Transmission gets Mercon III or VI? What about the transfer case?

[WildernessJeep]

I'm confused.

2005 Yukon Denali, AWD with 110,000 miles on it.

I am trying to do the transmission flush, as per ScottyBoy's write up. Seems pretty straight forward, and in his writeup he uses Mercon IV (6).

Did the vehicle come with Mercon 3, and he is upgrading to 6, or has it had synthetic all along? Is one better for this vehicle? The auto parts guy tried to sell me Mercon 3, but I understand there is a tech bulletin from GMC for some VIN's to upgrade to Mercon 6, but not all.

This is all before I start on the transfer case, which I assume gets the same fluid as the transmission.

Opinions?

 

[Sasquatch]

Mercon is for use in fords. Dexron is GM.


I`d stick with dexron. I have an 05 yukon and when i changed my fluid i used dexron 6. 10,000+ miles since with no problems. I changed mine at around 55k miles.

 

[WildernessJeep]

Mercon is for use in fords. Dexron is GM.


I`d stick with dexron. I have an 05 yukon and when i changed my fluid i used dexron 6. 10,000+ miles since with no problems. I changed mine at around 55k miles.

Most fluids are both, I just said Mercon because it was easier to type than the whole Mercon/Dexron word.

Transfer case? 3 or 6??

 

[BRUTUS_T_HOG]

3 or 6 will be fine in the transmission.

If your vehicle has auto 4wd it requires auto trak 2 fluid, do not put atf in

 

[WildernessJeep]

3 or 6 will be fine in the transmission.

If your vehicle has auto 4wd it requires auto trak 2 fluid, do not put atf in

How many quarts do I need? Two??

 

[BRUTUS_T_HOG]

I would get 3qt. The t-case will take just over 2 qts

 

[Wake]

3 or 6 will be fine in the transmission.

If your vehicle has auto 4wd it requires auto trak 2 fluid, do not put atf in

4wd is not the same as AWD.

The 05 doesn't use AT2 fluid, it uses Dex3-E ATF.

 

[WildernessJeep]

4wd is not the same as AWD.

The 05 doesn't use AT2 fluid, it uses Dex3-E ATF.

See? That's the problem. Everyone has a different idea about what fluid to use. What is the ultimate source? Where would I go for the final authority and answer?

 

[BRUTUS_T_HOG]

Ok to clear it up I just took the time to look in the factory service manual. AWD takes dexron 6. Auto 4wd takes auto trak 2.

The ultimate source would usually be the owners manual

 

[WildernessJeep]

Ok to clear it up I just took the time to look in the factory service manual. AWD takes dexron 6. Auto 4wd takes auto trak 2.

The ultimate source would usually be the owners manual

I dont' have one. Dextron 6 it is. Thanks for the help!!

R

 

[Wake]

I dont' have one. Dextron 6 it is. Thanks for the help!!

R

No, not Dex6, it's different than Dex3H.

I couldn't find the reference I had prior, but here is one from GMTechLink:
https://gmspecialservicetools.spx.com/Media/Common/Documents/may2007.pdf

"Precaution: DEXRON-VI in Manual Transmissions
When DEXRON-III is indicated as the fluid fill for manual transmissions and transfer cases, DO NOT use DEXRON-VI. Instead, use GM Manual Transmission Fluid p/n 88861800 in these components.

TIP: Refer to PIP3836B (Feb. 2007).
If the manual transmission or transfer case indicates use of DEXRON-VI, then, of course, it should be used."

 

[WildernessJeep]

No, not Dex6, it's different than Dex3E.

I couldn't find the reference I had prior, but here is one from GMTechLink:
https://gmspecialservicetools.spx.com/Media/Common/Documents/may2007.pdf

"Precaution: DEXRON-VI in Manual Transmissions
When DEXRON-III is indicated as the fluid fill for manual transmissions and transfer cases, DO NOT use DEXRON-VI. Instead, use GM Manual Transmission Fluid p/n 88861800 in these components.

TIP: Refer to PIP3836B (Feb. 2007).
If the manual transmission or transfer case indicates use of DEXRON-VI, then, of course, it should be used."

The plot thickens. I asked the GM (chevy) dealer, and not only did they not have a clue, even after asking the techs, they apparently have been putting Dex 6 in everything (probably because it is more expensive). Considering that my truck is out of warranty, and if the wrong fluid eats the transmission/transfer case, I'm SOL, I want to make sure that I put the right stuff in.

Your link says that Dex 6 is not appropriate, and that I should use Dex 3E. What is the "E" designation?

R

 

[Wake]

The plot thickens. I asked the GM (chevy) dealer, and not only did they not have a clue, even after asking the techs, they apparently have been putting Dex 6 in everything (probably because it is more expensive). Considering that my truck is out of warranty, and if the wrong fluid eats the transmission/transfer case, I'm SOL, I want to make sure that I put the right stuff in.

Your link says that Dex 6 is not appropriate, and that I should use Dex 3E. What is the "E" designation?

R

Sorry I had a typo in my post, it's Dex III-H fluid, not E. As far as I know the H describes the additive package in the fluid. When GM specs the parts, trans, diffs, transfer cases, engines, etc they spec them based on the fluid used at the time. So they spec'd it on the Dex 3H that was available during development.

Dex 6 is newer and you would think better, but from what I've been able to find out about it, was the viscosity was too low for use as a replacement in older Dex 3 applications. There are a lot of links to sort through on the web so finding good information is a little difficult.

Since Dex 3 is hard to find nowadays as GM doesn't license it anymore I had to look around a little bit and read a lot of labels. I ended up with Mobil 1 synthetic ATF, the label states it met the Dex III-H specification so that was what I ended up putting in. I found it at either Walmart, Advance Auto, or Autozone, I can't remember which store as it was over a year ago. One of my local chain stores carried it though.

Since you don't have a manual you might search for "05 Denali owners manual pdf" you should find a link to GM's FTP website and still be able to get it from GM, then you'll have all the specs for the fluids, maintenance schedule, feature programming, etc.

 

[Hacker-Pschorr]

The ultimate source would usually be the owners manual

+1

I've been searching the forum since my 2003 Denali XL is due for a full fluid change.
AFAIK the 03 and 05 uses the same fluids.

My manual states:
Auto Transmission: Dexron - III
Front and Rear Axle: 75w-90 Synthetic
Transfer Case: Dexron - III

Dex 6 is newer and you would think better, but from what I've been able to find out about it, was the viscosity was too low for use as a replacement in older Dex 3 applications. There are a lot of links to sort through on the web so finding good information is a little difficult.

Red Line has their D4 and D6 transmission fluid, both listed as compatible for Dexron III.

Looking at the specification, the D4 is thicker:
http://www.redlineoil.com/product.aspx?pid=115&pcid=9
http://www.redlineoil.com/product.aspx?pid=51&pcid=9

Which is why I'm going with D4 in my Denali.