Gear help please

[Roger63]

I just swapped out my open 2.71 carrier to a 3.55 sure grip. I'm running 235 60R15 tires.
Assuming my speedometer was correct before. What would the speed difference be?

 

[dadsbee]

You won't get pulled over for speeding that's for sure.. it's gonna read high and probably 18MPH or so faster at 60MPH actual than what you're really doing. It's going to be off by 31%.

 

[Jcharger]

real MPH = 0.763 * speedo MPH

0.763 = 2.71/3.55

 

[Jcharger]

Just swap out the speedo pinion gear in the transmission. Something like http://www.brewersperformance.com/products.php?cat=277

 

[Jcharger]

Speedo will read fast.

He will be going about 3/4 of the speed on the speedo.

 

[MoparLeo]

http://www.wallaceracing.com/Calculators.htm

 

[dadsbee]

Yah okay.. we're both saying the same thing.. LOL

 

[RemCharger]

Get a speedometer app for your phone and find out exactly how much difference

 

[Roger63]

Just swap out the speedo pinion gear in the transmission. Something like http://www.brewersperformance.com/products.php?cat=277

Yes intend to when I swap the transmission. Just wanted an estimate.

 

[Frank Mopar]

Get the Speed Box app. Works good. It even has “heads up display”

 

[66Satellite47]

I would NOT assume the speedo was correct before the R&P swap given the tire size you have. Very unlikely a 2.71 gear was matched to that size tire. You need to match the speedo gear to the circumference of the tire size you are using.

 

[Demonic]

Or if you have a highway with mile markers - line up with one and go 10 miles. Compare with your odometer and figure from there.

 

[Roger63]

Thanks for all your help folks. It is exactly 18 mph off @ 60 mph.

 

[RemCharger]

 

[dadsbee]

Thanks for all your help folks. It is exactly 18 mph off @ 60 mph.

What do I win???

 

[Roger63]

What do I win???

Yes your the winner I owe you a chicken dinner.