I have a E350 with a 460 and it has a tendency to heat up on grades. It is stock with the stock trans, oil and power steering coolers. I'm think about adding another trans cooler. I can't decide to...
You say it's heating up on grades but WHAT exactly is overheating? If it's the transmission then a larger cooler might help but that's not lilkely to help any if it's the engine that's overheating.