96 Express Van with a strange problem

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?

Reply to
Ken Gremillion
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Ken, Something is loose, be it the rearend, transmission, something. Check your driveshaft with the vehicle in park, on a flat surface. Try turning it back and forth, if everything turns together, but you get alot of movement in the rearend, then its the rearend. If the driveshaft turns, but the pinion going into the rearend doesnt turn, or the driveshaft turns farther than at the tranny or rearend, then its a bad U-joint. The clunk is caused from something catching up to something else. Atleast thats what it sounds like.

Reply to
pkurtz2

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