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.

 

[brasil]

whenever I buy a used car...I am changing all fluids...from coolant to brakes from engine to tranny...
then I know exactly what is going on.. also the brand ( I am a Amsoil fan also ) is important to me.
The reward is...a good running car. That I can trust in..

Greetings Juergen

 

[mals]

Question about the fill level of the rear differential:

My manual says the appropriate level of the 75w-90 in the rear case is 5/8" to 1-5/8" below the bottom of the fill hole.

Every how-to write up I've read and video I watched on YouTube specifically about GMT800s shows people filling the differential until it runs out the fill hole.

Is there something special about my AWD setup or is everyone overfilling theirs out of convenience?

 

[Denali2k8]

Question about the fill level of the rear differential:

My manual says the appropriate level of the 75w-90 in the rear case is 5/8" to 1-5/8" below the bottom of the fill hole.

Every how-to write up I've read and video I watched on YouTube specifically about GMT800s shows people filling the differential until it runs out the fill hole.

Is there something special about my AWD setup or is everyone overfilling theirs out of convenience?

The 2nd. Typically

 

[mals]

The 2nd. Typically

OK, that's what I figured, but I wanted to make sure there wasn't a TSB that advised the fluid level should be raised to the fill hole. I take it you take the time to slowly add the fluid and periodically check towards the end to verify the level?

 

[brasil]

There is a plastic sticker on the diff carrier close to the fill plug. It says keep the level 15 to 40 mm below the filling hole - if you use Syntetic oil. Also friction modifier is NOT recommended

Hope that helps

Greetings Juergen


BTW...there are a lot of stupid videos on YT

 

[mals]

BTW...there are a lot of stupid videos on YT

Thanks for the confirmation. I agree, and I would not trust any one video explicitly, but as a collective whole when you watch several on the same topic you can find the core of what you need to know.

I grew up working on old air cooled Volkswagens, and this is my first large V8 american vehicle. I have decent mechanical skills and know how, but it is nice to review the procedures others use in tackling a problem/project/repair, and then apply my skills to that knowledge.

 

[HiHoeSilver]

Thanks for the confirmation. I agree, and I would not trust any one video explicitly, but as a collective whole when you watch several on the same topic you can find the core of what you need to know.

I grew up working on old air cooled Volkswagens, and this is my first large V8 american vehicle. I have decent mechanical skills and know how, but it is nice to review the procedures others use in tackling a problem/project/repair, and then apply my skills to that knowledge.

What Volksies did you have?

 

[mals]

What Volksies did you have?

I had a 1966 Beetle that I bought out of a field when I was 16 for $100 that I restored to show car quality.

A 1974 bus that was my daily driver in high school that I pieced together using parts and drive train from a wrecked 1977.

A 1979 bus that was my daily driver through college.

An early '70s Karmann Ghia that I fixed up for my sister when she got her license.

A 1972 411 Wagon that I fixed up for my girlfriend (now wife) so she could have something to bring to the VW shows when I went with my '66 Beetle. I told her she could pick whatever she wanted, and I'd fix it up for her. She settled on one of the lowest production models they ever built. We ended up finding one in Arizona and having it shipped to the east coast.

There were a few beetles along the way that I bought cheap, fixed and flipped through high school, but the list above are the ones that stand out. We sold the 411 and the Beetle for the down payment on our first house, so I guess it worked out.

 

[mals]

I completed the fluid changes last night.

The rear diff fluid looked fairly clean, and had been serviced before at some point. Only a little metal dust on the magnet. The rear cover was pretty beat up, rusty, and had most of a tube of RTV and pieces of an older gasket on it so I decided just to pick up a replacement cover at a local auto parts shop. It was raw steel so I gave it a coat of clean metal primer, and two coats of satin black.

The front diff appeared to have never been serviced in the 160K on the vehicle. The fluid was dark and opaque. The magnet was covered in a thick layer of fuzzy metal shaving, but no metal chunks or chips.

The transfer case fluid looked clean, but the big surprise was about a quart of extra fluid came out when I opened the fill port before draining the case. A little research suggests that I have a bad input shaft seal on the transfer case and ATF from the transmission is making its way in.

I always check the ATF level before I head out to tow (it's on our departure checklist) and have never seen the level drop. I'll keep an eye on it now since the level in the case is where it should be, I'll see how long it takes to loose a quart of ATF.

This may delay me servicing the transmission. I was planning on pumping out all the fluid and doing a full exchange over to the Amsoil Dex VI compatible ATF, but don't want to do that since the transfer case should not get Dex VI in it.

Is this something that should be a top of the list fix, or just service the trans with Dex III Amsoil and keep an eye on the levels until something larger fails in the trans and then get everything rebuilt at once with upgraded parts?

 

[95escahoe]

I completed the fluid changes last night.

The rear diff fluid looked fairly clean, and had been serviced before at some point. Only a little metal dust on the magnet. The rear cover was pretty beat up, rusty, and had most of a tube of RTV and pieces of an older gasket on it so I decided just to pick up a replacement cover at a local auto parts shop. It was raw steel so I gave it a coat of clean metal primer, and two coats of satin black.

The front diff appeared to have never been serviced in the 160K on the vehicle. The fluid was dark and opaque. The magnet was covered in a thick layer of fuzzy metal shaving, but no metal chunks or chips.

The transfer case fluid looked clean, but the big surprise was about a quart of extra fluid came out when I opened the fill port before draining the case. A little research suggests that I have a bad input shaft seal on the transfer case and ATF from the transmission is making its way in.

I always check the ATF level before I head out to tow (it's on our departure checklist) and have never seen the level drop. I'll keep an eye on it now since the level in the case is where it should be, I'll see how long it takes to loose a quart of ATF.

This may delay me servicing the transmission. I was planning on pumping out all the fluid and doing a full exchange over to the Amsoil Dex VI compatible ATF, but don't want to do that since the transfer case should not get Dex VI in it.

Is this something that should be a top of the list fix, or just service the trans with Dex III Amsoil and keep an eye on the levels until something larger fails in the trans and then get everything rebuilt at once with upgraded parts?

I had the same leaky seal on my Escalade, I had a local shop replace it, I'd see how much it's leaking and go from there if it's real bad get it taken care of asap if not you could always just keep it topped off and wait till something in the tranny goes, I opted to do it because it shifts good and no other issues otherwise and to risk any damage to the transfer case


Sent from my iPhone using Tapatalk