clunking and jerking when move forward and backwards

2000 blazer,had transmission put in 2yr ago..when i take off at any speed i get a clunking like somethings is engaging or kinda slamming doesnt when i back up too..tranny shifts ok..u-joints seem ok was wondering if it mite be something in transmission after i start going it will stop but when i start to slow down it does again and again on take off..kinda violent slamming

2W or 4W?

Does it clunk when it shifts or just first put in gear?
Any clunk in put into reverse?

Any check engine lights or codes?

2wd.chek lite was already on...no clunking when it shifts and yes it does it in reverse,wonder if its the tourqe convertor,gettig progressively worse

Check the universal joints on your drive shaft.

the u-joints seem ok...

2wd.chek lite was already on...no clunking when it shifts and yes it does it in reverse,wonder if its the tourqe convertor,gettig progressively worse

Check for drive line slack and looseness as already said.
And also engine and transmission mounts.
Is the engine idle normal or fast?

Why do you think it is converter?

If check lights are on check for codes and post back codes.

the u-joints seem ok...
How did you check the U-Joints?