2002 QX4 Transmission fluid atf exploding from dipstick tube

[TriniTT]

Hey all, I recently acquired a 2002 qx4 that had some issues I have been working on eliminating. As a preface, I have over a decade of extensive auto tech experience, I work for a company that does custom engine wiring harnesses so I am more than familiar with the FSM of this vehicle and how to troubleshoot technical issues in general.

I drove it recently and it seemed to be lacking in power and did not shift quite as smoothly as I would have expected. I checked the trans fluid and it was a bit low, so I added until I got a proper reading on the hot mark once it was warmed up, trans in park on a level surface. I drove it a couple of miles today and stopped to check the fluid again. To my dismay, at the first crack of the transmission dipstick tube seal on the dipstick, it exploded ATF with incredible force everywhere! I have searched high and low and cannot find anywhere that others have seen this issue. Any advice would be greatly appreciated.

I will note that I had this issue earlier, but was getting a code p0740, so I replaced the corresponding solenoid and also replaced the strainer and oring at the same time and hoped the solenoid might have been the culprit. The code is now gone, but I am still seeing the over-boiling or pressure issue from the dipstick tube. I have read other posts claim that there is a vent somewhere on the trans that should relieve any such pressure, but I cannot locate that vent anywhere and I do not see it on the FSM diagram. The car has issues not wanting to shift correctly, still has a lack of power under acceleration, and wants to stay in a specific gear even up to 5k rpms while cruising on the interstate with virtually no throttle. Eventually it will drop into a higher gear, but none of this behavior seems normal to me.

[4xq]

Take a look at this picture of a transmission for sale on ebay: http://www.ebay.com/itm/2002-NISSAN-PAT ... a0&vxp=mtr

Looks like the vent tube on the top driver side of the transmission, about even with the back of the pan. If you zoom on the pic, everything else is just wiring lying on top of the transmission.

I am not sure, but I think the vent may T into your transfer case vent. If the blockage is past that T, your transfer case may have been pumped full of ATF. Worth checking I think.

Good chance its a vent problem. If not, you'll be dropping the pan.

Post back and let us know what you find! I am curious to know if those vents do really tie together.

[TriniTT]

Ah nice and thank you, very helpful! I will take a look tomorrow and report back with my findings. I am a bit curious regarding your comment about the transfer case being pumped full of atf, is this something that can happen from a component failure? Or were you indicating if someone previously overfilled the transfer case? I'm not sure how that would be possible given the fill method, but I would definitely like to know if there is some component that could fail and cause the trans atf to flow into the transfer case. I have not had the opportunity to open one up yet to see how it works together, but my transfer case is leaking from the motor seal so I planned to tackle that this weekend and I'm curious if there is anything else I need to look into.

[4xq]

Well, I chased this a little further out of curiosity.The vent hose parts diagram is here: http://www.courtesyparts.com/pathfinder ... _4774.html

The fifth diagram down applies to 2002 4 wheel drive. This is a Pathfinder diagram, but your QX4 is the same. All metal tubes starting with part number 31098 are pieces of the transmission and transfer case vent lines. There is a vent line for each of them that apparently runs up the passenger side frame to a vent tube under the hood, likely near the passenger side firewall, part number 31082u.

If your vent is indeed blocked, it can be any where in the transmission vent line pictured. So that may be a little more work to chase down than I would have thought.

Let us know what you find out!