electric or transmission? please help
 

I have a 98 C1500 ext. short bed, when i slow down, and it shift from 3rd gear to 2nd the truck shakes and vibrate for 2-3 seconds, the more i brake the more it vibrate at the point of down shifting, any ideas? Thanks

RE: electric or transmission? please help
 

I don't think it's transmission related, just coincidental on the downshifting. To confirm, next time you're slowing, put the tranny in Neutral and see if it does the same thing. If so, it's not your tranny. When's the last time you had your brakes worked on? You got ABS brakes? Could be an issue there. I would look to your wheels/brakes for first ideas.

RE: electric or transmission? please help
 

It sounds like the torque convertor is the problem. The torque convertor has a lock-up feature to save gas, preventing slipping when running a steady speed. If it isn't unlocking, as it should, then you will get a shudder at shifts and when braking.