ok heres the story.i have a 2000 blazer 4x4 auto.my sun shell gear went out about 2 months ago.i had the tranny rebuilt and i finished putting it back in sunday...everything was going fine sunday night untill about 30 mins of driving when i noticed that when i hit 35 to 40 mph there was a vibration coming under the car.i cant figure out where its coming from..i thought maybe it was the u-joints so i replaced them today.i got up to 35 to 40 mph and once again the vibration...does anybody know what this could be?!?!?

 

i figured out what it was....

 

And it was???

 

He left the wrench in the transmission

 

My neighbor had the same problem with her 00 4x4 4 dr blazer, it was a lack of transfer case fluid.