Driving Issues

Why does my 2003 VW Jetta 1.8T shake and rumble as I step on the gas pedal? When I am going faster I notice the car starts to rumble and shake, and when I let go of the pedal it stops. It felt like a flat tire at first, but they wheels were fine. I did have the wheels balanced but it didnt seem to help. Why does it shake an rumble so much??

First blush are the 2 front half shafts (axles). RH one comes out of RH side of transnmission and goes to RF wheel; vice versa for LH one. Each axle is essentially 5 elements (not actually, but for the sake of explanation): shaft coming out of transmission; flexable joint that connects first shaft to second longer shaft; another joint that connects the longer shaft to a shorter shaft which goes through hole in wheel

bearing which is firmly attached to wheel. The joints are supposed to turn and flex as you turn steering wheel and go over bumps but w/age they start to bind, or if there’s wear (play); the looseness causes vibration especially during acceleration- your symptom. Tell your garage the symptoms you’ve just posted (and by the way it was a very good description), and also that wheels have been balanced (which ones, by the way?); and that you think it could be halshafts. Good luck and please post back.