HOW TO: Change Transfer Case Fluid

[2003KJ]

The instructions are the same for both the Np231 and Np242 transfer cases. I apologize for the bad shots...having a hard time getting it from the .pdf document to a program that would actually let me convert the image to something useful.

Np231 (Command-Trac)

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Np242 (Selec-Trac)

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To drain, first remove the fill plug (that way you're positive you can get new fluid back in there...nothing like removing the old fluid only to find out the fill plug is stuck on). Once the fill plug is off, remove the drain plug and allow fluid to drain out. Once old fluid has drained, re-install the drain plug, and fill the t-case back up with the appropriate fluid, via the fill hole, until it reaches the bottom of the fill hole (or begins to run out).

BOTH the Np231 and Np242 require Mopar ATF +4 type 9602 Automatic Transmission Fluid. You can probably get away with using another type of ATF +4, but i probably wouldn't risk it with something as important as the transfer case. Remember to get ATF +4....not +3 or anything else.

 

[N / A]

thanks dude

 

[2003KJ]

thanks dude

Sure thing buddy O

 

[TopShapeCabby]

Is there synthetic oil available for the transfer case?

If so, is it worth it?

 

[Eddo]

These t-cases doesnt have any clutch pack or solenoids like the transmission so ATF+4 is not really necessary. You can use any high-quality ATF or synchromesh fluid. ATF+4 is a good synthetic fluid, but was just specified for continuity in dealer servicing. I replaced mine with a synthetic synchromesh fluid 25k ago and haven't had any problems. These are the same t-case Jeep has been using for years. Alot of people even run a light weight motor oil in them.

 

[2003KJ]

These t-cases doesnt have any clutch pack or solenoids like the transmission so ATF+4 is not really necessary. You can use any high-quality ATF or synchromesh fluid. ATF+4 is a good synthetic fluid, but was just specified for continuity in dealer servicing. I replaced mine with a synthetic synchromesh fluid 25k ago and haven't had any problems. These are the same t-case Jeep has been using for years. Alot of people even run a light weight motor oil in them.

Interesting.....i've always heard the t-cases are picky about the proper fluid in them....

 

[Eddo]

These t-cases doesnt have any clutch pack or solenoids like the transmission so ATF+4 is not really necessary. You can use any high-quality ATF or synchromesh fluid. ATF+4 is a good synthetic fluid, but was just specified for continuity in dealer servicing. I replaced mine with a synthetic synchromesh fluid 25k ago and haven't had any problems. These are the same t-case Jeep has been using for years. Alot of people even run a light weight motor oil in them.

Interesting.....i've always heard the t-cases are picky about the proper fluid in them....

The, transmission can be quite picky. Alot of people confused the two since they sound similar are are right next to each other. The t-case is nothing more than a set of gears that directs power to the two drive shafts with a low range. Not much more than a differential.

An automatic transmission is much more complex with wet clutchs, solenoids, pistons, that all need to be functioning in perfect unison for quality shifting. Small chance in the coefficent of friction and viscoity can have an effect on the transmission shift quality. That is why the computer needs often needs to be re-train when you just change the fluid.

Also the t-case is not electronically or automatically controlled in anyway. All done with the shift of the level. The new electric, slip detection, automatic t-case are a lot more complex and the exact specified fluid is probably more critical. But, t-cases in our KJ, TJ, and most older jeeps are simple old mechanical t-cases.

 

[2003KJ]

These t-cases doesnt have any clutch pack or solenoids like the transmission so ATF+4 is not really necessary. You can use any high-quality ATF or synchromesh fluid. ATF+4 is a good synthetic fluid, but was just specified for continuity in dealer servicing. I replaced mine with a synthetic synchromesh fluid 25k ago and haven't had any problems. These are the same t-case Jeep has been using for years. Alot of people even run a light weight motor oil in them.

Interesting.....i've always heard the t-cases are picky about the proper fluid in them....

The, transmission can be quite picky. Alot of people confused the two since they sound similar are are right next to each other. The t-case is nothing more than a set of gears that directs power to the two drive shafts with a low range. Not much more than a differential.

An automatic transmission is much more complex with wet clutchs, solenoids, pistons, that all need to be functioning in perfect unison for quality shifting. Small chance in the coefficent of friction and viscoity can have an effect on the transmission shift quality. That is why the computer needs often needs to be re-train when you just change the fluid.

Also the t-case is not electronically or automatically controlled in anyway. All done with the shift of the level. The new electric, slip detection, automatic t-case are a lot more complex and the exact specified fluid is probably more critical. But, t-cases in our KJ, TJ, and most older jeeps are simple old mechanical t-cases.

Interesting to know as i'm gonna be changing mine for the first time before too long.

 

[bgjeep]

What size allen wrench is needed for the fill/drain plugs?

 

[Vtolds]

How much approximate fluid is needed to do this change? I am just past 60,000 and I thinking I should probably do it before next winter.

 

[2003KJ]

NV231 - 1.4L (2.95 pts)

NV242 - 1.6L (3.4 pts)

From the 2003 FSM...but it will be the same for all years as the same cases were used.

 

[LibertyOrDeath]

I just did this and found the easiest way to re-fill the T-case was by taking filler cap off of a quart of gear oil and putting it on the trans fliud bottle. So much easier that trying to use a funnel.

What size allen wrench is needed for the fill/drain plugs?

10MM

 

[SpankyKJ]

I just did this and found the easiest way to re-fill the T-case was by taking filler cap off of a quart of gear oil and putting it on the trans fliud bottle. So much easier that trying to use a funnel.




10MM

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how to change transfer case fluid w/pics:
http://jeep.us41.org/transfercase/index.html

 

[Luke]

Thanks guys! Awesome info and pics!

Just had my 05 in for the "peace of mind" service at my local dealer (gotta be a joke in there somewhere) and they recommended that I have the transmission and t-case fluids changed before too long. I am at 58,000k (36k miles) and although this seems early to me I have no idea what this girl went through before I got her 2 weeks ago. At least I can tackle the t-case myself and save 50 bucks. The $160 for the transmission seems like money well spent from what I've read.

Thanks again,
Luke

 

[jeepkj02]

I use a bottle pump, no spills to worry about!! I got one for gear oil and one for ATF.

 

[GSXRGUY]

To drain, first remove the fill plug (that way you're positive you can get new fluid back in there...nothing like removing the old fluid only to find out the fill plug is stuck on).

Really....I guess I should have read this first. It just took me 4 hrs to remove the fill plug.

It cost me 2 easy outs....SNAP!, 1 Bottle of Propane to heat the piss out of it, 6 Drill bits...SNAPPED and then shoved a metal file in the hole pounded on it until it was stuck then a pair of vice-grips and twisted it until I almost blew a NUT!! and it finally broke loose.

 

[2003KJ]

Really....I guess I should have read this first. It just took me 4 hrs to remove the fill plug.

It cost me 2 easy outs....SNAP!, 1 Bottle of Propane to heat the piss out of it, 6 Drill bits...SNAPPED and then shoved a metal file in the hole pounded on it until it was stuck then a pair of vice-grips and twisted it until I almost blew a NUT!! and it finally broke loose.

Yup....I almost learned my lesson one time changing oil. I normally would take the drain plug off, and while I was letting the oil drain out I would go ahead and change the filter and then take the oil cap off. One day, I had all the oil out, a brand new filter on, and went to take the cap off...and it wouldn't come off! Ended up getting creative with a hammer and a flat head screw driver to pry it out. From that day forward, the first thing I do when changing any type of fluid is make sure I am 100% sure I have a way to get the new fluid back in before I drain the old out.

 

[GSXRGUY]

Yup....I almost learned my lesson one time changing oil. I normally would take the drain plug off, and while I was letting the oil drain out I would go ahead and change the filter and then take the oil cap off. One day, I had all the oil out, a brand new filter on, and went to take the cap off...and it wouldn't come off! Ended up getting creative with a hammer and a flat head screw driver to pry it out. From that day forward, the first thing I do when changing any type of fluid is make sure I am 100% sure I have a way to get the new fluid back in before I drain the old out.

I have learned my lesson..Always have a way to get in, before trying to get it out.

 

[Powerslave]

Sorry to resurrect a thread, but, you HAVE to use Trans Fluid in the T-Case? Gear oil, like 75/95 (Royal Purple Synthetic) would not work?

 

[tjkj2002]

Sorry to resurrect a thread, but, you HAVE to use Trans Fluid in the T-Case? Gear oil, like 75/95 (Royal Purple Synthetic) would not work?

No gear oil will not work in our t-cases.Our t-cases are designed to run on ATF,gear oil is thicker and the oil pump for the cooler will not pump the thicker gear oil thus burning up the t-case.And yes our t-cases have internal coolers.