Boy I've got a wierd one for you guys. I've got a 96 Express Van (G1500)
with a 305 V8 and 130K Miles. I first noticed this problem when cruising
at 60 on the highway (on cruise control). I topped a very slight incline
into a slight downhill segment of the road. As the cruise went from
accel through float, and into decell, there was a single jerk. It was
rather abrupt and I actually thought I had hit something. For the next
hour I tried to duplicate this (chuggle, bobble...). I could duplicate
it under the same conditions (cruise, over 55mph, hill, slight
downgrade). I was finally able to duplicate without cruise control, but
all of the other conditions had to be the same. It would only do it with
a very slight movement of the pedal. My first thought was broken motor
mount. I checked them over, and found a disentegrated trans mount.
Great, I thought, fixed. Bzzzzzzt, wrong. It won't do it when I
accellerate hard, and just release the throttle. It won't do it unless I
am on a slight downgrade, steep downgrade won't do it. Oh, no codes
either. Any Ideas?