Strange Transmission Problems

[TrvlAce]

I have had my 1996 Pathfinder (2wd) in the transmission shop several times for shifting problems. They tell me there are no codes showing up and I had them flush the transmission. No relief. The problem is it won't stay in overdrive all the time, and sometimes shifts to 2nd gear sending the RPM to about 4000 while doing about 70MPH. YIKES! I notice this problem more at night and when it is cooler outside. I take it to the shop and the transmission acts just fine. It only does this when they are not open or I am 100 miles away from them. They tell me to bring it by when it does it...which is never when they are open. Any ideas?

[SnowSurfLax]

*cue Kouki and the transmission jokes*

I'd search around for transmission issues. I think you're year had problems with the stock cooler getting clogged and causing all sorts of problems. Only fix is an aftermarket transmission cooler and you'll probably also need a rebuild.

For now, flush by the manual's instructions (Haynes, FSM, etc) and see if that helps. Try running synthetic fluid and see ift hat help for the mean time.

[TrvlAce]

Normally, I'd agree with you. But if it were a clog, then it would do it if it was 100 degrees, or if it was 20 below 0 degrees. This event only occurs when it is cool outside. If the weather is nice, it does not occur. I had the transmission flushed already and no help at all. I have to wonder if a Mass Air Flow sensor would cause this? It shifts fine, just at the wrong time (early), like if you hit a slight rise, it shifts down, once you top the rise it shifts back where it should be. But it only does this when the air temp is cool, if it is hot then it won't do it. I also notice it after a rain sometimes, since the air got cooler than it was before when it worked fine.

[SnowSurfLax]

I would try searching for transmission issues for your year pathy. I don't think it'd be engine related. You might have a TCU going out on you?

The transmissions are computer controlled and respond to engine load. So if there's no change in engine load, you shouldn't have the transmission react unless there is a problem with it.

[nissandoms47]

Could be a bad tpms. TCU or ECU. try fiddling with the TPMS. If it thinks you're trying to accelerate it'll downshift when you're really not really accelerating. My 96 had TCU problems. Wouldnt shift right etc.. I replaced the TCU and ECU and TPMS and all that.

[TrvlAce]

Sorry for my ignorance but what is a TCU, ECU, and TPMS?

Thanks for the ideas guys.

[moparvwfreak]

TCU and ECU are transmission conrtol unit and engine control unit. basically the brains for the engine adn transmission. TPMS might be tire pressure monitoring system??? i have no idea,

Sorry for my ignorance but what is a TCU, ECU, and TPMS?

Thanks for the ideas guys.