Originally Posted by dokaman
Thanks for the replies and information. This is such a stupid issue.
One more question about the 265/75/16 tires. With 3.55 gears and a 7.3l, would that hose my MPGs or towing? I plan on 4.10 gears with 285s when the 4x4 conversion happens. Hoping to do a long road trip towing a range rover this summer.
With your raised roof, 265's might put you at the tipping point where you'll no longer be able to hold OD at all times on the highway, especially with a stiff headwind. Unless you have a tuner. Then you'll probably be ok.
How much are you towing? This will almost certainly keep you out of overdrive, and even if it wants to stay in that gear, I'd recommend just locking it out so you don't overheat the trans. Again, situation might be different if you have a tuner. But stock, the programming wants to unlock the torque converter a lot to make steadier HP, rather than keeping it locked for cooler operating temps.
Basically, if it's "hunting" (downshifting to hold speed than upshifting again shortly after speed is recovered) or unlocking the TC frequently, just lock it out.
Under ideal conditions (flats with a tailwind or downhill) you'll be a little better MPG wise. But once you need more HP than it makes in overdrive, than you'll be burning more than now.
Don't forget to compensate your speed for the taller tires. I think your van requires doing the speed-sensor gear swap in the trans to correct it (or adding a pulse converter), or just run a correct factor in your ScanGauge or data-monitor of choice. 265's would be rolling 8% slower than the stock 225s.