38 chevy master deluxe. Did some research but can’t find these numbers. Anyone’s help appreciated. One is the casting number and the other is supposed to be the gears? Thanks Sent from my iPhone using H.A.M.B.
Then, remove the spark plugs, jack up one rear wheel and turn it from there. Leaving one rear wheel on the ground, trans in 3rd (high) gear, turning and counting the other whilst a friend counts revolutions of the crank pulley, 2 revolutions of the wheel to one of the crank? (that's because of the differential gears) If you count 8 revolutions of the wheel, and your crank counting bud counts 1, the rear end ratio is 4:1. (You know...'Four-elevens'?) The transmission in high gear is straight thru. 1:1. Simple arithmetic, really. "Elementary".
Should be 3.73 or 4.22 ratio, depending if it's Master or Master Deluxe. Taxis got a 4.11 ratio. But that's for US cars, we're not sure if it's Canadian or US yet.
Jack one wheel up, put transmission in high gear, turn the wheel 10 revolutions, have someone count how many time the input shaft turns. Divide that my 2, move your decimal one point, that’s your ratio! I think, it’s been a while since if done it. There are other methods. Bones
...and far easier to understand.. Jack up just one rear wheel, put a mark on the tire and floor at the bottom..Now put a mark on one spline of the trans input shaft' Now have a helper slowly rotate the tire exactly 2 turns while you count the turns on the input shaft. If the shaft turns 3-3/4 turns, that is your 3.73. If it turns a tick over 4, then there is your 4.11
I used the method I stated, which is very close to what you do, just times ten to get a more accurate measure. I used it in salvage yards years ago, to harvest rear ends. With out going Xs ten it’s hard to tell if it’s a 3:50 or a 3:42 etc. He may have trouble proving wether it’s a 4:11 or a 4:22 with out going x10, but if it comes out 3:73 , he should be able to tell. Bones
You need to turn one wheel 2 turns (or 20 turns if you want to count 10 turns of the driveshaft), because of the differential. One wheel going two turns, is the same as two wheels turning one turn each.
It’s been many years since I haunted the salvage yards and crawled under cars to determine the ratio. Even back them I would have to remind myself how to do it. I think my description is how I did it. But ratios always kinda confused me. It you are gearing down... say with a 4:11 rear end obviously you can gear down as far as you want. Just for example, you multiply the ratios in the transmission x the ratio of a transfer case x the ratio of the rear end. On some 4x4s the get to 128 to 1 and I guess there is no limit. You could have a 1280 to 1 theoretically. Now with over drive the ratio goes to a fraction, that is like some overdrives are .75 to 1. So..... if you continue to “ increase” your overdrive..... it appears to have a limit as to how far you can go! Ie: .75 to 1, .50 to 1, .25 to 1..... am I going to run out of numbers before I run out of gears? I guess there could be a ratio of .01 to 1. Would that be the opposite of 100 to 1, if you turned it backwards? Let’s just hope there is a tag left on the rear end! Bones
Bones, your thinking way too hard about this. LOL! He was only worried about the rear end gear.... When you add in trans gears and transfer case gears, you get way in front of the rear end gears. Gene
I hear you! Lol.. I was good in math in school, but for some reason ratios always tripped me up. Seems like 1/2 the time I was getting them backwards! I’ll chill out and have a Miller lite... you know most beers have more calories than Miller Lite by 2 to 1. Bones
This was a Ford axle, but in your case the input shaft of the trans will tell you what you need to know. As stated use top gear.
Those hillbilly turn the axle and count deals aren't always accurate even though they have been passed around for the past 60 years I know of. Why not just pop the rear cover off and count the teeth and be done with it and actually know what you have without guessing. You could have done that in the time it took to read all the suggestions.
I think the A means 3.55. Turned the wheel 1 rotation, transmission in 3rd. Trans input shaft turned 3.55 revolution. Rare one. No need to take cover off
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