# Transer case and front diff fluid change



## ABES (Jun 10, 2007)

So I am trying to get my truck ready for 8 hours of towing I have coming up and the only things I have left on my list are transfer case fluid change and front diff fluid change.

Should I just use standard dex/merc 3 ATF for the transfer case? How many quarts?

I am assuming the front diff uses regular 80W90 gear oil?

Thanks for the help guys:waving:


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## ABES (Jun 10, 2007)

Also anybody know what size allen/hex wrench I need to remove the filler and drain plugs on a NP243 T case


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## B&B (Nov 4, 2006)

You'll need a little over 2 qts for the T-case ABES. You can use regular Dex III ATF which was the factory recommended fluid...but if you do I also highly recommended adding a pint of Lucas oil stabilizer in addition to the ATF to prevent a common condition that these T-cases suffer from called "misting". Basically the T-case (with all its spinning internal parts) will actually vaporizes the ATF due to its thin consistency, causing it to slowly over time be expelled out the vent tube as a vapor and lowering the fluid level to dangerous levels. It never actually leaks on the ground since its in a vaporous state so the owner never realizes its low on fluid until its too late. Many 241/243 (including Dodge 231/241's as well) T-cases have been ruined due to this condition. The aftermarket finally changed the fluid recommendation on these specific cases at maintenance interval time to include adding a 50/50 mix of Dex III ATF AND 10W-30 motor oil in order to thicken up the viscosity a little to combat the misting problem, which is why adding the Lucas is a smart idea. Synthetic ATF is also highly recommended if you have the extra funds for it. Royal Purple, Amsoil, Redline and Mobile all make good quality synthetic ATF if you want to go that route. 

You'll need a 30 mm socket for the fill and drain plugs. Tip: Loosen the fill before removing the drain to be sure it'll come out. If you cant get the fill loose you dont want the T-case empty BEFORE you find that out...happens alot to guys.

The front diff you can use either regular old dino 80W-90 gear oil (GL5 or above rated)..or switch it over to synthetic gear oil as well. You'll need a little over 2 qts. Lucas in there as well if your a belt and suspenders kinda guy. You'll need a 13mm and 15mm socket for the fill and drain on the diff.


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## ABES (Jun 10, 2007)

Thanks for the info B&B I will go the synthetic route then.

The only thing I am confused about here is the drain and fill plugs for the T case.I didnt see any 30mm bolt heads on the case. I took some pictures of what I thought were the drain and fill plugs but they look like they have hex head. None of the wrenches I had where big enough. Im still not even sure as to why one of the previous owners would swap out the plugs.

Thanks again for the help


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## B&B (Nov 4, 2006)

Some 241/243's did use countersunk allen plugs for the drain and fill in the later years (like the current 261/263's use)...looks like yours is one of them. _*Should*_ be a 5/8.


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## ABES (Jun 10, 2007)

good deal Ive got it draining right now I went over to my bosses shop and a 10 mm worked great. The fluid that was in there was blue so I am assuming the previous owner put some type of synthetic in there?? having push button 4wd shouldnt matter what type of fluid i use should it? I might just use reg dex 3 as i found a bottle of lucus around my garage.

Thanks again B&B


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## B&B (Nov 4, 2006)

Sounds like someone used Auto-Trac fluid in it at some point which isn't needed in the 241/243's. Guys think that any GM push button T-case is supposed to use the special Auto-Trac fluid but it's actually only needed for the actual "on demand" Auto-Trac 246 T-cases that have a full time 4WD position... like the newer bodied 2000 K2500's, Suburbans/Tahoe's and '99-up K1500's

Doesn't hurt anything...and will actually help with the misting issue. If you have the Lucas already, use the ATF.


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## ABES (Jun 10, 2007)

well with your help B&B I got the truck ready to go that lucus is really thick stuff I can see why you would reccomend it. The truck has fresh oil, fresh trans fluid, fresh T case fluid, fresh front and rear diff fluid, and she is all greased up should be ready for towing my friends jeep for several hundred miles in a couple weeks. 

Thanks again I really appreciate your help


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## grandview (Oct 9, 2005)

Don't forget to put gas in it before you go!


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## ABES (Jun 10, 2007)

grandview;561962 said:


> Don't forget to put gas in it before you go!


lol thats the last and most dreaded thing on the list


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## Milwaukee (Dec 28, 2007)

gas would cost you almost $600. If your truck average 13 mpg.

It seem that we can't do anything until someone would pay me for gas.

i will check u joint, rear axle's oil, and tires.

My truck have bad tires but I am lucky it last until I replace because I was afraid drive with very weather rot tires that look ready to give up on Highway.


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