96 Express with 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
KENG
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i'm not sure what cruis controle system you have. could be a sticky speedo cable. if your sure its not the cruis controle you could look at your vacume advance or the mechincal advance return springs under the cap, could be a carb issue if it has one, could also be a dirty or clogged injector.... no way to tell from here.

Reply to
dirtdude

No 1996 GM Vehicles have Carburetors. They are all Fuel Injected, Including Medium Duty Trucks. Charles

Reply to
Charles Bendig

Has the transmission had a fluid & filter change? If not it is past the service interval for such. Charles

Reply to
Charles Bendig

ATF and filter have been changed 3 times, once at the first oil change to Full Synthetic, then once at about 65K, then again when I replaced the trans mount.

KenG

Charles Bendig wrote:

Reply to
KENG

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