So i have previously posted a thread on my issue, but it was prior to me really diagnosing/understanding the issue and was filled with a poor/misleading description of the problem, figured i would try again.

2008 JKU auto w/ 3.73 gears- 3.5" lift and 315/70R17 duratracs

Noticed recently that the jeep is prematurely upshifting, causing it to lug at low RPM's, lose power, and start hesitating. With my mini van engine, stock gears, and "35s", i am used to the jeep chasing gears a bit on the highway and not having alot of power behind the pedal. But it seems to have gotten worse and the hesitation is new. For example, I will be driving down the road in say 2nd gear at maybe 25% throttle and it will upshift to third, dropping the RPMs really low (sub 1500) and i will lose power. If i ease into the throttle, it doesnt go anywhere and starts stumbling/hesitating. I have to lay into the pedal to get it to downshift to get out of the stumble, rpms spike, and away i go.

Any ideas? My wires/plugs are maybe a year old. they were just "OEM replacements" maybe bosche or champs, cant remember. I run 93 octane almost all the time except for when gas$ is high and i go mid grade (running superchip tow tune). I am considering unplugging my battery for a few hours to clear my PCM in hopes it will reset my shift points...not sure if it really works that way or not (does it?)

Havent replaced any sensors since i bough the jeep, has 86k miles on it. no codes or CEL.

Oh ya, engine is a bit noisy but smooth idle and acceleration except when in low power band

Any guidance or past experience is much appreciated! Thank you fellow jeepers!

 

When was the transmission serviced last

 

Dropped pan and replaced filter and fluid maybe 15k miles ago. Fluid looks good. Was just below the lower hot notch when checked on a slight incline. Shifts smooth

 

Been pointed to everything from plugs to fuel pump, bad gas, random sensor and valves, injectors...not even sure where to start.

Ran some seafoam through the vacuum line and some in the gas tank. No difference (yet, still some in gas)

 

In order to be driving along in second, the lever would have to be in second.


See what it does with the O/D off.

 

Not sure what you mean by lever. Do you mean shifter? It's an automatic so I drive in D.
Still happens even with overdrive off. My overdrive is working fine though, I turn it off occasionally on the interstate when I see its chasing gears. Don't think it's an OD issue. Transmission shifts smoothly through all gears.

It's just when it up shifts at light throttle it bogs down in low rpm and hesitates and loses power until I hit the gas to downshift and get out of it.

By hesitate I mean it kind of studders, or kicks. Like it's just struggling to get going. The tone of the engine drops real low and kind of hiccups almost.

 

I was puzzled by your statement about driving around in second.
Since you are in D, and it still does it with O/D off, what you are seeing is the torque converter locking up in third. That can feel like a shift to a higher gear.
Have you programmed for the bigger tires? Have you considered re-gearing for the bigger tires?

 

Interesting , I hadn't thought of that. I figured it was just up shifting. Yes I have changed my tire size through my superchips. It was a while ago,I could remeasure and recalibrate.

It's never bothered me enough to want to regear. I purposely went with the duratracs because they run really light compared ti most "35s". Has just become noticeable in the past week. The hesitation is new.

It doesn't shudder like I'm driving on rumble strips like a torque converter usually would. More of a stall or kick. Hard to explain I guess

 

It seems like you have two choices, then.
Go back to stock tires, or re-gear to get the engine/transmission back into the correct power band.

What diameter stock tires did it have, and what diameter tires are on it now?

 

I've had my duratracs on for over a year with no issue and have always been very satisfied with the drivability. Just seems to have suddenly become more noticeable and the hesitation is new as well. Tires measure about 33.75" in diameter