5speed4door

Hey guys, I have a shift issue with my 1996 Jeep Grand Cherokee 4.0 auto 4x4. The Jeep is completely stock with 176,000 mileage. It was shifting fine up until about a month ago and then this issue started after the Jeep sat for a few weeks. Now, it shifts fine under normal acceleration, but under heavier acceleration “putting the pedal about 1/2 to the floor or more” it just won’t shift from 2-3 and 3-4. If I let off the gas, it will shift. No issue with my 1-2 shift and all my downshifts seem fine. I’m not sure if it’s related, but I do have a low idle and it definitely lacks power. Feels like its missing about 45hp compared to all my other 4.0L ZJ's and XJ's I've had throughout the years. It has randomly stalled on my about 3 times in the 500 miles I put on it. However, it had that issue since I got the Jeep a few months ago. Also, I’m not sure if this could be related, but the transfer case has also given me some linkage issues. Hard to get back into 2wd the last couple snow storms. It is in 2wd now. I finally have the time to put into it, so I wanna get her in tip top shape. Step number one is figuring out this shift issue. I've read a bunch of threads to get an idea of what it could be, but I haven't found anybody with the same issue. Based off what I have read so far, I'm thinking it might be a bad sensor, ground, or TCM. I'm sure somebody here has a better idea of what it could be. I appreciate any help I can get.

- My trans fluid and fluid level looks fine.

- No check engine lights or anything. With the key on/off 3 times, I got code 12 which means “the battery was disconnected within the past 50 key on cycles” which is was. I disconnected the battery again yesterday for the hell of it, just to see if anything would change, but the shift issue is still there. My multimeter says my battery voltage is 12.3v not running and 13.7V running. Its about 1 year old.

TPS voltage was .78v at idle and 3.94v wide open when the Jeep was cool. Voltage climbed and dropped as it should when I opened and closed the throttle. I'm gonna check again when it's warm and tap on it while testing it.

All vacuum lines under the hood look fine.

I crawled under the Jeep and checked all wires going to the sensors on the trans and everything looks fine.

I have not tested anything else yet. I'm gonna put it on my buddies lift this week after some more reading up. I wanna make sure I have a detailed list of things to check and how to test them.