46RE and 46RH uses the industry standard automatic transmission identification/specification system introduced a decade or so ago. The first number indicates number of forward gear ratios, second indicates (driveline) load capacity, R indicates rear output (driveshaft). As noted previously, H indicates hydraulic managed gear shifting and E indicates electronic managed gears.
Under this system, an A727 is 3xRH, Torqueflite is probably a 35RH and Loadflite probably a 36RH or 37RH.
Yes, both 46RE and 46RH are both actually A518 automatics, just using the new designations.
I use Mopar instead of trying to keep up with the name changes. (Sometimes, I use Mother Mopar and her five sons.)
Mopar corrected the issue with inadequate lock-up clutch material in OEM torque converter way back in the 90's. There is at least one aftermarket torque converter, mostly marketed to rock-crawlers, that's more bullet-proof but everybody should be okay with OEM torque converter. (Be careful with most third-party torque converters ... the less expensive ones use little or no quality control.)
Mopar has had no reason to change the three speed internals since 1962, right up to present day. What's in the A518/46RH/46RE is identical to the internals my daughter has in the 1962 PB A727 for her '59 Savoy restomod project.
The A518/46RH/46RE problems are in the tailcone, where the OD is located. Compare a picture of an A728 to an A518/46RH/46RE. You'll see the midsection, where the three-speed gears are, is identical outwardly. They're also effectively identical internally, at least as far as planetaries, clutches, and bands.
The A727 is effectively bulletproof, on a par with a Dana 70 rear axle. Clutch and bands will wear out, after hundreds of thousands of miles. Anything else is due to neglect or extreme abuse.
I am aware of some issues with valve bodies and electronic solenoids but many of those can be traced to neglect or people who should not be allowed anywhere near tools.
The same applies to the three-speed midsection of A518/46RH/46RE transmissions. The problems, other than neglect and abuse, are entirely in the OD tailcone. (I've seen indications Mopar improved the OD internals in the last 10-20 years but haven't been able to confirm it yet.)
If you turn off the OD on an A518/46RH/46RE, you effectively have an A727. This is precisely what you should do for long or steep(er) inclines, regardless of load. If towing a trailer larger than the ones Home Depot and Lowes sells, you should turn off the OD and leave it off for the duration of the trip. I'm not saying you won't still have a problem, but turning off the OD will drastically reduce the possibility.
The bottom line is the OD in A518/46RH/46RE's was designed for sedans ... and trucks used like sedans. Turn off the OD and you have something suitable for what pickup trucks were meant to do.
In case anybody was wondering ... I've rebuilt two A727, a Ford C3/FMX, and two Ford E4OD transmissions. Would have rebuilt the A518 in my daughter's van if her first ex-husband hadn't been an effing idiot with a seriously inflated opinion of his personal level of knowledge. (He also when through about a pound of marijuana a week and, that I know of, destroyed 6-8 operational vehicles in a span of 3-4 years.)
1970 Explorer Class A on a 1969 Dodge M300 chassis with 318 cu. in. (split year)
1972 Executive Class A on a Dodge M375 chassis with 413 cu. in.
1973 Explorer Class A on a Dodge RM350 (R4) chassis with 318 engine & tranny from 1970 Explorer Class A
