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Speedo gear '60 Six

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cnagorka View Drop Down
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    Posted: Dec/04/2022 at 9:00pm
Hey all:

I have a '60 Six w/auto trans and the speedo reads considerably too high (checked w/GPS unit). Indicated 70 mph is about 64 by the GPS. I thought it was being caused by 70 series tires in place of the correct 75 series, but I replaced them and it made no practical difference. There's no mention of the speedo gear in the TSM that I can find. I know the speedo isn't going to be perfectly accurate, but this seems like a pretty considerable error, and it's consistent. Any tips for replacing the gear in the transmission with one for a more accurate reading (like, a different number of teeth for the different rear axle ratios available)?

TIA!

CN
1961 Ambassador Custom, 1967 Ambassador 990, 1960 Rambler Six Super, '65 American 440
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FSJunkie View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote FSJunkie Quote  Post ReplyReply Direct Link To This Post Posted: Dec/05/2022 at 2:00am
The original tires were not 75 series, they were 90 series. Even your 75 series tires will be too short unless you make them a lot wider than the original tires. So wide that the rims or the rest of your suspension might not like it.

5 mph isn't too bad. Error within 3 mph is about all these speedometers did when they were new, according to road tests of the time. 

Increasing the tooth count on the speedometer driven gear by one or two teeth should do it. 
1955 Packard
1966 Marlin
1972 Wagoneer
1973 Ambassador
1977 Hornet
1982 Concord D/L
1984 Eagle Limited
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cnagorka View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote cnagorka Quote  Post ReplyReply Direct Link To This Post Posted: Dec/05/2022 at 4:19am
90 series? I didn't know there was such a thing. Those would have been some really tall, skinny tires. Anyway yes the TSM give a range of speeds for a given rpm of the speedo cable, but this is outside of that range. It's too bad the TSM doesn't give the tooth numbers for the different gears, I guess I'd have to pull mine out and go from there.
1961 Ambassador Custom, 1967 Ambassador 990, 1960 Rambler Six Super, '65 American 440
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1948kaiser View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 1948kaiser Quote  Post ReplyReply Direct Link To This Post Posted: Dec/05/2022 at 5:20am
the parts books do.
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