isolating road vibration sources
 

after finally eliminating wheel balance as a factor (had a dynamic load balance performed), i now see that there were other components to the vibration i was experiencing at 75 - 80. certain types of road seem to induce it while on smooth blacktop, the vibration is non-existent. it is a very slight vibration you can feel through the body and somewhat on the steering wheel. is this indicative of front-end component wear? what would be a likely culprit? i thought about the flex disk, tranny mount and engine mounts, are those possible sources too? at one point i thought that it happened when under load such as on an upgrade but my observations were not conclusive.

any ideas on where to start?

I had a similar problem that was eliminated by replacing worn out lower front balljoints.- Did the Idler Arm bushing kit at the same time to finally free the world of annoying grinding steering wheel noise (when turning wheel to right).
hope this helps.

My 126 runs well on smooth surfaces but vibrates when on rough. It vibrates more than usual but real smooth if the road's good. I changed all the front bushings and had the wheels balanced. I thought it could have been the drive shaft but am now thinking that its just normal.

One way to find out if your engine mountings need replacing is to step on the brake with the engine on, and engage into D or R and feel the vibes. If it vibrates badly, then perhaps the mounts have to go.