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Old 08-18-2020, 02:53 PM   #2
1930-Pickup
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Join Date: Mar 2017
Location: southern California
Posts: 725
Default Re: 3.78 vs 3.54 rear end and speedometer/miles

Quote:
Originally Posted by springerpete View Post
I have to replace ring gear in my roadster. Presently it is stock which I think is 3.78. If I put in a 3.54 gear & pinion, how will this change the mph and odometer reading ? Thanks, Bill
There is roughly 6% difference between those two ratios, so your speedometer/odometer will be off by about 6%.

With the 3.54 gears, your speedo will read about 6% too low.
When your speedo says '50', you would be doing about '53'.

Last edited by 1930-Pickup; 08-18-2020 at 02:59 PM.
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