Ok....First post. This is the scenario...94 K1500 4x4 5.7 TBI 214,000 mi.

I had vibrations in the tranny during acceleration from first to second and a clunking in OD while pulling a light hill. Replaced tranny (4L60e).
Shifting is super smooth and still have the clunking while accelerating up a slight incline. Can't figure this out. I went and replaced the cap, rotor and button. Same thing. Replaced Ignition coil (original at 214,000 miles figured I'd treat her for only $26). This tranny has no TV cable. It almost acts as though it's trying to shift down to 3rd while pulling a hill but can't make up it's mind.

What's telling the tranny to downshift? I know the ECM tells it, but what tells the ECM to shift down? Is it the throttle position sensor?

Any help would be appreciated. Thanks.

Could this also be a misfire causing the stumble? No codes in the computer either.

 

Is it a dull thump like an internal valve that is shifting back and forth or a sharp knock? With the vibration and the noise, have you checked the flex plate? It may be cracked and vibrating.

Dave

 

May want to check the motor and transmission mounts also

 

I had clunking going on while shifting and while going from a stopped position to slow acceleration. The ujoints were bad and the trans mount was wore out. replaced them and everything was good.