Disco 2 Issues when going up hill.

Hi i have a 2003 Discovery td5 auto which has developed a smell of hot oil whenever I go up a steep hill. Also when going up a steep hill it will only get upto 30mph and 3k rpm and then the engine revs will fluctuate even though i have my foot held steady on the throttle, it’s almost as if it’s trying to change gear but can’t.
Any help or advice would be gratefully received, many thanks.

Leaky exhaust manifold ?

Really need codes reading to stop the hunt and peck search for faults, that said a check for split, cracking and delaminating hoses won't go amiss ...

Your exhaust manifold probs needs a new gasket and to be skimmed

Could also be the auto transmission overheating. If the oil smell is ATF it is quite distinctive (sickly)

Hi i did think maybe it was a problem with the transmission, i have the gear box oil and filter changed but made no difference.