hey guys, i rebuilt my t5 transmission installed a new stock replacement clutch, and had new heavy duty u joints put on the drive shaft, now i have this wicked vibration at 75mph to 85mph, anything over it's quiet and smooth, i push the clutch in still vibrates, 4th or 5th gear still vibrates, tires are ok and aligned, could it be the heavy duty u joints?

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86 Camaro with 88 305 LB9 using 86 carb setup, edelbrock performer manifold, 305 S/R Torquer Heads, Hedman Headers, Crane Compucam 2032 edelbrock cat-back, gutted cat, slp underdrive pulley, mallory ignition, 305 h.o dual snorkel air cleaner, hypertech thermomaster chip,160 degree thermostat, 5-speed, 3.23 posi

95 Beretta Z26, 3100 V6, 4 Speed auto, stock