I was just wandering about my 46 RE, is it a heavy duty transmision or are others? basically would someone give me an order on how the ram transmisions rate among each other?

 

4 = Four speed
6 = Strength (the higher the stronger)
R = Rear wheel drive (even though it may be a 4x4)
E = Electronic (Other option is hydraulic)

You are most interested in the second number.

 

As jwleonard said,
According to a Chrysler publication, "Fundamentals of Automatic Transmissions":
1st Character - Number of forward gears (3-5)
2nd Character - Duty Rating (0-7)
3rd Character - Drive Type (A=All Wheel, L=Longitudinal, R=Rear Wheel Drive, T=Transverse0
4th Character - Control System (H=Hydraulic, E=Electronic, FE=Fully Electronic)

Of course, in the publication, "Fully Electronic Automatic Transmission Operation and Diagnosis," the first character is refered to as the number of forward speeds (instead of gears).
The 545RFE (a 5-speed automatic transmission), for instance, in this publication, the first "5" is said to represent the number of forward gears, while the "4" represents the number of forward speeds.

There is a 48RE (goes behind the diesels), so, for all intensive purposes, the 2nd character can go up to 9.

Anyways...