I bought a 1997 GSX 5 speed with low miles and a bad motor. I replaced the motor and everything has been going smooth except one thing. There is a terrible vibration when in power (around 3500 - 4500 RPM's) it has the stock t-25 so it's at full boost when floored. I've checked the u-joints and carrier bearings with nothing unusual. The rear diff bushings are also good I can barely even budge the diff while using a pry bar. Also has a clunk if you let out the clutch fast, not launching but just letting it out quick. Is there a way to see if the differential is bad? Thanks in advance.