Hi guys, kinda new here sooo I thought I would start out the right way by showing how little I know, (but I'm willing to learn). I have a 42 / 47 Ford pickup rear end, I think?? I'm trying to figure out the gear ratio. I have checked all over and the only numbers I can find are on the pinion support part of the rear, the numbers I see are a 31 on one side and a 1 on the opposite side. Does anyone have a clue on what these numbers stand for? I'm trying to keep from tearing it down. Its a good clean unit. My Grandson and I are planning on building a Flathead powered HA/GR rail.... you all don't need to worry yet at my pace it will be 2010 before I get it ready to run .. Any information would be appreciated and Thanks JerryE
I would probably be to your advantage to go to the NEW TO THE HAMB and post an intro,,,just to let everybody know a little about yourself,,,HRP
Welcome to the board,,,, if the rear end is a posi unit (not sure if they had them then) you can get a rough idea by turning an axle one full revolution and count how many times the pinion goes around....Example: if the pinion goes around 3.5 times the ratio will be approx a 350:1, a little over 4 turns approx 410:1 and ect....if it's a non posi have someone turn the opposite axle the same time you turn your end in the same direction and do the same math....Not an exact science but it will give you an approx ratio...
yep, that's a 42-48 ford pickup rear. I can never remember the exact ratio's on those but I know they were at least 3.78/1 should be one of the following I think 3.78 4.11 4.4x
42-47 I was told that there were 3 ratios in the banjo, 3.54, 3.78 and 4.11. It really shouldn't have "posi" so have someone hold one axle still, or lock it somehow. Turn the other side 2 turns. Count the number of turns of the pinion. You don't have to be exact on the counts for the pinion ie 3.78, if you get roughly 3 and 3/4 turns you will know the ratio.
If it is a 42-47 Ford pickup banjo rear end, it is open drive. The ratio numbers are stamped underneath and indicate the number of teeth on ring and pinion gears so look closer. Sometimes they are hard to see. NO such thing as posi on early Ford banjos.
I pulled this off another thread, as stated above most are stamped on the bottom of banjo by the pinion. 3.54 11/39 3.78 9/34 4.11 9/37 4.33 9/39 4.44 9/40 4.55 9/41
Of the possible ratios, 3.54 would be very rare, 3.78 common, 4.11 fairly common. Just turn it and see if four turns of the pinion turns the axle (both ends free) a bit more than 1 turn (3,78) or a bit less for 4.11.
Bruce has it right. 99.9% chance that it's 3.78 or 4.11. I have never seen or heard of an actual finding of a 3.54 open rear. I HAVE however found a 4.44 half ton rear before. the little four banger motor used it. THAT is very rare to find.
HeyJerry, If you're planning on building an HA/GR, find the HA/GR forum area of this site. It's under the HAMB Drags section.
Thank you all, I'll go out and look closer to see if there are more numbers. I would like to keep from taking it apart but if I have to I will, just to see what ratio & shape its in.. I was told it has new brakes. I hate removing those rear hubs its been about 50 years since I work on one...
Just rotate it as above--no need to take it apart. There's no need for exact observation, either, because you are just deducing which of the possible numbers it is. It's either gonna come through as a bit more or a bit less than 4...only if you get a deviation from this general area do you need to look closely.
Trust Bruce on this if you cannot find the numbers on the bottom. I am used to doing the spin check as the junk I get usually is newer and has has the tags missing (I am learning a lot with the '46 Ford truck that I am doing and it is my understanding that Bruce has lots of really good practical experience Since I always spin the axle, I just did the math to see what Bruce means by a bit less or more (Sorry Bruce, I hang with a bunch of MN fishermen and sometimes I have to see it to believe it). As he said, if both axles spin freely and you look at one as the face of a clock, the 4.11s will be about 1.5 min before your mark and the 3.78 will be 3.5 min after your mark, so he really means just a little bit. So if it looks like it is 5 min or more either direction from the mark, it would likely be one of the rare ratios. Again if one of the axles doesn't reliably spin freely, just lock that one. The free axle will spin roughly twice though and you would be about 3 min before the mark or 7 min after. As 31Rodder suggested I am going to dig mine out of the snowbank tonight to see if the number is stamped on it (I am sure it is, but I just have to check now). Mine counted out to a 3.78, I was happy about that. Edit - I just checked mine, didn't find any numbers stamped on the bottom, but there is a lot of gunk there that I couldn't easily clean (I don't want to clean it up too much as it needs to stay outside for the rest of the winter).
Rev Kev is right about hard to find. I have at least one of every ratio already mentioned, and a 3.63 that I learned is from a 41 Ford six cylinder. Anybody else have one?
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