93 4runner A/T shifting

My 93 4runner started shifting strange. It sometimes doesn't go into
overdrive and sometimes downshifts when it isn't needed. I'm just
wondering if there's a common cause for this. The kickdown cable doesn't
seem to be sticking. I've noticed the problem more when the thing has
warmed up. It could have been doing this for awhile. My wife drives it
mostly and its done this to me a few times. I have her keeping an eye on
the tach now. Once, I lighty hit the gas at 40 and had the thing kick up
to 4500 rpms. I know it shouldn't kickdown that easy. I guess I'll try
to pull some codes when she gets home from work with it.