Transmission problems in 08 avenger... HELP!

My wife has a 08 avenger with the 2.4. We bought it in late 07, with 16k. I'm pretty sure it was a test mule car. It now has 170k and has been a GREAT car. Other then change the oil brakes and plugs, I've never done anything to it. Which also means I've never serviced the tranny. Earlier this week she said it shifted really hard into 2nd but never did it again. I have a buddy who is a really good mechanic and he plugged it into his scanner and it didn't have any tranny codes. Then this morning she sends me a pic of the gauge cluster and it's spinning 4500 at 75. Crap! For some reason it's not shifting.

Any idea on common problems with these transmissions? I'm thinking I should service it and put a new solenoid pack on it. But I changed jobs this year to something that I am much happier doing but took a pay cut so our budget is tight. I hate just throwing parts at things. My buddy said he doesn't think it's in the solinoid pack since it didn't have any codes, but we haven't checked them since it decided to not shift this morning. I was thinking maybe the solenoid pack just needed cleaned, but they are only $100 so I figure I might as just well change it so I'm not back in the tranny again and wasting fluid if cleaning doesn't fix it.

Any help is greatly appreciated. We are down to 2 cars at the moment so I really need to get this fixed.

Its going into second gear limp-in. Trans is detecting an input/output sync error. It should have a code now so it might be worthwhile to have it read again.

Did you check fluid level/ condition?

And the only way you can buy an ex-"M plate" is through the Marshalling Center in Auburn Hills, MI btw.

Like was said. Only way to know is pull the codes. Speed sensors are pretty common to go bad.

Just change the transmission.

Owner manual says to change fluid every 60k, it is well pass that, no point changing anything on it, just drive it until it dies and put in a used/rebuild transmission there.

page 430
http://www.dodge.com/download/pdf/ma...venger-3rd.pdf

4 speed or 6 speed?

Early 2.4l only came with 40te.