[Sclay115]

96 4.0, so a 42RE, now, I have read all the information I could on this thing, and I still cannot get this slushbox to quit leaking.

Let me start from the beginning. Purchased the Jeep, yep, the trans was leaking, from what looked like the pan, and the front cooler lines. I noticed the RTV on the pan and said to myself, "I'm pretty sure the 42RE uses a pan gasket, a plastic one I believe." Sure enough it does.

So instead of just fixing the lines, and resealing the pan. I bought myself a big old trans fluid cooler, and in the course of a weekend, did a drain and fill, and added the cooler, removing the front quick disconnects and subsequently, the check valve, in the process. Bolts on pan torqued to 13-15ft lbs after replacing the lovely RTV with an OEM pan gasket.

Get her filled up, get the fluid level correct, drive around a bit, put it in N and sit under the truck looking for any leaking lines from the cooler install, taking only a momentary glance at the pan to make sure it hadn't flown off, it was still there, thank goodness.

Drive it home, park it in front of the condo, lay my weary head to rest assuming everything was awesome and that the ZJ was going to be extremely happy with it's new found leak free system.

Come out in the morning to find a nice puddle of ATF 4 on the ground under the pan. Well, obviously there is something wrong here. Yesterday, put it up on the lift, pull the pan, recover the fluid, and begin to take a real good look at the mating surfaces. The pan seemed a little tweaked, but not a bunch, straightened it out anyways using a ball peen and an anvil. Let the trans drain for a very, very long time, hoping to not run into any ATF finding it's way onto the gasket surface, ruining the seal.

I finally declare it drained enough, put the pan back up there and torque all the bolts back down in an X pattern to the 13 ft lbs. I also reseal what I believe is the neutral safety switch(drivers side of trans, 3 pins), just in case. Fill it with fluid, and with its still on the lift, started it up, ran it through the gears for a bit, popped it in N and picked it up. This time, I stood under the truck, with a flashlight, trying to find a leak, anything that would indicate to me where it was coming from. Nothing. Dry.

I was hoping the small bit of deformation in the pan caused it not to seal, and now I was good to go. But, as you can imagine from the rest of the post, I come out this morning to a very good sized puddle of ATF gathering under the Jeep, with a steady drip drip from the front of the pan.

Seriously, what gives? It could not have been done any more properly, or any cleaner, than how I did the job yesterday. I think there is either voodoo at work, or my Jeep just hates ATF 4.

Thing I want to add, it does not appear to leak while underway, how do I know this? Well, at the rate it is leaking, the entire undercarraige from the trans back would be covered with ATF, and it's not, it's bone dry. So that's a plus, sort of, as it just makes it harder to diagnose.

Thoughts lead me to the problem having something to do with the removal of the check valve. Now, I don't know the physical(height) level of the transmission fluid when the vehicle is off on a 42RE, but could the check valve keep unwanted fluid from draining back into the pan, keeping it below the gasket level? Would removing the check valve cause the level to rise at rest, bringing the level over the gasket surface, and possibly causing a leak? But while underway, there is enough fluid being circulated through the system to cause this issue to disappear?

My last resort is a cast aluminum pan, with a very thick machined mating surface, one that just simply can't possibly leak in regards to the pan. But, it's 130$ bones I don't want to have to spend if it's not going to fix my issue. It's not costing me anything but a half quart of ATF(typical loss in recovering fluid) to try and diagnose this, but I HATE leaking vehicles, and it's really just a time waster to keep having to fuss with it.

The transmission from the pan surface up looks dry, for those who might think it's a selector shaft seal. It really doesn't look like it could be from anywhere north of the pan, then again, I could be wrong, as I cannot seem to locate the leak at all...

Any tips, or thoughts?

Steve

[Sclay115]

No input from anyone?

Steve

[Foundrydude]

You need to clean it up thoroughly to identify the source of the leak, pan versus lines versus other tranny seals like the shifter linkage. If it's the pan I'd say it's time for a new steel pan. Probably don't need to go all the way to an aluminum pan.

[TallyZJ]

There are many places a transmission can leak. You only addressed two of them. It can leak from the front pump seal and run down to the pan and look like a pan leak. It can leak between the transmission and the t-case at the output shaft seal. Can leak from any of the shifter shaft seals or speed sensor seals.

Any of these leaks will ususlly accumulate on the pan edge and drip from the pan.

[Sclay115]

Tally, I understand what you are saying, but typically, a leaky seal in any of those positions will cause it to leak while underway, giving the vehicle a nice coating of atf underneath. I have none of that, which leads me to believe it is an "at rest" leak, and coming from the pan. I did do a thorough cleaning this last time it was on the lift, used a good amount of the shops brake clean, and a bunch of shop rags to get it as clean as I could, above and below the pan/gasket line. There also isn't any fluid on any other part of the case, and from what I have learned in the past, is that typically, leaking fluid doesn't travel upwards. So if you can find where the leak "stops" above a certain point, it is more than usually below that line.

It might simply be that the pan is tweaked enough to not be fixable, which is really reasonable, since it was a recent purchase, and that most previous owners like to botch things up. I'm going to re-check the pan bolts, make sure they are all at spec, in a few days, after the trans has time to heat cycle a few times.

I'm going to let it chill for a bit, it's aggravating enough to not want to deal with it every weekend. And since it is only leaking when it is parked, it really doesn't end up losing too much fluid over, say, a week's time.

Steve

[TallyZJ]

Originally Posted by Sclay115

Tally, I understand what you are saying, but typically, a leaky seal in any of those positions will cause it to leak while underway, giving the vehicle a nice coating of atf underneath. I have none of that, which leads me to believe it is an "at rest" leak, and coming from the pan. I did do a thorough cleaning this last time it was on the lift, used a good amount of the shops brake clean, and a bunch of shop rags to get it as clean as I could, above and below the pan/gasket line. There also isn't any fluid on any other part of the case, and from what I have learned in the past, is that typically, leaking fluid doesn't travel upwards. So if you can find where the leak "stops" above a certain point, it is more than usually below that line.

It might simply be that the pan is tweaked enough to not be fixable, which is really reasonable, since it was a recent purchase, and that most previous owners like to botch things up. I'm going to re-check the pan bolts, make sure they are all at spec, in a few days, after the trans has time to heat cycle a few times.

I'm going to let it chill for a bit, it's aggravating enough to not want to deal with it every weekend. And since it is only leaking when it is parked, it really doesn't end up losing too much fluid over, say, a week's time.

Steve

True. However, the pan gasket is designed to take care of most minor tweaks to the pan. It would have to be awfully bent and twisted not to seal?

What about a small crack at one of the pan bolt threads?

I dunno, perplexing leak.

[Candymancan]

Get a clean white rag... after you clean the transmission up top and bottom, stuff the rag between the sensor thats on the driver side above the pan.. Let it sit overnight and check it in the morning.. if there is no atf it isnt leaking from that sensor. Do the same for other position and parts until you get a source..

[Sclay115]

Originally Posted by Candymancan

Get a clean white rag... after you clean the transmission up top and bottom, stuff the rag between the sensor thats on the driver side above the pan.. Let it sit overnight and check it in the morning.. if there is no atf it isnt leaking from that sensor. Do the same for other position and parts until you get a source..

That's a great idea. I resealed that sensor when I did the pan the last time, but I think I'll give this tip a shot.

But yea, it is a very odd leak, with no apparent faults as to where it could be coming from. I did not know that about the gasket, I was under the impression that both surfaces had to be basically completely flat for the gasket to function correctly. I guess the ridiculous amount of time I took making sure the pan flange was flat was a little excessive!

Thanks for all the suggestions so far folks. Great to have a resource like this available.

Steve

[Sclay115]

Wanted to ask here, what is the potential of fluid leaking through the threads on the pan bolts? Took a trip out to Colorado, and had the ZJ parked in the airport garage. Came out, after four days out there, to about a quart of ATF accumulating underneath the Jeep. I am positive the EPA loves me. I do however need to get this pig fixed.

I wasn't going to crawl underneath it last night(late flight), but drive the two hours home, park it, come out this morning for work, and there is barely a half dollar sized drop of ATF on the asphalt. Elapsed time was about 5 hours(was a very late night/early morning), so it was a short time frame, but I can't seem to understand why it would leak only while static.

Still haven't done the rag yet, but will try that out this week.

Steve

[TallyZJ]

Originally Posted by Sclay115

Wanted to ask here, what is the potential of fluid leaking through the threads on the pan bolts? Took a trip out to Colorado, and had the ZJ parked in the airport garage. Came out, after four days out there, to about a quart of ATF accumulating underneath the Jeep. I am positive the EPA loves me. I do however need to get this pig fixed.

I wasn't going to crawl underneath it last night(late flight), but drive the two hours home, park it, come out this morning for work, and there is barely a half dollar sized drop of ATF on the asphalt. Elapsed time was about 5 hours(was a very late night/early morning), so it was a short time frame, but I can't seem to understand why it would leak only while static.

Still haven't done the rag yet, but will try that out this week.

Steve

If a transmission leaks while parked it should be easily identifiable as to where the leak comes from before it is driven and the fluid spreads. Clean it off as described earlier and just let it sit for a few hours and then go back and look for the leak.

Bolts do not usually leak as they are not directly drilled into the fluid reservoir or pan area. If a bolt leaks through the threads there would be a small crack through the transmission pan mount surface that allows fluid to escape through the crack and out the threaded hole.

[Sclay115]

Okay, cleaned it up after work today, let her sit and took a look just a few minutes ago.

Looks like the leak is coming from the driver's rear area above the pan(I think?). Conveniently located where all the sensors/switches are located back there. Now, it's hard to see up there with the driveshaft and tunnel in the way, but it does sort of look like the leak might be up above the rim of the pan. There is some fluid up there, but not a whole bunch, however, it is there. So I am thinking, with all the work I have put into sealing the pan, the culprit has to lie up there.

Okay, so here is where I am at. Now I am wondering, what should I be looking at for seals and such? Looks like the neutral switch, and another electrical connection up there. And I believe there is the shaft seal up there too right?

Alright, so you folks have been a huge help already, but I need some more ideas, I am trying to imagine in my head where the static fluid level would be so I can diag further. Any help on that? And what is up there that I can replace? Besides have a physically leaking switch or connector.

Steve

[Candymancan]

Is this the sensor your talking about on the side ? Try sticking a clean rag between the sensor and see if its leaking from it or not. Or take the plug off like in my pic and see its coverd in atf (notice the red droplet on the plug in my pic) My bet is your NSS is leaking

[Foundrydude]

Isn't there a push-lock trans line right up there? They are famous for needing the seals replaced and will drain the line when you park.

Most of the other potential leakers in that area are above the fluid level, so the only amount they will leak is what's sliding down the case after shutoff. You're talking a few drips. Whereas the line holds a fair amount of fluid and will cause small puddles like a dripping trans pan.

The rag idea is a great one, but generally if you clean the area well the trail will be visible with a light or mirror.

good luck

[Sclay115]

My first thought was the line. As I do know most of those connection setups are very common to leak after some time. However, the lines are dry, some small fluid, but no drips, and nothing that could cause this much of a leak. At least, I don't think. And the lines angle a bit towards the ground as they come out of the connection, so I would hope I could see it accumulate on the lowest point of the line before it makes it way to the ground. But in this case, it is definitely leaking from somewhere that is allowing it to drip from the pan itself, so I am thinking it has to be somewhere on the case.

Now, Foundry, you mentioned the NSS switch before too, I still have yet to do the rag trick, however, is it possible for the switch to just be flat out leaking? And have nothing to do with it leaking through the threads, but leaking through the switch itself? That seams like the most likely culprit, as it would be below the static fluid level(correct?), when the vehicle is parked. I resealed the threads before, but obviously, if the switch is just going to leak, well, it's just going to leak...

Steve

[Candymancan]

Yes, mine was leaking through the switch itself, hense why i said to unplug the switch and see if you get atf coming outa it