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05-10-2010, 06:44 AM | #1 |
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speedometer turtle
What is the no. 19 mean on the turtle. gear ratio? Tankes Walt
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05-10-2010, 07:19 AM | #2 |
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Re: speedometer turtle
Walt, I am quite it is the number for 411 ratio wwith 600-16 tires. Kerk
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05-10-2010, 07:26 AM | #3 |
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Re: speedometer turtle
Walt....it refers to the number of gear teeth on the little driven gear inside the turtle. The speedo drive gear (on the driveshaft just below where the turtle sits) will only have 7 teeth. Ford used the same 7 tooth drive gear (B-17285) for all Ford passenger cars thru 1948, Merc cars from 39-40, and pickup trucks thru 1941. For 1941-42 Mercs they show an 8 tooth gear. The 1942 and later pickup trucks had the open drive trans so they have the 21C drive gears which are altogether different.
The 19 tooth driven gear was most common since it was for the 3.78:1 rear end ratio. The driven gears were available in a small handful of tooth counts, depending on rear end ratio and tire size. The 21 tooth driven gear was used with the 4.11:1 rear end. These charts are in the back of the green bible.
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VANPELT SALES LLC Cincinnati, Ohio Office: 513-724-9486 www.vanpeltsales.com www.classictransmission.com Last edited by Mac VP; 05-10-2010 at 07:47 AM. |
05-10-2010, 08:36 AM | #4 |
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Re: speedometer turtle
Walt, Good thing about this site is when you post something wrong like I did someone like Mac corrects it or gives the right info. Sorry about my mis-information . Kerk
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05-10-2010, 10:13 AM | #5 |
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Re: speedometer turtle
Kerk,
It's funny but I didnt really start out to do any correcting. I was simply going to add part numbers to the discussion, but in the process I saw that the 19T gear was the correct one for the 3.78 rear end. Believe me.....I've been wrong before too!
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05-10-2010, 10:21 AM | #6 |
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Re: speedometer turtle
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05-10-2010, 10:44 AM | #7 |
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Re: speedometer turtle
I don't know this for a fact, but reason leads me to believe there must be slight height differences in the turtle housings, to allow gears of different size to mesh properly with the one size fits all drive shaft gear.
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05-10-2010, 11:26 AM | #8 |
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Re: speedometer turtle
I'v seen posts in the past about the need to use different housings for different tooth count.
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05-10-2010, 01:54 PM | #9 | |
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Re: speedometer turtle
Quote:
Someone posted on the Barn quite awhile back that he had set up and machined the 21's to shorten them so they would essentially be an 18. Maybe he will see this and post...
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05-10-2010, 01:58 PM | #10 |
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Re: speedometer turtle
Ford parts books have the tooth count chart for all the turtles giving correct ones for different ratios and tire sizes...in the 17,000 parts section. Corrections are given for a small number of tire variations.
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05-10-2010, 07:14 PM | #11 | |
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Re: speedometer turtle
Quote:
CW |
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05-10-2010, 07:33 PM | #12 |
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Re: speedometer turtle
These turtles and gears frequently turn up on Ebay, you just have to watch for them. They usually go fairly cheaply. Of course when you are needing one they never seem to show up!
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05-10-2010, 07:55 PM | #13 |
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Re: speedometer turtle
Does anyone know how to get them apart if you want to change gears?
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05-10-2010, 08:57 PM | #14 | |
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Re: speedometer turtle
Quote:
It is no big deal once you see how the shaft is retained. The gear just slides on the shaft and is not pressed on. I hope this helps, CW |
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05-11-2010, 01:17 AM | #15 |
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Re: speedometer turtle
Thanks to all for the good info and help in figuring this out.
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