So, hear I am with a new engine and rear end gears. How can I figure out how many miles I have on the engine. When I started up the engine, I reset the "trip distance" button.

Right now it reads about 800miles.

So if I take my old gears(2.73) and divide them by the new(3.89) I get:

0.702

This would convert to a 70.2% speedometer error. Correct?

This means that when I'm going 70.2MPH, My speedometer will read 100MPH.


Can I just take my mileage(800miles) and multiply it by .702?

This would give me 561.6 miles? This is the part I'm unsure about. Is that an average miles reading? Any physics or math experts wanted.

 

800*.702 = 561.6 miles. Were you trying to find out if it is broken in yet? Or just generally curious?

 

Yes, but i was thinking that going 500miles at 70mph would differ than going 500mph at 40mph. Just because it is 70.2% off.

 

no, its the same whether your going fast or slow. The difference in speed increases as you go faster, but the percent difference is always the same.

difference in speed = speedo reading - actual speed => changes

%difference in speed = actual speed/speedo reading = .702
take the derivative and get...
%difference in distance= actual dist traveled/odometer reading = .702

solve for actual distance traveled:

actual dist traveled = .702 x odometer reading
so...
actual dist traveled = .702 x 800miles
actual dist traveled = 561.6miles

trust me, this is right.

 

VSS gets used by the ECM.

I would heartily recommend getting the proper speedo gears in there.

Then there will be no math involved.

but yes the math is right

later
Jeremy