Hi, I have a 99 Bravada, first off im getting 16-17 mpg so im thinking no fuel issues like spider, regulater, etc. It runs exellent when cold but as soon as it starts to heat up it jerks pretty hard from about 10 mph to 55 mph, the harder i hit the gas the harder it jerks. it jerks not in a pattern.. just about every 4-5 seconds.. The RPM's stay very steady and it idles exellent. and if i press on the brake and the gas and hold it at about 3000 rpm parked, it wont jerk..I have replaced cap and rotor but it had a full tune up in 2010 with only 5,000 miles since then..Im thinking its a trans/ trans case problem rather then engine. No CE light.. Awd works really good. I also have a 99 Envoy and ive tried transfering the coil and other sensors to try and diagnose the proplem but no luck... its really got me stumped..The trans pan leaks a bit, i plan on fluid change with filter and gasket but i dont think that a little leakage would cause the hard jerking.. please help, its really annoying me!! Maybe change the transfer case fluid with the blue stuff? i dont know if its ever been changed..

UPDATE AS OF TONIGHT; When i got off work i messed around under the hood unplugging various sensors (maf,map,at,tps,ect.) then driving it until everything was plugged back in the I opened the main fuse block and pulled the ATC (auto transfer case) BINGO!! the problem went away!!! Plugged the fuse in and drove it and the problem was back, and sometimes hopping and binding on turns, but my awd works excellent. BUT this is not good. The tires are all the same size but the rears have a lot more tread,but with it acting this way (working fine cold then heating up and binding/jerking) I think its time for some new auto-trak II fluid. And a new tranny pan gasket as this one leaks a little on the exhaust,also not good. lol