Surging/rubbing noise

[Erfan]

On half throttle I'm getting a surging/rubbing noise that I can't identify. It is intermittent and sounds like if your power steering fluid is low and you go around a corner but my level is fine. Cant see any belt wear/rubbing anything either. I haven't been able to replicate noise via revving with bonnet up, only whilst moving. I know it's a crap description but any assistance is appreciated! Thanks
W210 E300td

 

[Erfan]

Gearbox slipping?

 

[Stratman]

Parking brake cable rubbing on the propshaft?

 

[Erfan]

I couldn't see anything untoward in that area. Thanks for suggesting.

 

[Lyserman]

Try gently pressing on the parking brake pedal whilst the noise is occurring.
If it stops the noise, then the cable has popped out of a holding bracket allowing it to rub on the propshaft.

 

[Erfan]

Thank you for the useful tip