You sound like your doing alot of guessing on your actual weights. Your concern on transmission life is valid. Yet without knowing what your actual weights are is just wishfull thinking. Go to scales get your tow vehicles and trailer weight, then go back with just your tow vehicle. And get the weight of what you got on the trailer. You may be shocked at how quickly it all adds up. Those numbers on glove box are real. Your H2 is built on an HD chassis. Are you sure about 4L65, not a 4L80 or 85 ? Thats what the RPO code is? Unless it's 100 % synthetic, regular mineral oil trans fluid begins to breakdown at and over 210 to 220 degrees F. What does the Owners handbook say about trans temp gauge monitoring when towing? Good luck.
Guessing? No. Estimating? Sure. My numbers are based off the added equipment on the H2 paired with the weight my ski boat + trailer says on it. The truck is an overestimation and the trailer, while knowing the exact weight, I'm rounding it up to 5000lbs which is 430 lbs more than I should be counting. Better to be overprepared. I mentioned 4L65e previously, but I stand corrected. It is equipped with a 4L60e, I got the transmission mixed up with the one in my truck. How I know this? While the RPO codes in the glovebox would confirm the transmission, the pan shape is the more accurate way to tell. And yes, it is a 60e/65e pan. Either way you skin it, they're not the best transmission.
Funny part about the owners manual is it makes zero mention about transmission temp monitoring while towing. It's like the people writing the book completely forgot the gauge was there. On top of that it also states that when driving on grades it is OK to leave the truck in D, which is just laughable in my opinion.
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In general I'm noticing we're getting off-track from the original question. This thread wasn't to start a discussion on transmission coolers or the truck set-up. I appreciate the feedback on both but I was just curious to know if a cold side bypass is necessary if I am retaining the OEM transmission cooler routing (through the rad, to the ext. cooler, back to the trans). To give a little background, the truck will see occasional (occasional as in maybe 1-2 months a year) sub 30*F temperatures and I just want to ensure the transmission would properly heat up to 180*F without the bypass. I appreciate the feedback from
@Frank Enstein and
@Schurkey regarding this matter. Any other feedback on the cold bypass is welcome.