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I just upgraded my tires from the stock 31x10.5's to 17" rims and 285-70R17 tires. Looks Bad @ss!! Truck is a '98, 160K miles, supercharged with the URD fuel system upgrades, so power is not a problem.

My question is around towing. I took a trip up the N Cascades highway and the tranny temp (aftermarket gauge) ran quite hot, peaking at about 260* for a couple of minutes. Luckily the pass flattened out and I was able to get the torque converter to lock up and it quickly cooled back to 180. The A/T temp light did NOT come on. The truck was essentially unloaded, but made me quite concerned for what might happen in warmer weather as this was a cool day (not more than 60F), and I'm likely to make the other trips with several hundred pounds of gear, and eventually a small travel trailer, and I'd like the truck to live through it...

I do have an aux tranny cooler on it, but probably not optimally mounted-about 1/4 blocked behind the front license (which I'll relocate this weekend), and I could drill some holes in the lower bumper fascia to increase airflow through there also.

The pass is too curvy to keep it consistently above 50 mph to keep the converter locked, so increased heat is likely unavoidable.

What would my best options be? Re-gear the diff's? I still have the stock 3.91's. I could add a 2nd tranny cooler on the drivers size to increase the cooling that way, has anyone done that?

If any of you done towing with similar tire size/gear ratios I'd like to know how you kept things cool going uphill and avoided cooking your tranny.

Thanks!
 

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You definitely need to regear to get your powerband back. 4.88's should get you up the hill much better than the 3.91's.
 
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