Unfortunately it sounds like your tranny is on the way out. The good news is that 165k miles is quite a good run, if it can be seen that way.

Once the oil (ATF) has oxidised and the damage is done, there's not too much that can be done. Does the tranny do this only when it warms up? If so, you could try a couple of things for cooler running or better atf high temp performance: this may or may not improve things.

The addition of an atf cooler (mod on my site, ozbrick.com) might increase the threshold before the tranny starts playing up.

You could install synthetic atf which has a higher temp tolerance. Apparently these boxes can get to much hotter temps than what standard dino dexron 2/3 can withstand, just in stressful conditions like city traffic. Redline states their pure synth atf is good to about 700 degrees which is above normal operating temps. Amsoil also does a good ATF, so I am told.

Redline also have a product, water wetter; it claims to reduce the temp of the cooling system significantly. I have bought a bottle to try but haven't put it in yet so can't say from experience, but if it does what they say then it could mean a cooler system overall which can thus keep your tranny cooler.

If all of that doesn't work, shop around for a rebuild; I have found a lot of variance in quotes here in Sydney, and presume that is the same everywhere.

good luck
michael/ozbrick.com