Rough vibration up hill...

possibly the cv joints are going bad

engine light flashing means a problem needs immediate attention ----have the vehicle scanned most auto stores offer this service for free more than likely the viberation is what is setting off code

Check transmission fluid in g/box is not burnt Re: Jeff

look for play or binding in the universal joints

is the transmission slipping?electronic controlled transmissions go into fail safe mode starting out in a higher gear

the brakes vibrating could mean a rough spot on the disc, a warped disc or faulty ABS.

check out harmonic balancer .

IF GEAR SHIFT SHAKES THEN THE TRANSMISSION MOUNTS COULD BE BAD. HOPE THIS HELPS. GOOD LUCK

your highway acceleration problem could be a coil problem. Not sure if that year of chev has coil packs or not but experienced same thing with ford 5.4L. went through 3 coil packs and did the same thing each time before biting the dust. Transmission seems to be sticking on the 1to2 upshift and could be a sticking solenoid in the valve body of the tranny. If the shifting problem persists then the tranny deffinately has to be rebuilt. It's made it quite far if tha is the original tranny, you cant expect too much life out of it if it has been worked hard. I highly doubt a fluid change would help at all. Or if you want, you can buy a can of new truck from GM for about 25 to 35 thousand bucks! Typically works great!

you may also want to consider that the coil pack is failing... i remember when my windstar coilpack failed i had an awful time just getting up a small hill... can't recall if it shuddered tho.

Robert