help 92 300sl bad vibrations

[greghskj]

my 92 300sl has developed a vibration at 80 mph and faster,I talked to a mercedes mech. and he said some sl's are hard to get the tires balanced so i have had them balanced by 3 different stores,still no change. even tried new tires.it feels like its worse at the right rear, the front seems fine. it almost feels like a bent axle.is their a way I can check to see if the axle is bent. thanks for any help or ideas....