Assuming you have a crew cab Laramie 4x4 and a rear axle ratio of 3.92, then you're rated to have a max towing capacity of 4450#. More details would give you a better answer. Also, you could Google the towing charts.
As far as a transmission cooler goes, I would say that if you are towing a 3500# trailer once in a while, then you probably don't need the cooler. If you're a landscaper and pulling it all the time, then yes you should get one. Other factors like where you live and the terrain could play into it. But, the truck is rated to tow that without problem anywhere as long as you're willing to slow down. Having the cooler is good insurance in general.
As far as a transmission cooler goes, I would say that if you are towing a 3500# trailer once in a while, then you probably don't need the cooler. If you're a landscaper and pulling it all the time, then yes you should get one. Other factors like where you live and the terrain could play into it. But, the truck is rated to tow that without problem anywhere as long as you're willing to slow down. Having the cooler is good insurance in general.
