Having just serviced my ZF transmission and installed an air-to-oil transmission cooler with a fan, the following is a write up of how I approached it.Some of information out there was very scattered or hard to find, so I thought a full write up might help anyone else doing this. This should bring together the whole job of adding a cooler to replace the factory heat exchanger, adding a fan with a thermostatic switch to activate (plus a manual override), flushing the ZF, changing the filter