Re: transmission problem on a 02 grand cherokee overland
So then first thing to do is checking if the oval inlet filter is detached or not. When installing this filter in the oil pump inlet, with the seal installed on the filter neck, it has a good change of getting loose again and the pump will only suck air. Depending on how long it was running like this (with the filter detached), severe transmission damage could result.
So have a look in there and be sure that the oval filter seal will be installed first in the oil pump inlet (with the help of the butt end of a hammer or alike) and that then the filter neck will be inserted in the seal.