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Our 2002 Dodge Grand Caravan Sport vibrates & runs poorly between 40 & 50 mph but runs normally at speeds below or above this range. I thought at first it might be a tire or alignment problem but now I’m guessing maybe a transmission or motor mount problem. Let me know if you have had similar problems. Thanks.

Try moving the wheels front to back and see if it changes. If no change then it is not the wheel or tyre. You also may want to look carefully at the tread. If there is uneven wear, that could be both or ether the problem or the cause.

A vibration between 40 & 50 mph could certainly indicate a tire problem or a front-end problem, so Mr. Meehan’s suggestion is a good one. However, I am wondering about the “runs poorly” part of the situation.

“Running poorly” would seem to indicate something other than a tire or front-end problem, but an explanation of exactly how the vehicle is running poorly is in order here. Is there hesitation when you try to accelerate within that speed range? Does the vehicle “lack pep” within that speed range?

I am surmising that this is a driveability problem that lies in the engine, rather than the transmission. Between 40 & 50 mph, the transmission should be running constantly in 4th gear unless you attempt to accelerate sharply. Is this a problem regarding an inability to make the transmission “kick down” to 3rd gear when you want to accelerate? Is the transmission constantly “hunting” between 3rd & 4th gears?

If none of those scenarios applies, then I would suggest that you consider the maintenance that the engine has had. When were the spark plugs last replaced? How about the air filter, fuel filter, and pcv valve? If these items have not been replaced w/in the past 3 yrs/30k miles, then the problem could be related to those maintenance items. If you don’t know when those items were last replaced, then it is time for this to be done.

I am assuming that the Check Engine Light is not illuminated. But, if it is, then that would be the first clue that something is amiss–likely with the engine, but possibly with the transmission. If the CEL is illuminated, you need to have the stored trouble codes read.

Please check your maintenance records and come back to this thread to report back to us regarding maintenance history and also anything pertinent regarding the CEL.