Transmission problem maybe?

I have a 06 tacoma v6 dbl-cab with 115,000 miles. I have never change the transmission fluid. I have heard many different opinions concerning changing the transmission fluid in toyotas.

My problem: I have had vibrations/shaking/shimmy when driving up hill at low RPM's. I have counted the gears when driving up hill and the shaking starts when it is either shifting from 4th to 5th or 5th to 6th gear. (only when it is under 1,500 rpm's.) when it starts to shake i accelerate and the vibration stops, as if i forced it to shift. to diagnose the issue i put my truck in 4th gear and started at the bottom of the hill and no shaking...wtf? it only happens when i leave it in "D"

I have replaced all the u-joints and had the driveshaft re-balanced. Vibration has calmed down but not stopped totally.

Also, when driving at about 45mph my truck seems to be confused... its like it has trouble figuring out what gear to be in... idk it may be me being paranoid.

Can it be the transmission? Can it be the shift solenoids? Can it be my torque converter? Can it be the clutch? Transmission mounts?

(Someone said to change the transmission fluid and it should stop??? The trans fluid is a dark black/brown color... and I have also heard if I have never changed the fluid, do not change it... I can ruin my transmission.)

 

I see you posted another thread..
http://www.tacomaworld.com/forum/2n...-joints-balanced-driveshaft-transmission.html

 

Yeah!!! You caught me. This problem is annoying me and I want to solve it. Ha
I am going to take it to a local shop today and discuss options.
Thank you!