Originally Posted by crispyboy
do you tow with the overdrive off or on?
Answer: It depends on the situation. By turning off "overdrive", you can compel the transmission not to upshift beyond 3rd. That's all there's to it.
You can see the "overdrive" button on the shifter at the upper right corner of the image.
Here's the shifter position for WJ Grand Cherokee: [Park - R - N - D - 2- 1]
[D] = (1st ~ upshift all the way to 5th)
[D with "overdrive" turned off] = (1st ~ upshift up to 3rd)
 = 1st, and upshift only to 2nd
 = 1st only
In some situation when the vehicle is traveling at some speed and the gas pedal is pressed on or let go off, the transmission may often hunt between the 3rd and 4th, or upshift and downshift unnecessarily, because the vehicle is not smart enough to know whether you're accelerating, pulling a trailer, climbing a hill, or about your next intended action.
I would turn off "overdrive" when climbing hills, or pulling a trailer, or pulling a trailer & climbing at the same time. You wouldn't want to the transmission to upshift too soon, just because you let go of the gas pedal momentarily.
However, there's nothing wrong with letting the vehicle to upshift to 4th or even 5th, when you're cruising with at highway speed with trailer on the flat prairie.
Generally, "overdrive" simply meant 4th during the days of 4-speed automatic. Nowadays with prevalence of 5 or 6-speed automatic, "overdrive" designation is not intuitive and is confusing. I think all recent cars and trucks equipped with 5 or 6-speed would allow the driver to sequentially select which gear to be in — i.e. +(plus) & - (minus) for upshift & downshift.