| norco1030 | -- 12-09-2010 @ 9:59 AM |
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I know the standard differential ratios are 4/11, 3/78 and 3/54. The center section on this Merc is stamped 11-40 which equals 3/64 ratio and the actual gear count is 10-34 whic equals 3.40 ratio. What is the back ground for the non standard ratios? Norm Coffelt, Prineville, Or.
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| supereal | -- 12-09-2010 @ 2:22 PM |
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I've never seen an even rear end ratio. They are deliberately an odd number to allow smoothing of any chipped teeth. That doesn't mean there never wasn't one, of course. Neither of those readings match any common ratios. I'd bet that the actual gear count is 39-11, or 3:78. The stamped numbers on the center section are not reliable, and it is very easy to miscount the teeth on a ring and pinion, as I learned too many years ago. This message was edited by supereal on 12-9-10 @ 2:26 PM
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| Stroker | -- 12-09-2010 @ 3:19 PM |
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The only available ratios for the 32-48 Ford/Merc. axle that I am aware of are: 4.56:1,4.44:1,4.11:1,3.78:1,and 3.54:1 None of these ratios will compute evenly, as Supereal has stated, because all automotive rear axle ratios (even today), employ a "hunting-tooth" principle to spread wear. If you actually have a 3.40:1; 10-34, it would seem to be an aftermarket "one-off". When I count gear teeth, I have found it useful to mark the first tooth with welders soapstone, or chalk, and make sure I don't count that tooth twice. The unreliability of housing stamps that Supereal referred to is due to the fact that many times the original banjo housing has been re-fitted with different gears. If you re-check your tooth count, and come up with a 3.40 ratio, this will make fools of a lot of us! One thing that over a half century of messing with Fords has taught me is that one should never assume that just because all the literature says "this is so"; some strange stuff occasionally slips through.
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| norco1030 | -- 12-10-2010 @ 7:08 AM |
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The center section is stamped 11 40. It is probably the 4/11 ratio and not the tooth count. My mistake on the actual tooth count, it is 9-34 or 3/78 ratio. Thanks for your comment. This message was edited by norco1030 on 12-10-10 @ 7:11 AM
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| TomO | -- 12-10-2010 @ 8:42 AM |
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The 3.63 ratio was a 1941 Mercury only ratio. the banjo would be stamped 11 40. Other ratios for the 41 Mercury are 4.11, 3.78 and 3.54. The speedometer gear would be an 18 tooth and 6.50 x16 tires were used with the 3.63 ratio. I agree that it is very easy to miscount the teeth on the ring and pinion. Tom
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| Stroker | -- 12-10-2010 @ 9:21 AM |
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Tom O: That's really interesting! One of the benefits of this Forum is that for me, it has been quite a learning experience. I wonder what possessed the Mercury division to come up with a 3.63, and then only use it one year? At least they used an 11 tooth pinion, which should have made it a pretty durable assembly. More and more, we are seeing aftermarket asian gearsets that use fewer teeth as a cost compromise, given that hobbing spiral-bevel teeth is time con$uming. Thanks for the rare insight.
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| TomO | -- 12-11-2010 @ 10:39 AM |
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I can only guess why, but they may have thought that the 3.54 ratio was too high for the cars equipped with the 6.50 x 16 tires. The 239 engine was only rated at 95 HP in 1941, in 1942 and later it was rated at 100 HP. Tom
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| Stroker | -- 12-11-2010 @ 11:53 AM |
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Sounds reasonable!
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| 42merc | -- 12-18-2010 @ 3:28 PM |
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3;64 is a real 41 merc & 6 cyl ford ratio. If you were to open it up you would find a one piece driveshaft/pinion, no coupling, unique to these models.
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| 42merc | -- 12-19-2010 @ 3:19 PM |
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I can back up the 6 cyl 3.63 ratio with the green book, part # 1GA-4209. I don't have a Mercury parts book, but I have worked on the 3.63 ratio Merc rear ends in days gone by.
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| supereal | -- 12-22-2010 @ 9:30 AM |
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I'm unaware that Mercury ever put a six in their cars. If you find a 1GA rear in an V8 car, it is likely that the rear end was swapped at some time with a junk yard unit unless there is evidence it was actually used in the Mercs.
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| 42merc | -- 12-22-2010 @ 4:51 PM |
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I guess I wasn't clear with my prior statement.1ga-4209 is a 41 Ford 6 cyl part# for a 3.63 gear set.41 Mercury's also had a 3.63 gear set but I don't have a Mercury parts book to verify a Mercury part#.
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| tbirdhandyman | -- 12-28-2010 @ 6:44 PM |
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The standard ring gear & drive shaft with pinion was a matched set, 3.54 to 1 ratio in the '41 Mercuries. Optional diff. ratios for the '41 Mercury were: 3.78 to 1 (P/N 19A-4209-E) and 3.63 to 1 (P/N 19A-4209-G). The 4.11 to 1 (P/N 48-4209-D) was a '42 - '48 option. When a '41 was equiped with the 3.54 to 1 standard ratio, a smaller diameter (3.18") generator pully (P/N 01A-10130-B was supplied, due to the low rpm's of the engine. My '41 convertible has both the one piece driveshaft/pinion (3.54 to 1) and the small pully. All '41 Mercuries had 6:50X16 tires and used wheel (P/N 19A-1015), which was much heavier that the 11A-1015 used on '41 Fords. In '39 & '40 Mercuries, 6:00X16 tires were standard, and 6:50X16 tires were optional, but used the Ford wheels. The '41 Mercury "19-A" prefix breaks down as follows: 1 = Year - 1941 9 = Engine - 100 HP V-8 (Truck engine) A = Type of vehicle - passenger This data is from "Mercury Chasis Parts Catalogue- 1939 through 1948" Form # 3671-48, dated March, 1948 As someone said: "just because it is in the book, it still could be wrong" Comments, please! Robert E. Tbirdhandyman
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| 42merc | -- 01-03-2011 @ 4:56 PM |
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I agree. I couldn't prove it, but it looks like you did.
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| TomO | -- 01-04-2011 @ 7:17 AM |
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The V-8 Album confirms that all 41 Mercury's had 6.50x16 tires. Tom
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