When driving down the road if i give it medium to heavy throttle when it gets to around 55-60 it just starts shaking violently (sp?) so much that i have to get off the throttle and it feels like it has lost alot of power. BUT when i let off the throttle i can not feel it doing it anymore. So i let it slow down until about 50 or so and it i get back on the throttle REALLY light it will go past 55-60 without doing it. I thought it might be missing but i has not thrown any codes of any sort. It has been doing this for a little over a year but before it would only do it at like 70 and i would never go 70 so i would forget about it. HELP!! it is getting anoying. The more that it does the more it feels like the motor. Because the last few times it has done it I started paying attention to it more and i can hear a different tone from the exhaust.

it is a 99 2dr tahoe

 

If you touch the brake does it stop? What about if you are not in overdrive? My initial thought is a bad torque converter but that would be a pretty hard call without actually feeling it. What condition is the ignition system?

 

well transmission was rebuilt in i think March. Never tried touching the breaks will try that tomorrow. How am i suppose to check the condition of the ignition system

 

New does not mean good. What quality parts did they use? How old are they plugs, wires, cap and rotor. Also if it is misfiring it would have to be a mis that is hard enough to damage the cat converter to turn on the light

 

I replaced the plugs a couple of weeks ago, caps, rotor and wires about 40,000 miles ago

 

I would rule out a bad plug or even a weak fuel pump. A clogged fuel filter could also act this way. I think MDTAHOE jumped the gun a little on the torque convertor. I think hes on the right track with an ignition issue or a fuel issue.

 

make sure to check all the motor and trans mounts