63 speedo gear 10mph slow

[Jim R.]

My buddies 63 has a 370 rear and smaller diameter tires than stock if his speedo reads 45 and he is actually doing 55mph would he need a speedo gear with more teeth or less teeth to correct the speedo, I'm not sure but guessing he has the green one in it now, I guess I would need to know that first or would someone know how many teeth to add or subtract for the 10 mph difference. thanks

[Tracy C.]

Re: 63 speedo gear 10mph slow

Smaller tires will make a speedo faster than actual speed. Smaller tires get more rotations per mile than larger ones. More rotations make your car think it is traveling more miles than it is in an hour. The green one is what is needed for a 3:70. I'll bet it is not what is installed. We are talking about a 20% error margin here. Adding more teeth will slow down the speedo, fewer teeth will speed it up.

tc

[Jim R.]

Re: 63 speedo gear 10mph slow

I had the numbers wrong it shows 65 when he is actually doing 55.

[William C.]

Re: 63 speedo gear 10mph slow

Then you need more teeth on the driven grar

[Edward J.]

Re: 63 speedo gear 10mph slow

Jim, There are two different drive gears (Internal) if the transmisson in a Borg Warner. For the 370 ratio the green driven gear is correct. the drive gears work like this, one of them is for 308 to 355 ratio and the other drive gear is 370-456 ratio.

By adding a couple of teeth to the driven gear it should bring you close enough, not a exact science this way each tooth added will add about 5 mph.gear color should be yellow this is 24 teeth verses the green 22 tooth.

[Jim R.]

Re: 63 speedo gear 10mph slow

Thanks everyone ordered the yellow 24 tooth from paragon 9 bucks

[Wayne M.]

Re: 63 speedo gear 10mph slow

Thanks everyone ordered the yellow 24 tooth from paragon 9 bucks

And if the yellow 24 is still a bit off, you can try a black 23 tooth or an orange 25 tooth.



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