I have a 2001 ram 1500 with the off road package, and every time I take off from a stop I hear a load thunk noise coming from the rear end. any ideals on what it is?

 

U-joints in your drive shaft would be my first thought. Crawl under there (with the truck off) and see if you can turn the shaft at all by hand.

 

i second that motion... unjoints would be the first place to start looking...my rear ujoint was horibbly bad and made the truck vibrate when id drive... but before that it would do the same thing ,, clunk when you put it in drive/start from a dead stop. .. i checked the ujoint often and i couldnt tell if there was play in the u joints but they were bad anyway... the aft ujoint had a cap with NO needle bearings left in it lol.....

the best way to check would be chock the wheels (front ones) and put the truck in neutral, climb underneath, twist the drive shaft with one hand and twist the companion flange with the other so you can see if it plays between the two where the ujoint is...

like this pic

do it the same way but at the forward end of the drive shaft

[IMG]local://upfiles/3936/910AFBC5F4144565A0089E642F37411D.jpg[/IMG]

 

Another good way to tell if your u-joint is toast is like the others said, grab on both sides. And move up and down. Good way to tell if you have pinion yoke play as well. If they have movement up and down (like side to side) then they need replacing