3.31 gears at 40,000 lbs gross.

RoyJ wrote:

ShinerBock wrote:
Hence the reason why the fact still stands that taller rear gears put more stress on the trans and driveline gear for gear than a shorter rear gear. Gear for gear, not one 8th and the other in 10th. Gear for gear.

If gear-for-gear was the strict condition, then sure, I'll absolutely agree the 4.30 truck will have lower engine stress, converter stress, transmission internal stress, driveshaft stress, and equal axle torque.

But that's unrealistic. Why shouldn't the 3.31 downshift twice and match rpm-for-rpm? Ford must agree with me somewhat to make the tow ratings so close.

Also, I'm limiting my statement to modern HD pickups only. i.e. vehicles with power similar to a semi, and transmission ratios better than an Allison BR500. If we include Jeeps/ 4runners with barely adequate gearing for stock 32s, and then putting on 37s, that's an entirely difference story.

See my post above, I made it clear my old Ram very much need a re-gear, and that's just to tow a 10k dump trailer. If I tried a 30k trailer I'll need 4Lo just to nudge it! So my statements weren't meant to be a 1 size fits all for all vehicles / situations.

Did you see the OP's video? His 3.31 axle with large tires was in 10th towing a combined 40k. He locked it out of 10th and 9th, unlike many people who just let the computer do the work which will leave it in 9th or 10th. My 2014 Ram 2500 Cummins with a 3.42 rear gear and 34-inch tires will do the same in 6th. It will hold 6th in many scenarios where it should downshift into 5th to put less stress on the trans. I just lockout 6th, but many people like my brother don't and wonder why they have transmission issues.

The computers in these trucks will be more than happy to keep you in the highest gear possible even though it is not the best thing for your transmission. And just because I have enough engine power to tow in 6th or the OP can tow in 10th, doesn't mean that we should especially with taller rear gears.