Engine mounts, transmission mounts, professional tuneup, spark plugs and coil packs tested engine runs perfectly at all speeds gas mileage is excellent when auto transmission shifts from 1st to 2nd under a light load there is a vibration I don’t have a clue and I don’t know what to do next does anyone have any ideas I would appreciate it?
I’d appreciate Any information to solve this problem

chefusa

 

in the things that rotate category you have axle shafts, wheel bearings, brake rotor/pads to go with engine/tranny mounts as well as accessories (AC/power steering/altnerator etc). There are also things that can vibrate (exhaust etc) because of engine speed. Do you get a sound with the vibration? where do you feel or sense the vibration (ie steering wheel, center console, seat/door sills?). Other than the upshift clue, does it seem to come from a location (left or right), change with roadspeed or turning/braking?

 

Could be torque converter shudder (squirt in a tube of LubeGard Instant Shudder Fixx (sic)). Probably not, but hey - for $7 and two minutes, it's seriously low-hanging fruit.

I'm also thinking engine / transmission mounts - you're going to feel the 1-2 shift more than the higher shifts (since there's more mechanical advantage trying to torque the engine around). Could have gotten a bad one, or maybe one wasn't tightened properly (not that a professional mechanic EVER misses anything). ;-)