Transmission problems

I have a 99 Tacoma 3.4 v6 automatic trans. And it's acting like it's getting stuck in between gears and wont go in to reverse and it won't shift gears all the time while driving at speeds. Any help on where to start would be greatly appreciated

 

Have you checked your fluid level with the engine running?

 

yep, fluid level and quality is good place to start. This trans is electronicaly controlled and it sounds like you have some sticky valves in the valve body due to either old fluid or an coolant/trans fluid intermix. The issue in my opinion now comes down to luck. What I mean by that is if you dump the pan and replace all of the fluid at once you could get lucky and not have a bigger issue. I prefer to replace fluid on auto transmissions that have not ever been maintained, gradually... one or 2 quarts at a time. Figure out which trans line is the output of the trans to the cooler on the radiator and run a quart or 2 out of her and refill with new, next week do another 2 quarts. Of course this is just me, other peeps will have different opinions and will have different experiences/outcomes.

 

Just did a transmission drain and fill as well as replaced the filter and put new gasket.

Also added a transmission oil cooler and a filter. I'm hoping it keeps running until I can get an automatic 4x4 tranny to rebuild.

196k miles and has never been replaced before.