After driving for a while when I go to back the car into a parking spot(backing or driving very slow and turning at same time) my rear end (posi with 273 gears) makes awful clunking sounds.
Is this normal or is there something wrong?

 

Put one or two bottles of GM Posi Additive in with gear oil.

 

Sure it's not a broken tranny mount?

 

mine does it too, he needs to add the gm diff additive, mine didn't start doing it untill i changed fluid, and on suggestion from a friend used a full synthetic fluid that claimed i wouldn't need the additive,

and i know my torque arm and trans mounts are good, cuz that was my first thought too

 

Mine does the same thing but it's only noticed at low speeds or while turning at low speeds, I changed my fluid twice and added posi additive, both times and still does it. any thoughts on this?

 

Maybe the clutches in your posi are blown, that could make the clunking sound since the clutches are also like shims and when they get worn down it gives play between your axle and the c clip. The additive is a for friction and that could cause it but you would have to have a lot of friction back there for it to make sounds like that.

 

MY car does that after i added an auburn posi unit and 3:73 gears
it make a horrible banging noise when i start out slow and when i turn slow.Once pick up speed it goes away.When it bangs you can definatly feel it.You get loud thunk sound and it does come the rear.........

 

Any other ideas what it could be????????

 

do u hae enough fluid in the rear, and u need posi additive also.
i have never done a rear gear swap but it is possible that maybe something is lose or put on wrong. I had to change a front bearning on my moms chevy astro van and i put everything back on right and tighten everything but now i have a wine in the rear at any speed. I know its put in right but it just makes a noise now!

o well not my car

 

Heres a update i changed the fluid in my rear end(MOBIL 1 and POSI ADDITIVE) and the clunking stopped in the rear end