Transmission Hesitation

Hello
I'm not sure what's causing this problem
when my truck changes to 6th gear I feel a slight jerk in my seat when I'm pressing the gas pedal if I press the pedal harder it doesn't jerk as hard
but sometimes when I don't press the gas pedal it feels very smooth
and sometimes its a very hard jerk and clunk noise
I'm not sure if the problem is from the rear end (driveshaft, transfer case? maybe low fluid or driveshaft needs lubing?)
or its from the transmission
just changed the Transmission fluid (I had the problem before changing it) but I don't think there is any improvement

 

Have the transmission fluid level checked first, before anything... if its low that may be your problem...

 

I agree with blackdemon_tt especially if you notice it on down shift when coming to a inclined stop.

 

Update...
solved the problem
Transfer case fluid was low due to a leakage just added some fluid and the problem went away