Hi, i have been told by my local garage that my gear box is about to go on my Cinquecento Sporting. The gears change and engage fine, but there is a grinding/knocking sound coming from underneathe the car (especially when i am accelerating). The engine sounds noisy too (rumbling alot). Anyway, my speedometer bounces between 0 and 120mph although i may be doing less then 60mph, i never get a true reading - are these connected??? Should i be looking at anything else? I reently had 4 new tyres put on my Cinq! Help greatly appreciated...