I've had flickering headlights, sometimes accompanied by dash display dimming intermittently, going on for a couple of years now, but only once or twice a week, so no big deal.

But now I am seeing erratic speedometer, followed by trouble codes 700, 720 (and sometime 731/732) and usually the car going into limp mode. This also is intermittent and happens 3 or 4 times a week at any random time, not related to rough terrain or outside temperature. However, I've never seen the problem happen until the engine has warmed up.

After reading forum posts and watching this behavior over the past few months, got my charging system and ground connections checked at Firestone...no problem found there. So of course all they could suggest was to change the input and output speed sensors first, and $350 later no change. Unfortunately most people posting on this forum with the same symptoms are not reporting back what actually fixed the problem.

I don't want to spend a fortune on guesswork, so I'm hoping someone can suggest a good way to narrow this down, or better yet have enough experience to know the majority of the time they have seen the same problem the fix is: [fill in the blank]. The local dealer and my regular mechanic can't tell me what they will do next because the problem cannot be reproduced on demand, but when I hear something that makes sense then I can take these suggestions to my mechanic.

Possibilities I've read about so for would include the alternator diode, solonoid pack, PCM and TCM. Any advice would be greatly appreciated.

 

Any expert opinions out there?

 

Firestone referred me to a transmission shop after taking another look. The tranny guys say they connected some diagnostic equipment to help isolate the problem while driving, which points to wiring. Finally, someone who seems to understand and is able figure this out!

Unfortunately they also said there is metal in the pan. I've maintained this car according to Chrysler recommendations since the beginning, so I can only guess this is either normal at 100,000 mi, or that the occasional and barely noticeable downshifting over that last 500 miles have resulted in excessive wear. I have not driven over 40 mph since the first time I noticed the speedo symptoms. For an otherwise perfectly working transmission I would hate to think they would use scare tactics to convince customers to drop the transmission for a $600 inspection fee.

 

$2,500 is the total estimate. The diagnosis from the experts is the solonoid block and harness, but also recommended a re-build kit and valve body. (I never saw P1776 associated with a stuck solonoid). At least I can now take it back with no extra charges if the speedometer freaks out again.

Hmmm, shure hope my re-built transmission will least a year longer than their warranty. I'd love to keep the 300M now that I'm paying more for a repair than trade-in value.