1949 Merc diff gears?

The 1949 and some early 1950 cars had the Dana 41 rear axle with the round cover on the back. The most common ratios for those was the 3.91:1 but as was mentioned there were 4.27:1 & 4:55:1. The Merc-O-Matic didn't come out till mid year 1950 so the rear axles were all Dana 44 by that time. The case is different and the carrier diameter was limited on the Dana 41 & some of the Dana 44 stuff crosses over but I'm not sure what will work and what won't. Parts for the Dana 44 are still available with the 19-spline rear axle shafts and there are several diameter carriers & all sorts of ratios that will fit them available. This is the same basic axle used in the F1 pickups and they had 41s & 44s in the same time frame. A person can use the 3.78:1 out of an F1 if they wanted to.

Randy's Ring & Pinion, or whatever he calls it now, is a good source for info and parts for the Dana axles.
 
My '49 came with 4:27 with OD. When I tore the trans out I replaced it with the 3:90 which did come out of a non-OD car. There may have been 3:91’s in OD cars but I never knew of one.

John
 
Flat land cars with manual transmissions all had the 3.91:1 (some had 3.92:1) whether they were standard or overdrive. The 4.27 was specialized for mountainous terrain driving. The 4.55:1 was optional for trailer tugging or the like. When the Merc-O-Matic was introduced, the 3.31:1 and 3.54:1 rear gears were used depending on the customers application but taller gears could also be used but not recommended due to the nature of those first generation Borg Warner automatics.
 
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