I have a 07 caravan with the 3.8 v6 and what I assume is an a604 trans. I have been having problems with a shuttering/jerking at around 30-45 mph, when also at low rpms (less than 1700). If I keep rpms over that, it's fine. At first I thought it was the overdrive, so I started driving in 3rd until I was past 50 mph, and shifted into OD. This works fine for highway driving. However, in city driving, it does it anyway. It's fine when in 2nd, but after it shifts up to 3rd, it jerks any time I put it under any kind of load (again, only at low rpms) Even though the fluid looks okay on the stick (color and level), I think I'm gonna try to drop the pan to change the filter and fluid (not full flush though). The van was my father's (who passed away last year), and I have no idea when it was last done. Generally, he was good about maintaining his vehicles, so I would imagine it was kept up with...but idk. Also, the van sat for about a year. I've put about 500 miles on it over the past few weeks, and other than this, it's fine. Any suggestions? I'm just using it temporarily to get to work, so I'm not going to put much money into it; say $150-200 max, as it's not worth much. Also, if this is just an annoyance, I can deal with it for a few months. However, if it's on it's last legs, that's another story. Thanks for any help.

 

I ended up changing the trans fluid and filter this afternoon (as well as engine oil and filter while I was at it). There was not any noticeable shavings around the magnet, just what the YouTube mechanics say is a "normal" amount of black sludge in the bottom of the pan. I also added a bottle of Lucas stop-slip, as I heard it can be helpful. So we'll see. During my first drive back home (less than 5 miles), I still noticed the issue, but I'll reserve final judgement, as I was told to drive 200-300 miles before I decide whether or not it helped or not.

 

So, it's now been a little over 500 miles since the fluid change, and the problem is still present. Though it's unrelated to the trans, I have even tried the lacquer thinner "trick" I saw (1 gal of it in 10 gal of gas) in hopes that the fuel system was a little gummed up from the old gas sitting in the throttle body and stuff for so long, and still nothing.
My brother recently used his OBD2 scanner, and it showed the following engine codes:
po456 small evap system leak
po404 Exhaust gas recirculation control circuit
po440 EVAP purge system fault
There wasn't anything for the trans though, so that's odd. He cleared all the old codes, but I'm going to hook it up again soon, so see what came back up. The gas cap message was popping up for a few days, but has now quit. From what I understand, small evap leaks wouldn't negatively affect the motor's performance, but correct me if I'm wrong. Perhaps a problem the EGR valve could be the problem?

 

Look into the po404 problem. A bad EGR valve can cause the engine to stutter.

 

So I ended up buying a can of carbon cleaner (CRC valve and turbo) and cleaned the egr valve and tube. There was a disturbing amount of carbon buildup on the intake fitting. Enough that I really want to take the intake off and thoroughly clean it as well. Unfortunately, one of the bolts for the tube broke off. Once I reinstalled it, it doesn't seem to be leaking, so I'm gonna leave it be for now. For that reason, I did not remove the valve from the engine, but squirted a little into the orifice. I also took the air boot off and cleaned the throttle body (also quite dirty). The problem hasn't completely went away, but is noticeably better, so that I can drive around town at slow speed without much trouble, so that's cool.

 

Have a shop run a scan on it, we had the same problem and it wasn’t showing a code on my OBD2 scanner, but their pro scanner showed a blocked catalytic converter that was affecting a chain reaction with sensors and on board computer was adjusting as best as could and causing the shudder in tranny. new catalytic converter and problem went away