strange transmission sounds.
 

my 96 has a rebuilt transmission in it with some aftermarket goodies it only has about 5000 miles on the rebuild. these symptoms have been happening for a while figured it was time to ask about it. when in park, if i shift into reverse it makes a very clear loud clang when it engages it makes the same noise going into drive just not as loud. the trans shifts nice good and firm doesnt slip or anything. any info would be great!
thanks

I would check the u-joints, front and back to start off. Or you could check the motor mounts as well. One of my friends was having that issue with his Duramax, and it turned out that it was his motor mounts.

Start off with checking those, cause to me it sounds like there's something loose in the drive train, and I would doubt very much that it's internal to the tranny.

Also, how high is your idle? that could also be a cause that would make a clink when you put it in gear.

I checked all my u joints but only by hand I'm sure they could still be bad. My idle is at 750