Bigbolt, Not all 6400 series trucks had 2 spd. rear axles. I've had 2 that didn't. The 2 spd. rear axle was an option. 3100 is 4800lb. gvw, 3600 is 5800lb. gvw.,3800 single rear wheel, is 7000lb. gvw., 3800 dual rear wheel is 8800lb. gvw.,4100 is 14000lb. gvw., 4400 is 14000lb. gvw.,6100 is 16000lb. gvw., 6400 is 16000lb. gvw.,6500 is 16000lb. gvw.. O.K. now for the COE (cabover engine)trucks, special 1 1/2 ton s5100, s5400, & s5700 series trucks are 15000lb. gvw., all 2 ton COE 5100, 5400, & 5700 series are 16000lb. gvw. Hope all this hasn't confused you. GMC's for '47-'54, on the other hand, have even more gvw ratings.
