Strange Vibration When Cruising In 80-90 Km/h

[St Thicket]

Have anyone ever noticed a strange vibration when cruising in 80-90 km/h (50-56 mph)?

This has happened to me a couple of times, and it is more like resonance from something vibrating that actual mechanical vibration from i.e. gearbox or wheels. When I slow down it disappears, and it might not appear again when cruising speed is regained... really strange! Could it be a plastic cover underneath the car that starts vibrating?

I have the 2004 pre-facelift E12 with automatic transmission.

Any feedback would be much appreciated!

[KPARRIS-JONES]

Do automatics still have torque converters? If they do then I doubt it's the gearbox, and the plastic cover under the car sounds like the most likely problem.

Get her up on axel stands and tighten up the cover, then see if the problem still occurs.

[St Thicket]

Do automatics still have torque converters?

Mine do... I don't have the MMT (which suck bigtime).

Anyway, thanks. I'll see what I can do with the plastic covers.