11-21-2023, 03:39 PM | #1 |
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24 Turtle??
My 38 CS has a 4.11 rear end (stamped 9 37). I believe it should have a 21 tooth speedometer gear in the turtle. Speedometer reads significantly below actual MPH.
I believe correct turtle should be stamped 3 37. Mine is stamped 24 (see photo). Is the current 24 turtle mean it has a 24 tooth gear? As always, thank you in advance for your help! Steve Last edited by 38convsedan; 11-21-2023 at 05:35 PM. |
11-21-2023, 03:41 PM | #2 | |
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Re: 24 Turtle??
Quote:
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11-21-2023, 03:49 PM | #3 |
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Re: 24 Turtle??
Yes 24 tooth gear.
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11-21-2023, 03:55 PM | #4 |
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Re: 24 Turtle??
A 24-tooth driven gear is typically for a 4:55 differential.
If you truly have the 4:11, you need the 21-tooth driven gear. As installed at the factory, it will have a "21" cast upon the housing. This is based on the assumption you have 6:00 x 16" tires.
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11-21-2023, 04:04 PM | #5 |
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Re: 24 Turtle??
Kube, yes-6.00 x 16 tires.
Does this 24 tooth turtle explain speedometer inaccuracy?? Are 21 tooth turtles available? Last edited by 38convsedan; 11-21-2023 at 04:13 PM. |
11-21-2023, 04:50 PM | #6 | |
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Re: 24 Turtle??
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Quote:
Here's a hard-to-find chart with the numbered turtles and their usual applications. Coop . |
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11-21-2023, 05:54 PM | #7 |
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Re: 24 Turtle??
Thanks for the chart!
I don’t see a scenario for 24 tooth turtle with 6.00 x 16 tires…. |
11-21-2023, 06:28 PM | #8 | |
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Re: 24 Turtle??
Quote:
That is likely why your speedometer error exists. I only see two instances on the chart where a #24 turtle is used in conjunction with a 16" tire. Both of those are shod with 5.50 X 16 tires and obviously are fitted with a 4.55 rear end. I'm going to guess that those two combinations were likely 1939-1940 V8-60 powered pick-up trucks, as we know that V8-60 powered vehicles use 16 X 3.5" wheels, and those wheels were considered too narrow for 6.00 X 16 tires. 1940 was the last of the V8-60 engines. #21 turtles are among the most-common. There is a third instance on the chart where a 24 turtle is used, but you'll note that the tire size is a 6.50 on a 15" (fifteen-inch) wheel, probably on a 1947 or '48 farm pick-up with a 4.55 rear gear. Coop . |
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11-21-2023, 07:53 PM | #9 |
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Re: 24 Turtle??
Ok…found three on eBay.
Two seem to be oriented differently my current one, with threaded speedometer cable end facing up relative to stamped 21. The third turtle marked 9 3 and 21 is oriented as the current turtle on the car, with threaded cable end facing down relative to stamping. Which to buy?? |
11-21-2023, 09:03 PM | #10 | |
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Re: 24 Turtle??
Quote:
Me? I prefer the best I can get. In this case, the NOS. It is pricey though.
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11-22-2023, 08:00 AM | #11 |
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Re: 24 Turtle??
Yes any of the three.
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11-22-2023, 08:02 AM | #12 |
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Re: 24 Turtle??
Thanks guys!
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