My issue started as a shudder that would intermittently occur as the transmission was upshifting when accelerating at low speeds. Backing off the pedal and then getting back into it would give it a chance to "catch up" and fully engage the gear. I used Lube Gard Instant Shudder Fixx
(https://shop.advanceautoparts.com/p/...earchTerm=Fixx), which eliminated 80-90% of the shudder events. I let it go for about 3 months, and about 5 days ago, my wife was getting on the highway when the transmission "acted like it was in, like, neutral, and now it won't, like, go out of 3rd gear." I asked if there was any kind of noise (ie. clunk, pop, ect) that occurred when it went from drive, to "like, neutral", to 3rd gear, to which she replied 'NO'. After a little research, I have found out that the tranny is stuck in "limp mode" (in case you're not familiar, this is a fail safe mode that keeps the transmission in 3rd gear to prevent damaging the transmission but still allowing you to get home or to a service shop). At the time, my wife was working for Grub Hub and was in the process of taking the customer's food to them, so she dropped off the order before returning home. She was able to back out of the parking spot she was in to make her delivery, but since then, it will not go into reverse. It initially had a check engine light, code 0755 I believe. The description of the code was the output speed sensor was out of range from the input speed sensor. We did not experience any speedometer issues/twitches, so I opted to change the Solenoid pack and cleared the code. There was no change except there was no longer a check engine light or TCM code being thrown. I just got done changing the output speed sensor. No change, still no code. Tomorrow I will be changing the input speed sensor, but at this point, I don't expect this to solve the issue. Outside of possible internal tranny issues, or the TCM being bad, I think it's possible that the transmission is stuck in limp mode for some reason (I'm not certain how to get it out of limp mode, all I have found is just to shut the car off, wait 10 secs - 2-3 hours, then start the engine and continue driving (which has not worked). Or possibly the TCM itself. My next idea involves pulling the tranny, which I would like to avoid if possible. I've done a ton of work to this vehicle, but I don't think much, if any, would relate to this, except for changing the transmission oil pan gasket, fluid, and filter about 5000 miles ago. But just in case something does relate, here is what I've done to the Pacifica within the last 8 months/35000 miles
20000 miles ago (approx) - AC Compressor
15000 miles ago (approx) - Alternator, Front and Rear Rotors and Pads, Water Pump
17500 miles ago (approx) - PS Pump, Battery
15000 miles ago (approx) - Radiator (used), Blower Motor, Blower Motor Resistor, Coil Pack
10000 miles ago (approx) - Front Quick Struts, Control Arms, Bushings, Ball Joints, Plugs, Wires, Air Filter
7500 miles ago (approx) - Rack & Pinion, Inner & Outer Tie Rods, Stabilizer Bar links & bushings, T-stat & Housing
5000 miles ago (approx) - Engine oil and Transmission oil pan gaskets & Filters, Radiator (new)
500 miles ago (approx) - Tires (originally 235/65/17 -> 275/70/17)

I'm sure I'm forgetting something but you get the picture. I welcome all ideas and/or experiences. Thanks to all who respond.

 

Oh, now I know what I forgot. Motor mounts approximately 15000 miles ago.

 

My 06 Pacifica had the limp home problem, I think it was caused by the "right" combination of error codes. Anyway, I undid the negative battery cable for a while. This reset all of the codes and all was fine, One other time it did it again, same reset and that time it seemed to fix it for good.

 

My 07 Pacifica once went into trans limp mode when I jumped the battery. I assume the low voltage before the jump got it into the state. New battery and shorting the battery leads together for 30 sec restored the trans to normal mode for the next 50K.