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Quick rear axle question


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I know that the stock axle ratio in my 36 is pretty high, that is RPMs are quite high at highway speeds. (somewhere around 4.20:1 IIRC) I disassembled a Ford unit I had as a spare in order to have the axles and brake drums handy if needed. I understand that the Ford parts are a direct bolt in for the 36 Zephyr. Should I replace the whole center section or remove the pinion and transfer it and the two bearings over to my "Banjo"? I counted the teeth and ended up with 10/34 for a 3.4:1 ratio, that would be great for my Zephyr. Is that the correct count for a Ford ring and pinion in 36-37? I'm 90% sure this rear end assembly was in a 37 2 door passenger car. The gears show virtually no wear, and it is centered on the teeth, no chips or galling, no discoloration. This much of a change would be great for highway driving! I don't think that there will be any trouble with pulling power, I've got plenty of torque as is.

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Hey Mike --

Here's what I've learned about this. The ring and pinion gears were always installed as a set since they were matched at the factory (a TWOTZ cover from a couple issues ago shows this), and by now all these parts have worn together. Second, the pinion bearing set up is a little tricky, even for the non-hypoid axles like yours and mine. Because of this, I'd be inclined to replace the whole thing as a set.

Your original axle ratio as 4.33:1, so this would be a significant drop. Hopefully others wil have something to add.

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Mike, you youngsters are so brain-washed in to effortless, silent, 80 MPH Highway cruising, you completely forget how good a V-12 sounds when it is "buzzing" at high RPM's, and the funny part is the V-12's love it. People going in to OD at 28 MPH probally killed more V-12's than any other single thing, that Ford ratio should be 9:34, which translates to standard Ford 3:78 ratio, much too high for a Z, and you risk becoming a "gutless wonder", another term from the dark ages, but as Cece says, change the whole banjo and ring gear, if you are duty-bound to change it

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Well, I suppose I could shell out $3-4K for a Columbia, if I could find one near me so as to not bring displeasure to the purist gods, but in the interim, I drive my car, alot. Mostly on secondary roads at 50-60MPH. Being able to cruise at 65-70 on the expressway would be a huge plus. As far as lugging the engine, I doubt it. Most of the surface streets here are 35-45MPH and they are always moving. 30% lower RPM as normal cruise speed has to save more in wear on the engine and fuel consumption. That much of a change can't be enough to dog it out, (dare I say it? in low gear, I can squawk the tires, without just dumping the clutch, I did it just once, I was curious but would not consider doing it again, too easy to bust an axle) If you want to look at it from a historical perspective, the roads in 36 were not good enough to consistantly drive more than 45-50. I'd suspect that would be the reason for the taller gears from the factory. I've referred to that particular range as the "sweet spot" in the torque curve (Never did a dyno pull with it), but from the seat of the pants, it seems to be the perfect engine speed, lots of pedal for acceleration left, but also at the point that lifting your foot only slows you down well.

Sorry Rolf, I don't like to hear a 72 year old motor screaming at high RPMs like that, I realize that for the most part it's OK, but we have lots of long, straight, flat roads here. Ideal conditions for leggy rear ends. I want to drive to shows and get togethers as much as possible. Having the option of taking the expressway safely opens up many more opportunities to get out there "Zephyring"

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Point taken, and firmly disagreed with, if you only want to go "Zephyring" as you call it, and not enjoy the full experience of the V-12 and it's potential, so be it, but you are sadly selling yourself short prematurely, and forgive me if that is all you want, just an old V-12 racer spouting off-

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Not at all, hell I look to you old timers for help fixing things I bust. Rolf has forgotten more about HV12s than many of us could hope to learn. Before I start tearing into this maybe I could hook up a tach and get some real RPM numbers, or at least figure out what I have in there. By the rest of the car, I'd say it's original, but I just can't see a car with that high a ratio unless it was intended to run in the 50MPH range for long distance runs. The engine just feels so good at that speed, and seems to be really screaming to hold 70. conversley, it doesn't seem to lug in high at 30-35, it pulls really well in high, I generally shift out of first at 10mph or so (pretty much just to get it rolling or to hold on a hill) then out of second at 25-30MPH. It pulls solid without lugging at all. I can start out in second without trouble or having to slip the clutch a lot. There seems to be no reason to not take this car on the expressways, etc. Maybe I'm incorrect, but in my younger days, I experienced hard part failures in a few engines, street and track, it was always from winding them too high, pushing it higher than I should have, not turning them too slow.

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OK Mike, my "vast" experience goes back to driving mostly Fords in the "Old Days", I even had an obsolete Ford parts store in the San Fernando Valley in the '50's and '60's,(see pic, my name was Joe then), and my experience was that the default 3:78 ratio 9-34 rear end gears were fine in a lighter Ford body, and with a few beans in the engine. In my Ford trucks, usually with stock 100 HP 59A flathead V-8's, I always used 4:11, 9-37 gears, with those I could be heavily loaded, and still be agile enough to maneuver in LA traffic, and on the freeway 65/70 MPH was easy, and I tried to never "lug" a flathead, 8 or 12 down, Henry designed them to "buzz" a little, and with a good set of "pipes", they just sound so good at speed, nuff said, but 3:78's are too high for a Z

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If I'm doing math correctly, changing from 4.88 to 3.8 should reduce rpm by less than 400 at 3000 RPM. A 30% overdrive should get you about twice that much. Wouldn't think the ratio change would kill performance. For all the effort involved, I'd think you would be happier and have more flexibility driving with the columbia or some later Ford or aftermarket overdrive.

Rolf is right, you really don't want to lug the engine. With the lower numeric ratio, you'd want to downshift sooner.

Abe

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OK Abe let's go "bench-racing", we have 2 equal cars, power, transmission etc all the same, you have 3:78's in yours, I have 4:11's in mine, we line up at the stoplight, the light turns green, and guess what, this crazy old curmudgeon who lives in the past is way ahead of you at the next corner, and you can take that to the bank, a very noticeable change in the early Ford ratios, believe me

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It works out to 12.7%,(4.33 to 3.78) so at 3000RPM existing ratio, Whatever MPH that is, I'd only have to turn 2619 RPM. Not much difference, but some. Is that small a change going to lug it down and make it a snail? I don't think so. The big kicker is I have the Ford gearset, I don't have the $3-4K to set up a Columbia. (the only game in town for the 36, I don't want to do anything that requires cutting or damaging my existing driveline like a later Borg Warner OD)

Pipes.... grin.gifThat's a good idea, maybe I can find one of those 4" fart cans like the ricerboys run, maybe glue a big red "R" on the dedcklid, get me some 22" wheels...... wink.gif

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I always remember Chad Coombs talking about driving home in 2nd gear cause it ran so smooth..

rear end stock is 4;44-1. I have done over 80 in regular gear and Rolf is right, smooth and really feels like a Lincoln humming along at that speed...but, My it always seems to run best just before it blows up!!! nice to have od.

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Rolf wins for the first 60 ft, maybe even for a 1/4 mile. Definitely more fun to drive also. But the lower numeric ratio will go faster over a mile. For bench racing, maybe the 46-48 OD would fit a 36 if you used the later drive shaft and torque tube as well? I'd hate to do any cutting too.

Abe

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I used to run BW OD transmissions in a lot of my old Fords, the main trouble is the column shift. This '41 Ford Pickup I built in the '80's had Lincoln brakes, a BW OD, and a converted Z distributor, a '40 Ford car column shift was a bolt in for it, I chopped the Ford driveshaft, ran 4:11 gears, and had the best of both worlds, excellent acceleration from a dead stop, and effortless cruising at high speeds, and with the 4:11's, it would even accelerate enough to pass cars, and pull steep hills without shifting out of OD, it was a fun truck, and I love the grilles, and the sound of the hot flathead

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FWIW, I marked and counted the pinion and ring set I have, it's 9/34. The ring gear is acid etched 78 # 4599 I assume that is the Ford part number. I guess it can sit on the shelf for a while, just in case a Columbia turns up. (yeah, right, in my dreams)

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