Foaming transmission fluid and dipstick question
 

2002 WJ 4.0 / 42RE / 242

My son overfilled the trans, and it was driven like that for a week or two. Yesterday we disconnected the return line and dumped out the excess (about a quart). Since then it's been driven twice, a 10 mile one way, with a stop at the end. So, 4x 10 mile trips. The trans fluid is still foamy, as seen in the picture below (ignore the level; this was taken with the car on a significant slope). I'm wondering if I need to do a complete fluid exchange, or will this settle out on its own?

Second question. When I replace the dipstick it comes to a natural stopping point. It has a springy feel to it, but if I stop there, it's consistent. I can push past that about 3/8 of an inch before it solidly bottoms out. If I release it, it pops back to the first springy stop. Is this normal, and at which position should I take the measurement?


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Great foaming trans fluid, Batman!

I don't know about the bubbles/foamy fluid, but my dipstick is the same. I took cold and hot measurments by pushing it all the way down, and then pulling it out to read. That was awhile ago, and it seems to have been correct for in my case.

Sounds reasonable. I've done more driving, and I'll check in the morning (it's dark now). If it's still foamy, I'll do the fluid replacement.

ATF+4 I hope.

Ruh-Roh.

I think I might know somebody who is new to the Grands who just made a very stupid assumption. :blink:

So, how much fluid for a complete change out?

Probably 12+ qts to do a full flush..

Its going to need 12+ qts to do a full change-out of the transmission/tc fluid to do it right.. On my RWD WJ thats what it took to passive flush mine clean.

Disconnect the trans fluid return line at the radiator. Put that line into a jug (I hung the jug off the front axle.. I also poored three qts of the new atf into the jug prior to starting, and made a mark on it at that level on a clear one gallon water jug). Pull the trans dipstick. Put a chock under the wheel(s) & engage the parking brake. Start the Jeep. Put it in neutral (fluid starts pumping out now into the jug when its in neutral). Get out and go look at it while its filling up the jug. Once it gets close to or at the three qt mark on the jug, jump back in the Jeep and put it into park. Take three qts of the new atf, and poor them into the dipstick. Remove/empty the jug of old fluid. Put the return line back into the jug again. Get back in the Jeep and put it in neutral. Get out and watch it fill up the jug. Once close to or at about the three qt mark on the jug, jump back in the Jeep and put it into park. Put three more qts of new atf into the dipstick, empty jug of old atf, put line back into jug again... Repeat that procedure until you have replaced at least 12 qts of the new atf, and it should be all replaced at that point.

Mine had nice and clean atf coming out of the return line once I reached the 12qt point of the procedure. It was with a RWD only (not 4×4) model WJ. So, I think for the transfer case you may need a little more than 12qts? Maybe closer to 15-16 qts in all...

The pan holds close to 4qts. Doing it this way with pumping out only 3qts at a time, and then replacing that amount is a safe way to do it.

Once its done it should be very close. Check the measurment levels cold & then hot. Add some if its needed. I heard to move the shifter lever through all of the gears first a few times before driving is a good thing, but I think just common sense and taking it easy you know. Does it feel right, shift, and sound okay? If the pumps running dry, you'll hear it and be able to tell...

Transfer case shares the same fluid? I don't think so. Can anyone who is sure about that weigh in?

Nice trick with the 3 quart mark on the jug. I have helpers, so I'll probably do it all at once. One guy pouring, one guy watching the output, and one manning the ignition.

I had to go to 3 different stores to get enough ATF+4! :blink: I picked up 13 quarts, to be safe. That stuff ain't cheap, so I'm going the WalMart brand route for this flush.

I am toying with the idea of doing it all over in a couple of weeks, just to be sure..... Thoughts on that?

They do... NOT, do they? Who in the world did you hear that from! Woops sorry I was saying one thing and thinking another. I meant to say TORQUE CONVERTER. I'm not even sure where all I was going with that anymore now either? I think its 12 qts for both 4×4 and 2wd, right?

Mine was clean atf coming out after the 12th qt... I'll just leave it at that if it helps 🙂

I don't know about how detrimental it is having the wrong type, or having which of the wrong types of atf in the transmission is for it? Except to say, I know that sometimes, depending on those factors, it is really bad! Also, not sure of which ones, outside of +4 being backwards compatible with +3, don't mix well either? Because of those reasons, and transmissions being expensive to repair and replace, I would probably want to flush it all out really well. Maybe drive around for 10 to 20 miles, and then do it again if it were me.

Yes, the t/case takes the same fluid as the transmission (ATF+4), UNLESS you have the NP249 which takes a special fluid available only from a dealer. HOWEVER, the newer constant 4wd t/cases may be different. For instance, the ZJs and WJs with the 242 take ATF+4, the XJs with the 231 and 242 take DexIII/Mercon, the ZJs with the 249 take Mopar Transfer Case Lubricant. That's all I've had experience with.

You will notice the 242 in XJs and ZJ/WJs take different fluids? That's only to make it easier for the owner to service them because they are simple gearcases and only use the fluid as a lubricant, not in a hydraulic pump to shift clutches. Yes, they have pumps in them, but only to circulate the lubricant. The early New Process t/cases used the GM trucks just specified Dextron.

So, to be clear then... (not including the NP249)

The transfer case and the transmission both get filled with/use the same type of atf fluids.

However, when servicing.. in order to change out these fluids from both the transmission and the transfer case, they are seperate procedures right? The transmission fluid (which is in one interconnected system to include the fluid being utilized by the torque converter) can all be flushed out and replaced through the method mentioned above with the transmission return line being disconnected, putting in neutral, and filling up by pouring new atf into the transmission dipstick tube. This is the correct, or best way to flush it all out since only dropping the transmission pan to drain the fluid does not remove the atf that is still going to be in the torque converter right?

Now, for the transfer case.. The procedure, or method mentioned above, does nothing to flush, drain, or remove transfer case fluid (which just happens to be the same atf fluid that goes in the transmission as well).. because that is an entirely seperate procedure, method, or process alltogether. There is a bolt (or maybe its a drain plug of sorts?) to remove from the lower portion of the transfer case. Probably very similar to doing an oil change right? Remove that and the transfer case fluid drains out of it. Put the bolt (or maybe its a drain plug of sorts?) back in the spot where you removed it from.. Then, to refill the transfer case back up with fluid (the same atf that is used also in the transmission.. which the transmission shares passages to and fluid with the torque converter), there is a bolt or plug of sorts in the upper higher portion of the transfer case to pour the fluid into, until it reaches the level of the opening (similar I believe to how you would refill the differentials back up with differantial fluid (which the fluid the differentils use will be an entirely different kind of fluid from that which is used by the transmission and the transfer case.. and in no way does the differentials interconnect, or share passageways to either the transmission or to the transfer case)....

Does that all sound right?

Correct! However I suggest you pull the fill plug on the T/case BEFORE you drain it! Making sure you can get it out so you can fill it. They are 1/2" pipe plugs with a 10mm hex socket in them. They are NOT 3/8" and sometimes they will strip out the hex if you use a 3/8 Allen wrench. Then you're screwed because the plugs expand and are a real bear to remove.Trust me, I've been there!

The transmission and t/case are completely separate from each other. There is a drain slot in the flange where they mount together for seal leakage to drain from. Both the transmission and the t/case have seals on the input/output bearings so they stay separate. Any leakage from those seals will drain out the bottom and unless it's a large leak, it's difficult to figure out which is leaking.

T-case is not part of this issue, gentlemen. It has not been touched. It only came in because Noah had a brain fart. It happens. :)

Good stuff! I believe I've learned something today!

I have a question now though. Say I forget to remove the fill plug first, before draining the transfer case of fluid. I can't get the fill plug out no matter what I try... Do I have to flip my Jeep upside down onto its roof to fill the transfer case back up from the drain plug hole now? And how do I know how much fluid to put back in it when I have to fill it up from upside down like that?