Reply to 1950TMFWD

    1950T had only one rear pinion and ring gear set and only one gear set for the transfer case.  You stated that you have new 13.6x24 front tires and want to install 18.4x38 rear.  The loaded radius (LR) for the 13.6x24 front is 21.6" and 18.4x38 is 31.3", thus 31.3 divided by 21.6 gives us a ratio of 1.449:1.  Assuming that you have the 8/41 front axle and new tires 1.470 is a match, 1.455 is 1% lead, 1.440 is 2% lead and 1.426 is 3% lead.  1.449 is only about 1 1/2% lead.

    LR is the distance between the center of the axle and the surface the tire is sitting on with normal load.  As you can see tire air pressure will effect LR as will tire wear.  If you raise the tire pressure slightly in the front tire you will increase the lead, 2-3% is desirable.  Also the addition of loads on either the front or rear axle like a heavy three point hitch load or perhaps chemical tanks mounted on the front will effect the match and will have to be adjusted with air pressure to get in the match you need.