I tried my best to bite my tongue and ignore this but you're twisting my arm or was that tail
Putting dual rear tires on SRW F-350 (or F-250/F-150/Ranger/Excursion/Expedition/Explorer) does NOT, repeat
NOT increase the
LEGAL amount the truck can tow. In fact it decreases it, because the extra rim/tire/fenders increase the empty weight of the truck reducing the delta between empty weight and GVWR/GCWR.
A DRW F-350
may have a higher GVWR/GCWR if correctly ordered from Ford. But you can order a 9,900lb GVWR/20k GCWR DRW F-350 that has lower
capability rating than F-250 SRW with 10k GVWR/25.7k GCWR.
A point to ponder: Replacing dual rear wheels on OTR trucks with "Super Singles" increases payload/trailer capacity as they are lighter (by as much as 400lbs/axle). Replacing the DRW on F-350 with SRW of sufficient capacity should do even better as you could get rid of dually fenders.
Swapping cab from a 4x4 payload package #2 Ranger onto a 4x2 frame would technically get you the higher GVWR of the 4wd with the lighter 2wd empty weight, so increasing payload by couple hundred pounds (weight of transfer case/front driveshaft/delta of Dana 35 front axle versus TIB/SLA). But you are dancing on the edge of legal - the VIN of the cab will not match that of the frame.
The aforementioned swap does
NOT change the amount you can tow - the
LEGAL GCWR information is found in owner's manual. Opposition lawyer would be able to rustle one up if you had accidentally misplaced yours.
There are 6 primary items which define strength of gears.
1. Pressure angle: But 90% of industry used the standard, so no difference between automatic and manual there.
2. Diameter of gears: Manual wins big time, enjoying about a 3:1 advantage between M5ODR-1 and Ranger Automatics.
3. Size of teeth: You can make 2 gears of same size with 10 teeth of module 1 or 20 teeth of module 2 or 40 teeth of module 4, etc. The individual teeth just get smaller as the module increases. More, smaller teeth makes for smoother gear interaction, but the smaller teeth are able to transfer less power - Manual wins big time, enjoying about a 3:1 advantage for M5ODR-1 versus Ranger Automatics
4. Thickness of gears: Automatic sun/planet/ring tend to be thicker that manual Advantage about 2:1 for 5rxx for M5ODR-1
5. Number of gears used. Most manuals only use a single counter shaft, while most automatics use their planetaries with multiple planets i.e. 5r44 has 4 planets, while 5r55 has 6. But due to manufacturing tolerances, etc, all the planets do not support equal load. Still advantage Automatic 3.5:1 to 5.5:1 versus Ranger Manual
6. Gear tool material. While I know M5ODR-1 gears are made of 8620, which is 2nd strongest common gear material, I don't know what automatics gears are made of. 9310 is strongest gear material, but it trades strength for wear resistance...good for drag racer, no so good for transmission which needs to last to end of warrantee period. So, probably no difference.
From the raw numbers, the M5ODR1 is fractionally weaker than 5R55 but considerable stronger than 5R44. But there are a couple other components in drivetrain; paraphrasing
@Dirtman: torque converter is more wear resistant than clutch in manual. But automatics are full of bands and clutches and they are very suspect to wear - especially if allowed to get hot. No real difference in the long term strength of either.
So, while I am willing to concede that a 4.0/auto might have slightly higher GCWR from a pure engineering perspective, it would be about the weight difference between the transmissions. And the 3.0 with 3.73 gears should have identical rating. Therefore, there is some other rational for rating automatics higher.
Note: The 2020 trucks use electronics to limit power in lower gears to ensure parts aren't broken. Electronically limiting power is MUCH easier for engineer to do with automatic than manual; so, for new trucks automatics can be rated higher without going to heavier transmission.
At the end of the day, it is what is in the owner's manual that defines LEGAL limit, and Ford rates manuals much lower in the owner's manual.