Down shift clunk sound?????

[onefastgn]

When it down shifts when i am stopping i feel a clunk. I'm not real sure if it is coming from the rear end or the Trans. Everything seem to shift fine under load or just cruising except when it shifts back down by it's self when i start to come to a stop. It happens from 2nd gear to first. The trans is a Vince Janis trans stage two. and i just changed the gear lube in the rear.( Yes i used the additive) What do you think it could be. It does shift a lot harder then the stock one did and i also just changed the U-joints. Thanks for any help

 

[77 cruiser]

The clunk is probably the 3-2 band is coming on a too harsh, no cushion spring on the servo. You really won't feel the 2-1 unless you select manual LO.