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Speedo gears
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   Forward Look Technical Discussions -> Transmission and Rear AxleMessage format
 
59 in Calif
Posted 2017-05-21 2:52 PM (#540517)
Subject: Speedo gears


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Posts: 1034
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Location: Hayward, Calif
Hey Guys, I put a 76, 727 T/F in wife's 59 Dodge. The speed reading is way off. Reads about 45MPH and I'm sure I was doing somewhere around 65. On the speedo housing at the trans are some raised numbers, 32-38, 26-31, and another set of numbers partially covered by the hold down plate. This speedo housing looks like it can be turned to 4 different positions. I don't see how this can be turned to a different setting without changing the inside gear also. Any info on this would be appreciated. Thanks, Jerry
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57chizler
Posted 2017-05-21 3:16 PM (#540518 - in reply to #540517)
Subject: RE: Speedo gears



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The numbers on the outside correspond to the pinion gear inside; for example, if the gear inside is a 33-tooth you would clock the housing so that the 32-38 hash mark lines up with the raised dimple on the tail housing. You need to know the axle ratio and the actual diameter of the tire to compute the pinion gear needed;.



(Speedo_adapter-01.jpg)



Attachments
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Attachments Speedo_adapter-01.jpg (78KB - 83 downloads)
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59 in Calif
Posted 2017-05-21 3:58 PM (#540522 - in reply to #540517)
Subject: Re: Speedo gears


Elite Veteran

Posts: 1034
100025
Location: Hayward, Calif
Where would I find a different pinion gear ? Napa was no help. thanks, Jerry
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oldhippie
Posted 2017-05-21 4:17 PM (#540524 - in reply to #540517)
Subject: Re: Speedo gears


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Posts: 118
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fyi...

http://www.mymopar.com/speedometer.htm

http://www.classicindustries.com/shop/mopar/parts/transmission/spee...
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59 in Calif
Posted 2017-05-21 6:19 PM (#540540 - in reply to #540517)
Subject: Re: Speedo gears


Elite Veteran

Posts: 1034
100025
Location: Hayward, Calif
I checked out those 2 websites. Very informative. I found the pinon gear I need according to their chart. Am I safe in assuming that whatever gear I use will match up with the gear on mainshaft inside the tailshaft housing with no adverse affects ?? Thanks, Jerry
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oldhippie
Posted 2017-05-22 12:59 PM (#540599 - in reply to #540517)
Subject: Re: Speedo gears


Veteran

Posts: 118
100
from what i can see, it shouldn't matter. looks like the groove is cut into the output shaft. i'm no expert though...



Edited by oldhippie 2017-05-22 1:03 PM
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57chizler
Posted 2017-05-22 1:24 PM (#540601 - in reply to #540599)
Subject: Re: Speedo gears



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Location: NorCal
The diameter of the pinion changes as the tooth count range changes, so the adapter needs to be clocked accordingly. The pinions are available from several sources, try e-bay or A&A Transmission.

http://www.aandatrans.com/Departments/Chrysler-727-Trans/Speedomete...

Edited by 57chizler 2017-05-22 1:27 PM




(Speedo Pinions.jpg)



Attachments
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Attachments Speedo Pinions.jpg (23KB - 80 downloads)
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59 in Calif
Posted 2017-05-25 7:37 PM (#540912 - in reply to #540517)
Subject: Re: Speedo gears


Elite Veteran

Posts: 1034
100025
Location: Hayward, Calif
I got a speedo gear from Classic Industries, $60 + shipping and installed it. Speedo reading appears to be right on. Will check it later with wife's GPS map thing. Jerry
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