How do I know what transfer case I have? This is the only label I could find. 98 Yukon 4x4.

olliec420 said:

I looked for a tag and I couldn't find it. So are you saying mine does not take AutoTrak II?

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Fless said:

If you have NP8 for an RPO code and the transfer case hasn't been changed to something else, it's the NP246 and does take Auto Trak II.

IIRC the tag is only a couple of inches in diameter.

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What @Fless said, does take Auto-Trak II. I saw in a couple forums where some people said ATF but the vast majority say Auto-Trak II and should be fine.

I wonder what problems may result if use one or the other and should be the other. What does your owner's manual say?

OR VietVet said:

and the transfer case hasn't been changed to something else

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So I better lay eyes on the tag to confirm 100%. Possible it went out and they had it switched.

That paper sticker in your picture says to use transmission fluid, but that seems wrong. Have you tested any of the fluid to see what's in there now? Red would be tranny fluid, blue or some variation of that would be Auto Trak II.

Fless said:

That paper sticker in your picture says to use transmission fluid, but that seems wrong. Have you tested any of the fluid to see what's in there now? Red would be tranny fluid, blue or some variation of that would be Auto Trak II.

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So, it was with one owner for 23 years then another for less than a year. I got it from the less than a year guy last Feb. Havnt driven it much, 2000-something miles. The front end was ******. I just redid it all (drives like brand new) and was about to do all the fluids but this is holding me up. When I was researching before I landed on AutoTrac II for the fluid so I bought it. I also have some Dexron 6 at the house. But then I saw that sticker (and couldn't find the round tag) and wanted to do further research.

What would happen if it was not a 246 and put the AutoTrac in it? Like, is autotrac required for 246 but will work in others that call for ATF?

Fless said:

Not a clue. Maybe @rockola1971 would have an idea?

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You were right. Its uses Autotrac fluid...AKA The blue fluid.

That sticker was put on their by a rebuilder and its wrong. There is no way that Tcase is on its original OEM build from 1998. It could have come from a Dodge truck or meant for one too, they use them and Dodge did spec their own fluid.
Whats throwing you guys off is the difference between a NP246(1998-2002) and a NP246E(2003+). The E means enhanced. In other words, version 2 of the original NP246 from 1998-2002. They are the same unit in general but the NP246E has design upgrades. They are interchangeable with the right input/output shaft to match tranny output shaft spline count and driveshaft yoke spline count which all can vary by year/generation and along with the right sensors and electromagnet that matches your specific PCM configuration.
The AUTO 4wd TCases have clutches in the unit so 4wd can be commanded on and off in an instant by the PCM which is accomplished by an electromagnet.(This works just the like the differentials that have a switch on the dash to turn the diff into a locker) That is why Autotrac fluid is the spec. It has additives specifically for the clutches. ATF fluid does not have the spec additives for Tcase clutches.

Tcases and their fluid type.... https://transfercase.parts/pages/fluid-suggestions-by-transfer-case-type

olliec420 said:

So, it was with one owner for 23 years then another for less than a year. I got it from the less than a year guy last Feb. Havnt driven it much, 2000-something miles. The front end was ******. I just redid it all (drives like brand new) and was about to do all the fluids but this is holding me up. When I was researching before I landed on AutoTrac II for the fluid so I bought it. I also have some Dexron 6 at the house. But then I saw that sticker (and couldn't find the round tag) and wanted to do further research.

What would happen if it was not a 246 and put the AutoTrac in it? Like, is autotrac required for 246 but will work in others that call for ATF?

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Its a NP246. I own (2) NP246E in my 2003 Tahoe LT's. They both look the same externally and quite similar internally.

You can run AutoTrac fluid in any non iron case TCASE. But if you run just regular ATF in an AutoTrac TCASE (NP246/NP246E) you will be taking a chance of premature clutch failure for the AutoTrac function.

rockola1971 said:

You were right. Its uses Autotrac fluid...AKA The blue fluid.

That sticker was put on their by a rebuilder and its wrong. There is no way that Tcase is on its original OEM build from 1998. It could have come from a Dodge truck or meant for one too, they use them and Dodge did spec their own fluid.
Whats throwing you guys off is the difference between a NP246(1998-2002) and a NP246E(2003+). The E means enhanced. In other words, version 2 of the original NP246 from 1998-2002.
The AUTO 4wd TCases have clutches in the unit so 4wd can be commanded on and off in an instant by the PCM. That is why Autotrac fluid is the spec. It has additives specifically for the clutches. ATF fluid does not have the spec additives for Tcase clutches.

Tcases and their fluid type.... https://transfercase.parts/pages/fluid-suggestions-by-transfer-case-type

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Great info!

Yes

To take all the guess work out of all these, "What fluid should I use threads", follow to the letter what the owner's manual says.

I read once that the NP8 actually had multiple suppliers (could’ve just been the new process / new venture thing) but a few of us have gone through this from time to time. I think you’ve already figured it out, but putting a swab into the fill hole would have probably been good advice since that would’ve gotten us to “is the fluid blue or red?”

My 99 burb is now being piloted by my son, and about a month ago I got the call that something was rubbing/ kinda sounds like its coming from one of the front wheels. That was tricky to diagnose for him over the phone (haha) but I probably would’ve been just as stumped in person since it was the dreaded transfer case rub. Fortunately it has been shared on the forums and I put two and two together.

I drop-shipped him a rebuilt t-case (about 700 bucks) and that took care of that. But since I owe the forum universe now, I thought a psa was in order: (0) Mine is blue (1) I think the tcase rub is pretty much inevitable on the GMT 400 NP8. (2) wait and watch for it, because its a high milage thing that makes a noise all its own, and (3) its a pretty easy rebuild, but you could also get in front of it with a sonnax plate saver that protects the case (but to do that you’ve dropped the case and mostly disassembled it anyway)

Happy trails!