It's happened a couple times before at random, and I chalked it off as just one of those Jeep things. Until recently. I don't DD my WJ anymore, and I had it out yesterday for the first time in a couple of weeks. When I would hit bumps at a certain force, it seemed like it was being put into 1st gear while I was going 70. (speed makes no difference, but it did happen on the interstate 3 times in a 5 mile stretch).
At first I would've described it like someone hooked up a 100,000 lb trailer all at once, but I think describing it as a sudden 1st gear selection would be more accurate.
So after fixing the A/C (new condenser and accumulator-Pics in build thread), I've been driving it for the last couple of days. It seems to happen when the rear axle hits a bump. I noticed that it makes the same sound (bang!) it does when shifting in/out of gear with the drive train under stress/load off-road.
It seems like it's kicking in and out of overdrive, but really really hard.
I drove it to work today, and it started happening on my way home. I turned overdrive off to see if it made a difference, and it would turn OD back on itself, just after the "sudden loss of power" I've been feeling.
I am still having issues with the transmission. I've been driving it for the past week (probably horrible for it) to try to dig deeper.
While sitting still against a concrete wall, I can hear the shift solenoid operating like it's trying to change gears, although it doesn't need to while I'm sitting still. (you know, the classic Chrysler transmission shift noise). This morning at McD's, while my foot was on the brake, it changed gears and lurched forward. I've figured out that when I manually pull it into 1st, it seems like it's in first gear (power is normal-like it's always been), then the RPMs jump and the Jeep takes off like a bat out of hell.
My money's on the shift solenoid, but it's blowing my mind that I'm not getting a CEL (at LEAST a P0700) for it.
Update on the trans situation. I called a local trans shop. All the guys in my local Jeep Club recommended them. I called the shop, told him the trans model and the symptoms I was having. He said that he could look at it the 2nd or 3rd week of July, and mentioned that it was kind of common for the screw holding the flat, sump filter to come out when the trans isn't serviced on a regular schedule. He told me to pull the pan, replace the filters and fluid, and report any abnormalities back to him.
I ran out and picked up a filter kit this evening ($24.99 for the kit--both filters, pan gasket, and o-ring from autozone) and will be doing this tomorrow. I'm keeping my fingers crossed that what he mentioned is in fact the issue, and why it's not throwing any kind of code.
Changed the fluid and filters yesterday. Finally got to test it today after putting my new unit bearings on and going for a drive.
It still does it.
I had a wild hair that it might be something floating around in the rear end, so I pulled the cover off. I don't see any abnormalities, but I don't have the wheels off the ground yet to rotate the gears either. Tomorrow evening I'll do that.
Mine is having similar symptoms to yours. It bangs hard when trying to shift into Overdrive. It shifts fine if I have Overdrive turned off. It also did the "shift down to first gear for a half second" thing once while I was on the freeway. Not fun at 75mph... Fluid level is fine. I changed fluid and filter a few months back and it shifted great until a couple weeks ago. Mine did throw a P0700 code after the first harsh shift, but I was traveling and didn't have access to a scanner to get the specific trans. code. Good luck, Narn. I hope you figure your issue out. If I figure it out, I'll let you know.
2002 WJ Overland - 4.7HO - 231tc - 6" Clayton - 285/75-16 Cooper STT - ProComp 5129 wheels - Kevin's Offroad Belly Skid and Rock Sliders - JKS Track Bar and Disconnects - ProtoFab bumpers