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

[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


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