My transmission has been slipping lately, how can I find out if the bands can be adjusted?

The bands do not affect slipping. If the low / reverse band breaks, it will not stay in first gear when you put it there. It will still shift to second, and you wont have reverse.

Okay, what could be making the transmission slip?

Worn clutch plates is the most common, but if this came on suddenly and severely, a hardened and cracked rubber lip seal is just as likely. We see a lot of Ranger transmission failures. Good used ones can be hard to find and they are usually expensive, so we just send people to a transmission specialty shop for a second opinion.

How do you check to see if it is a faulty shift solenoid could be causing the slippage?

A non-functioning solenoid will result in a failure to shift to a different gear. Slipping will not be the symptom. The symptom will be it gets stuck in the wrong gear.