Transmission Vibration

[DJ19885.0]

My ranger has been converted to a T-5 transmission, and at 70-80 mph it has a bad vibration that comes through the shifter AKA the transmission is vibrating. It is not a wheel weight vibration ( know what those feel like) and I did check play in the u-joints with the trans in neutral and they felt tight, I couldn't feel any play. There is also 3 weights on the driveshaft, but I have never heard of these actually coming off so I assume the shaft itself is balanced, but I cannot be 100% as I have no way of knowing if it always had this issue or not (just got the truck together and driving). I did notice that I could push the trans up and down a good inch with about 30lbs of force. It looks like the bushings on the frame that connect the trans brace may be allowing this movement. Is it possible that this is the only reason for the vibration?

Thanks!

 

[DJ19885.0]

UPDATE - Upon further inspection, I found that the splined end of the driveshaft that goes into the transmission has a little play between the shaft and the transmission, which does not seem normal. I can move it around and it makes a bit of clunking sounds. How is this fixed?