Strange noise when setting of on hill

When setting off on an a hill or under load the car makes a vibrating noise and the revs drop below 1 but once set of runs no problem the noise was followed by a smell of rotten eggs this has happened a couple of times now

Ford grand cmax 2012
27000 miles



Smell of rotten egg means there is something wrong with the catalytic converter.

Thanks for your reply mate very helpful

Thanks mate not sure to be fair not had the smell since could just be my driving style thank you for your advice

It may be some kind of transmission problem. Suggest to check the fluid level as a start. If a manual transmission, could be a clutch problem. Seems unlikely to be a cat problem at 27K miles, unless you’ve had some misfiring going on for some time. Any diagnostic codes? Starting off uphill with a cold engine is hard on any car.

And all this time I thought that was why vehicles had low gears. Modern vehicles only need a few seconds before they are ready for anything but 1/4 mile time trials.