Humming Dif

[K5Psycho]

ok i just put in my 700r4 on my 87 blazer and i took it on I40 around 45 to 70 MPH i hear a himming sound from the back of truck i am thinking if it is the U joints or the dif
also around 70mph it starts to vibrate alot ? any thoughts let me know
thanks

 

[Sandman]

U-joints would be the first thing to look at. Mabey double check all of the bolts. I know I've missed them.

 

[K5Psycho]

what?