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Discussion Topic:
speedometer gearing
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unclemark |
12-05-2010 @ 4:11 PM
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Member
Posts: 84
Joined: Dec 2009
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What number gear would be needed for 3.54's and 600x16 tires? This is on a 40-41 1/2 truck. I was told 18 or maybe 17, is this true? I have a 19 which was set up for the 4:11's I had just swapped out. Mark
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deluxe40 |
12-05-2010 @ 4:28 PM
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Member
Posts: 413
Joined: Oct 2009
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The "18" is the correct gear. My car has 6.00x16 tires w/ a 3.54 and the speedometer seems accurate (judging from the "Your Speed is..." signs along the road). Was your speedometer accurate with the 4.11? I thought the 19 was for 3.78 and the 21 was for 4.11.
This message was edited by deluxe40 on 12-5-10 @ 4:29 PM
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unclemark |
12-05-2010 @ 5:01 PM
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Member
Posts: 84
Joined: Dec 2009
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My memory of the number is vague, I noticed it when we were putting the rear end together and back in. At the time i did not realize it's significance. I think it said 19 but I may be wrong. Yes originally it had 4:11s and the speedometer was dead on according to those led radar things set up around town. Now when I pass by I see my speedometer is off with the 3.54s. I will have to pull the floor cover and have a look. thanks.
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supereal |
12-06-2010 @ 7:37 AM
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Senior
Posts: 6819
Joined: Oct 2009
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For future reference, here are the rear end ratios, number of teeth on the ring gear and pinion (often stamped on a web of the housing), and the appropriate speedometer driving gear: 3-54: 39/11 18 3-78: 34/9 19 4-11: 37/9 21 4-44: 40/9 23 4-55: 41/9 23 The gear on the driveshaft is the same for all. It should be noted that the Ford speedometer provides an approximate reading. The above is for the common 600/16 tires and any deviation will result in a change in accuracy.
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37RAGTOPMAN |
12-06-2010 @ 7:44 AM
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Senior
Posts: 1958
Joined: Oct 2009
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were can you find a 18 tooth drive gear for 37 V8 speedometer, ? I need one, any have a extra they want to sell, a good one, thanks 37RAGTOPMAN LET ME KNOW, THANKS,
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deluxe40 |
12-06-2010 @ 9:44 AM
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Member
Posts: 413
Joined: Oct 2009
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unclemark - If you are as lazy as I am, you might try reading the number using a dentist's mirror and a flashlight -- it worked for me.
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supereal |
12-06-2010 @ 11:05 AM
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Senior
Posts: 6819
Joined: Oct 2009
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C&G shows the 18 tooth gear as AA-17271-E for 28-48. (800/266-0470. In general, only the 18 and 19 tooth gears are available. The 19 works with the 3-78 rear, the 3-54 takes the 18. To my knowledge, the housing (turtle) is not reproduced, and some require adapting when gears are swapped.
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unclemark |
12-07-2010 @ 7:39 PM
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Member
Posts: 84
Joined: Dec 2009
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Thanks everyone, very helpful indeed.
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JM |
12-08-2010 @ 6:52 AM
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Senior
Posts: 822
Joined: Oct 2009
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Unclemark, Check with Bratton's Antique Auto Parts on their on line store. They carry the 18 tooth gear and I believe they also have the correct turtle housing as well. http://www.brattons.com/Default.asp?cookiecheck=yes&
JM
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