Well l've been to GM and now the guy at the Transmission shop is telling me its engine.....? All together these two places are still scratching there heads....

Hopefully a mount but i don't know....

About two weeks ago l hit a lift in the road ( highway..) it was about two inches high....l hit it at 140 kph....
I didn't notice the vibration then but l cant help but to think thats what caused it......

Nevertheless the vibration only appears around 4500rpm and will stay there through to red line.....it does it in every gear including reverse ( auto ) ....

The vibration does not come with any sort of sound or knock.... to make it simple l have a shake throughout the dash and steering wheel only when under load......

My uncle thinks that l hit the front passenger side engine mount...and the vibrantion is coming from there ( the front right)....Idunno....

I posted a post like this in the transmission forum last week but now that the transmission is out of the question....and he said it the engine or something related to the engine.......l found myself over here asking you guys on what internally could cause this type of shake....Keep in mind...

1) Only happens under load.....not coasting in neutral....
2) Because of the above it has nothing to do with tires and or rims

you took your car past 4500 rpms in reverse???

btw sounds like a possible month ide ave them check and get some aftermarket ones on there.