I have an 08 with two package too and bypassed my internal heat exchanger to avoid any chance of the transmission issues related to failure of that exchanger within the radiator.
Our trucks do have an additional cooler near the top of the radiator on the front on passenger side, but the lines still also feed into the exchanger in the radiator.
There is a thread here that I and others have posted to with instructions and pictures. The hardest part for me was mounting the new external cooler in front of the radiator. Took me a couple hours once I figured out what parts to buy /use.
So, just to clarify, are we saying with the tow package it's okay, good or advisable to bypass the additional factory aux trans cooler all together as well (rather than running the tru cool through the factory aux cooler and then directly into the trans, thus still bypassing the internal radiator one)? I hope to install my tru cool this morning but would like to double-check before doing so. Thanks all!
I did not bypass the additional heat exchanger. I just eliminated the one encased in the radiator.
I did the same thing last night after work. I have the tow package, and a pretty new radiator (last summer), but wanted a little peace of mind.
I bought 10' (he gave me the end of the roll, like 13') of 11/32" high-pressure hose from Autozone, and some fuel hose clamps. I bought two 4-packs of clamps in case I need to double-clamp the hose, but it seems to be OK for now.
It was very straightforward.... I pulled off the grill, and skid plate, and simply replaced the factory hard/soft lines with the new hose. I ran the hose from the transmission hard lines directly to the cooler, and back. The bypassed heat exchanger (it's not a cooler like so many people think) is drained out, and just exists as an empty chamber under the radiator now.
Trans temps are unchanged, and I didn't notice that it took any longer to get the fluid up to its normal temps.