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what should my tack read?


edekalil

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I have a 72/510 that was origanaly an automatic the rest of the car is original except for the tires. They are mounted on some Celica 14" rims from about 1980. I do not think they are any taller than the original tires. What should my tack read about at 70 mph or 50 mph?

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Rim size does not matter, but tire size does. The rear end ratio is also important. Generally the N American 510 automatics/standards/sedan/wagons got a 3.889 rear end  so I'll post the following using the stock tire 5.60 X 13" or 175/70R13 which is 22.65" diameter.

 

RPMs in forth gear at

 

70........... 4,049

60........... 3,471

50........... 2,892

 

If this helps ..... 17.28 MPH for every 1,000 RPMs in 4th gear

 

If your tires are larger diameter (not necessarily rim size) then these numbers will be lower

If you should have a lower numerical differential gear ratio such as a 3.70, then the RPMs would be much lower.

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My speedo is not working at the moment.

 

As long as you have those stock tires that should work.

 

Speedo cables are only $20. I think Rock Auto or NAPA still have them. Almost any '70-'79 car or truck will work. Dash end must be screw on... later were clip on. Trans ends were the same well into the late '80s. Length only matters if too short, (she said) you can always tie too much slack up somewhere. I used a 4x4 trans case speedometer cable for a while on my 620. It came up past the engine around the air filter over the rad and back to the firewall. 

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