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Speedo driven gear
#1150527 02/16/2016 11:04 PM
Joined: Oct 2011
Posts: 36
Leominster,MA
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bucketlist51
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bucketlist51
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Leominster,MA
I have the sm420 granny gear transmission in my 51 and would like to know if there were different speedo driven gear tooth counts for that transmission. Mine is a 14 count tooth and I saw one for sale on ebay that was a 12 tooth, supposedly for the same transmission.
I am looking to buy one.

Last edited by bucketlist51; 02/16/2016 11:05 PM.
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Re: Speedo driven gear
bucketlist51 #1150533 02/16/2016 11:28 PM
Joined: Jan 2001
Posts: 5,337
Snohomish,WA,USA
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Pre '68 Dave Offline
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Pre '68 Dave
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Depending on tire size and axle ratios several speedo gear ratios were used on SM420s.
The parts book shows 4 tooth drive and 12 tooth driven for 1948-54 with 4.11 diff.

Last edited by Pre '68 Dave; 02/16/2016 11:32 PM.
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Re: Speedo driven gear
bucketlist51 #1150559 02/17/2016 2:06 AM
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DADS50 Offline
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52-53 had 0-90 speedo

Not sure if that will effect your ebay search

DADS50
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Re: Speedo driven gear
Pre '68 Dave #1150752 02/18/2016 3:46 AM
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Leominster,MA
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bucketlist51
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bucketlist51
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Thanks for the info!

Vietnam Vet 1969-70

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Re: Speedo driven gear
bucketlist51 #1152170 02/26/2016 7:15 PM
Joined: Jan 2010
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Mississippi U.S.A.
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I have a 1949 with a 4-speed (SM-420) out of a 1951 3/4 ton and a rear gear with 3:90 ratio. open drive shaft, but I don' see where that matters but I would sure like to know about what I need also. I did not intend to take your post over just seems like a good place to find out what I need. Thanks Steven

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