the difference between windshield washer fluid and engine oil.

Heck, GM hasn't made a transfer case that needed gear lube since probably the early 80s.

 

[63chevyll]

I'd rather go 75w-90 as it's cheaper.....unless there is some other reason to change.

Yaa, auto 4wd so auto trakII.

That totally makes sense on the additive....they were going to just suck it out without pulling the cover (typical).

Really for the cost increase on 4 quarts and changing every 50,000 miles or so.doesn't bother me.

Just today I.bought valvoline 75 140 synthetic for $14 a quart.

But its still a toss up 80w90 or 75w140. The 75w140 is suposed to help with fuel mileage

 

[jake 03]

75w-90 in the front and rear diffs,Autotrac II ONLY in the transfer case.
You follow the advise of that idiot and you will be needing a tcase shortly.
The only case it may be ''ok'' to put 75w-90 is the full time AWD case in the Denali and Cadillac suvs because the T3 unit is all gear driven.

 

[jeff in co]

Really for the cost increase on 4 quarts and changing every 50,000 miles or so.doesn't bother me.

Just today I.bought valvoline 75 140 synthetic for $14 a quart.

But its still a toss up 80w90 or 75w140. The 75w140 is suposed to help with fuel mileage

Well, I went to the other Chevy dealer and they also use 75w 140 in the front and rear.

I then went to the GMC dealer, and they said 75w 90.

Both said Auto Trak II so I don't know what that first guy was thinking.

Brad, you are the first to tell me any compelling reason to change to the 75W 140 as being better mileage. No one at any of the dealerships could really tell me the reason between the two different weights. Other than it's easier for them to just use one weight for ALL vehicles across the board.

Anyways, I did pick up 2 quarts of Auto Trak II at $8 each.

 

[63chevyll]

I actually learned something. I didn't think a 3/4 ton of that year had the auto track option. Thats cool to know.

Also, pisses me off how people sell you crap and they don't know anything about it nor give you a true explanation why

 

[jeff in co]

I actually learned something. I didn't think a 3/4 ton of that year had the auto track option. Thats cool to know.

Also, pisses me off how people sell you crap and they don't know anything about it nor give you a true explanation why

So true. He was a young buck too. We went to the parts counter and they pulled the different 2 fluids. When I asked why should I change, he really couldn't say anything tangible .....just its better.

Yea, love the truck. 8.1L, auto 4wd, 4wd hi, 4wd low...and of course 2wd.

 

[diesel4me]

Something I've noticed at parts stores lately,especially ones like Autozone and similar box stores,if you ask for a spec on which lube to use,their computers DO list the stuff thats reccomended,but it also puts THE most expensive lubricant available at the top of the list!--and the counter guys are trained to MAKE MONEY ,so of course they will say "this is what is reccomended"....usually a high dollar synthetic,which is totally un-nessasary in an old truck thats had 100+ thousand miles put on it with regular dino lubes...............................................................................................................................................................................................................if you tell them to look DOWN the list,you'll see the usual gear oil or tranny fluids that are just as "good" for much less $$$$$$....they'll also steer you towards the most costly "platinum" spark plugs,the most expensive brake pads & rotors, and other things you DONT need or want on an old truck too,if you let them....buyer beware!.....I dont like the fact new vehicles now need some "special" lubes to keep things from self destruction,like the "Syncro" tranny lube that goes for 15 bucks a quart...and can only be found at DEALERS...can you say "m-o-n-o-p-o-l-y boys and girls??...

 

[dremu]

Right. Because auto parts stores are not businesses, run to make money; they are a volunteer service for enthusiasts, and their profitability to the shareholders is of no consequence.

Of course they're going to try to make money -- if they didn't, they go out of business. It's how the world works. As consumers we must be eagle-eyed to sales tactics, whether from the (essentially untrained) counter monkey or the corporate honchos.

Caveat emptor.

-- A

 

[diesel4me]

I'm not bashing the counterpersons,I WAS one for 20+ years at several auto parts stores...but I didn't "push" items to people that didn't need them,I found out quickly if someone felt they got screwed because they bought something they didn't really need at someone elses advice,that soured them from wanting to come back and buy other parts or fluids,and thats not good for bussiness...my bosses agreed for the most part,while its nice to make a healthy profit,if you only do it ONCE and the customer feels cheated and goes elsewhere after that,you haven't "made" anything,really..............................................................................................................................................................................................Of course things today aren't like they were 20 years ago--now its all about selling the most expensive stuff as much as possible,and no stores want to look up parts if you dont have an "application"...when I worked parts counters,you were expected to NOT let that customer leave without parts,even if it meant spending a half-hour looking thru catalogs and opening boxes..today they just say "sorry--our computer doesn't list parts unless you can tell me what it came off of--NEXT!"....if you go in a store today not knowing what you need,you can rest assured they'll sell you the most costly stuff as far as fluids and common tune up parts go...