Chrysler Repair: Chrysler LHS trans makes a humm sound. What to do?, engine oil dipstick, 2000 chrysler lhs

Question
I have a 2000 Chrysler LHS and while driving on the expressway, I inadvertently had the shift gear in 3rd.  The car has had an odd sound now since then when I am accelerating when first driving the car, kind of a humm until it gets up to the speed I am getting to.  It has not affected the car other than that, it does not sound any different when driving normally, just when I first accelerate.  It sounds a little like a 4 cylinder car.  The speed is good and the car seems to run fine but I am wondering about this sound.  

Answer
Hi Bea,
I don't think that driving in 3rd instead of overdrive would have caused any damage. Humm's are hard to diagnose, even when you are right there to hear them so I can't offer much on that score.
I would check the fluid level in the trans (see below) via its separate dip stick (located on the driver's side of the engine but further back than the engine oil dipstick), and also listen while the engine is idling and you have the hood open to try and localize any humm sound.  If you need trans fluid get a quart from the Chrysler dealer specifying that you have the 2000 LHS to make sure you get the correct fluid.
Checking the level: With the trans warmed up and the engine idling and the trans in Park, check the level on the trans dipstick. If it is in the proper area for warm (hot) fluid then you are fine. If you need to add, do a little at a time through the dipstick pipe but be careful not to overfill it.
Other than that, watchful waiting may be the best approach. If you know a competent independent trans shop you might ask them to go for a short drive so they can listen. But be aware that these trans's are very expensive to repair so  I would not let anyone who is unknowledgeable or unethical work on it.
It is possible that if there is something wrong that the transmission control unit has a coded message stored in its memory that will say what might be wrong (a fault code). The trans shop or dealer can attach a readout box to an under dash receptacle and electronically read that memory and tell you if there are any such codes. Ask them if so to tell you the fault code number, name, what it means, what might be the repair possibilities and costs. Then write me back and we can compare notes with the Chrysler shop manual.  If there are no codes, then I would believe there is nothing wrong. There readout should cost $50 or less.
Roland