don't know what to make of it
 

i just had my 383 lt1 stroker done and to go along with my motor i went with a built 4l60e. i was driving the car to break it in and there was a horrible vibration, thought it was a u-joint but apparently the shaft in the transmission is moving, is my trans shot? it shifted perfected with no slips or anything, just a really bad vibration. input is needed. thanks

what do you mean the shaft in your trans moving do you mean its moving in the tail housing ?

im not an expert on transmissions, but its the shaft that goes into the driveshaft. i hope this helps

well it will move if the driveshaft is not in there its supported by the yoke on the drive shaft which in turn is supported by the tail housing bushing. Now if the yoke of the drive shaft is wobbling excessivly in the tail housing remove the tail housing and inspect the bushing in the tail .

i think i know what you mean, is it the 4 blot ending of it? im taking it to a tranny shop so do you think they will know whats wrong? do you think it will cost a lot to fix?

Im sure they will and it shouldnt cost much ,let me know what they find

will do thanks a ton

could the play be causing the shaking of the car?

well if theres alot yes for instance if the yoke is worn out or the bushing in the tail has excesive wear, But it could also be many other external issues also dealing with the drive train and drive shaft.