Clunking sound

[Super6]

My trans in my car has about 30,000 miles on it since a buick dealer(car has 70,000 miles) built it before i bought the car. The car shifts good in second real firm. I played around with the detent cable one time and got it out of adjustment(shifting too fast) and it started flairing 2nd to 3rd shift. I got the detent staighten back out and it kept doing the flair for a while longer but it finally quit. I changed the fuild with type f and everything looked good in the pan, no metal shaving or anything in the pan. I have a b&m trans cooler on it to help keep it cool. I only drive the car about 2 times a month but when i back it out of my shop everynow and then when in reverse it will clunk. I have a slight upgrade(hill) when backing out of my shop. What could be causing this? It only does it once. ..............................................................thanks

 

[Super6]

Guess i won't worry too much since it is shifting better than it always has...........................................................

 

[J. C. Plemons]

Do you have Positraction? If so, that may be where your clunk is coming from. Mine sometimes does it if it has set for a few days.

 

[Super6]

Yes i do have a positive traction. Probably just the clutches in the posi. Thanks JC i haven't thought about that....................