1st Gen 5.2 4x4 auto. When we're excellerating quickly the truck shudders and hesitates. There is no heavy thunk when it shifts. When you drive slowly there is no shudder and it shifts smoothly. This happens from 1-2 and from 2-3 although not as noticeably. Any suggestions as to what the problem may be?

 

Shudder makes me think the transmission is slipping. How's the fluid level in the transmission (check it right after its been driven a while, and leave it idling, in neutral or park)? When you pull the dipstick to check the level, note the fluid color. Is it red, or dark, like a really dark red/maroon? Also does it have a burnt odor? Good transmission fluid is bright red and has only a slight oily smell. Fluid that's been overheated is dark and has a stronger burnt odor.

If its too low, add fluid and test it. If it's burnt, that's a sign that the trans has been stressed and may be damaged. How many miles on it?

 

not to say transmission isn't the problem but I had that issue when I got my 92 way back when , I took it to an old school transmission guy here.. been doing transmissions before I was born (over 40 years) with very similar issues... he adjusted the TV cable since it was way out, then told me to change the plugs and wire(tune up) and all will be good... haha I was since everything was new.. ended up swapping all again and either had a bad wire or a plug...