Okay guys whenever I shift into reverse. I get a loud CLUNK as it goes into gear. This is the only gear I get this clunk in...

I just flushed the transmission and replaced filter.
A week before I changed the fluid in the rear diff as well.

Would this be more of a trani or diff issue?

Also, If i don't have enough information to help decide, any ideas on where to troubleshoot would be appreciated.

 

Check u-joints.

 

check ALL of you U-Joints...

 

If anyone hasn't already suggested it, the u-joints are the most likely culprit.

 

Not sure if you read what everyone else said, but yes that is what I am going to look into next. Thanks.