My guess is its transmission as it stops when you take your foot off the gas.
I have heard drumming noises in the past from the rear diff on a friends car. Could also be gearbox or transfer box, transfer boxes are problematic on these cars. If your sure its coming from the back check your diff oil level, just fill with ep75-90 till it runs out the plug hole. think it takes just under a litre from empty.
Could be tyres though, I have the that problem on my wifes fiesta, but is their all the time on her car. Richy
Last edited by Richy; 25th March 2020 at 07:22.