I've done a fair bit of searching on this, but I haven't found quite what I'm looking for. We'll be taking the F250 loaded up with 2800 lb. camper on 6k trip shortly. I want to change the transmission, transfer case and rear diff fluids before we go. My ZF-5 has the usual roll-over noise, but shifts fine. So what readily available fluids do you recommend? Is the newest Mercon the best for the tranny and T-case? Rear diff-wise, what works best? After this trip, we will be pulling a 12k enclosed gooseneck across country, so I want something that will stand up to heat as it will be to Florida in the summer. And yes, I'd prefer to go all synthetic. Truck has 166k now, 4.10 Sterling LS.