Servicing Transfer Case and F/R Differentials - Fluid Recommendations?

[mals]

I am planning on tackling the service on my transfer case and both differentials in the near future. After checking my owner's manual, and a little additional research, this is what my 2005 AWD Yukon with a NR3 transfer case originally required:

Transfer Case - DEXRON III-H
Front Differential - SAE 75W-90 Synthetic
Rear Differential - SAE 75W-90 Synthetic
​

I have also read that while modern DEXRON VI is backwards compatible with automatic transmissions that originally required DEXRON III, it should not be used in transfer cases or manual transmissions that originally spec'd DEXRON III.

It seems that the safest path is to use a DEX/MERC ATF oil that meets the DEXRON III-H spec. Would there be any benefit to sticking to a mineral oil based DEX/MERC like Pennzoil DEX/MERC ATF, or does it make sense to transition over to a synthetic version like Mobil 1 Synthetic ATF?

As for the differentials, my Yukon's main use is to tow our travel trailer. I've seen it recommended in various forums that many people change over to 75W-110 or even 75W-140 for vehicles that see heavy use or extended towing.

Any guidance on what you have done, and how that choice has performed would be welcome.

 

[Denali2k8]

Amsoil. Plug your vehicle in and use what they recommend.

http://www.amsoil.com/AmsoilGarage/...page.aspx?url2=2005+GMC TRUCKS+YUKON DENALI+U

 

[Granprixfan]

I second what Denali2k8 said
AMSOIL
Assuming nothing is suspect, like metal in oils when you drain 'em....
Change these fluids once and "ferget'bout it"

 

[mals]

Amsoil. Plug your vehicle in and use what they recommend.

I second what Denali2k8 said - AMSOIL
Assuming nothing is suspect, like metal in oils when you drain 'em.... Change these fluids once and "ferget'bout it"

So looking at the specs and change interval for the Amsoil Severe Gear SAE 75W-90, would this really be a once an most likely done service for the differentials?

I was planning to swap out the rear diff cover for one with a drain plug and use a lube locker G850 gasket. That way the cover would have a good permanent seal, and future fluid changes would be much easier. Even if I considered my usage "severe" Amsoil's change interval would drop from 100,000 miles to 50,000 miles. Considering I only put 5,000 on it in the past year, it may not be worth the cost of the diff cover to make a job easier in 10+ years.

Do either of you have an Amsoil Preferred Customer account? If looks like if I sign up and give them your user ID as a referral you'll get a credit for it.

 

[Denali2k8]

So looking at the specs and change interval for the Amsoil Severe Gear SAE 75W-90, would this really be a once an most likely done service for the differentials?

I was planning to swap out the rear diff cover for one with a drain plug and use a lube locker G850 gasket. That way the cover would have a good permanent seal, and future fluid changes would be much easier. Even if I considered my usage "severe" Amsoil's change interval would drop from 100,000 miles to 50,000 miles. Considering I only put 5,000 on it in the past year, it may not be worth the cost of the diff cover to make a job easier in 10+ years.

Do either of you have an Amsoil Preferred Customer account? If looks like if I sign up and give them your user ID as a referral you'll get a credit for it.

I do.

Customer (ZO) #: 5001684


Idk if I would go thru the hassle of changing the cover. It's not that hard to do without a drain plug. Depends what you wanna spend you $$ on

 

[mals]

I do. Customer (ZO) #: 5001684

Order placed for 4 quarts of 75W-90 and 3 quarts of Signature Series Multi-Vehicle Synthetic ATF with your ZO as the referring customer. Thanks for pushing me in the direction that I knew I should go. I was just hoping to use something local to get the work done this weekend. I'll see if I can squeeze in the service before we head out for our first trip towing Memorial Day weekend, if not I'll do it in June when we get back.

 

[Denali2k8]

Order placed for 4 quarts of 75W-90 and 3 quarts of Signature Series Multi-Vehicle Synthetic ATF with your ZO as the referring customer. Thanks for pushing me in the direction that I knew I should go. I was just hoping to use something local to get the work done this weekend. I'll see if I can squeeze in the service before we head out for our first trip towing Memorial Day weekend, if not I'll do it in June when we get back.

I put amsoil in everything I own. 2 sportbikes, a couple harleys (not mine), Denali, Grand Cherokee, etc etc etc. I swear by it. If it can protect my GSXR which is a high reving inline 4 sportbike for 50k miles, I trust it in everything.

 

[DenaliEd]

Looks like I'm late to the party, but I see you got pointed in the right direction!!! You should also consider changing the ATF and filter in the trans, and your truck could probably use a brake fluid flush as well, especially if you're going to be towing with it. Brake fluid is the #1 most overlooked fluid in a vehicle...

 

[mals]

Looks like I'm late to the party, but I see you got pointed in the right direction!!! You should also consider changing the ATF and filter in the trans, and your truck could probably use a brake fluid flush as well, especially if you're going to be towing with it. Brake fluid is the #1 most overlooked fluid in a vehicle...

Thanks. Yes, the trans service is on the to-do list, but I've checked and the current fluid is bright and clean looking so I feel ok with it for right now. The brake fluid also looks clean, and I know the dealer replaced the rear brakes and calipers when I bought it, so it looks like they at least fed in some new fluid at that time. A NNBS front brake upgrade is on my list as well, and I am planning to do a full bleed and flush of the system at that time. Hopefully that will be this summer or fall.

 

[DenaliEd]

Good deal. As long as you're on top of it.