1999 Transmission problem

Hi everyone,

I've got a 1999 Tacoma Prerunner, 2WD, V6, 3.4L, 118,000 miles, with an automatic transmission. The thing won't go backwards (with the engine running). When I shift into reverse, the truck just acts like it's in park, and when I shift into neutral, it acts like it's in drive. I haven't been able to figure out what's causing the problem (it's not giving me any codes at the moment) and want to know if it's time for me to take it to a transmission guy and pay out the butt to have it fixed, or if there is something simple that I haven't thought of yet.

Things I've tried so far:
-changing the transmission filter
-assuring that the linkage from the shift lever to the transmission is working correctly
-got a new TPS and adjusted it (old one was throwing codes and adjusting it didn't help)
-cleaned the mass air flow (only because it was throwing codes)

Thanks in advance for any help.

 

The shift linkage might be out of adjustment .