Mercury Sable Noises Thump

When Place In Reverse My Car Sometimes Have A Thump Noise/lurch What Can This Mean Is It The Mortor?

When You First Start Driving The Car, It Shakes But As You Pick Up Speed It Levels Off And Runs Ok. What Could That Be? When I Start...

I Recently Changed A Flat On My Car With A Used Tire And Now Its Still Making A Thumping Noise. What Can It Be? Bearings? Some One Said It...