Speedometer to wheel size
#1
Speedometer to wheel size
Got a 96 2500 automatic. I am going from stock 16" tires to stock, off a 2012, 17" tire, I think my speedometer will be off some. Can any one suggest a speedometer gear that might get me close to an accurate reading?
Thanks
Floyd
Thanks
Floyd
#2
Registered User
It is not the rim size that changes the speedo, but the actual tire size.
Unless you are changing it a lot, say 30 inch stocker to a 35 inch tire, the amount off will be pretty minimal.
Unless you are changing it a lot, say 30 inch stocker to a 35 inch tire, the amount off will be pretty minimal.
#4
Registered User
How much bigger is a stock '12 tire to a stock '96 tire. An inch maybe?
What do the two tires look like next to each other on the floor? Is one a lot taller? I doubt there is much difference.
What do the two tires look like next to each other on the floor? Is one a lot taller? I doubt there is much difference.
#6
Administrator
Just for grins, i went from the stock 245-75-16 to a 235-80-16, gained about 1-1/2" taller, at 60 MPH the change was slightly less than 2 MPH, so indicated 60 is actually 62.
You would have to really get different for it to matter much.
You would have to really get different for it to matter much.
#7
Registered User
Like I said unless it is a big change in tire size it is not worth a speedo gear change.
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#9
Registered User
I have ~31's on my 2nd gen, and the MPH is off by ~7mph,
do I just take it to a tranny shop & have them try different gears, or buy gears & do it myself (in other words, will pulling the speedo gear/cable drain out a ton of tranny fluid out?)
do I just take it to a tranny shop & have them try different gears, or buy gears & do it myself (in other words, will pulling the speedo gear/cable drain out a ton of tranny fluid out?)
#10
Registered User
As I recall these trucks have electronic speed sensors so a gear isn't used anyway.
Look up new vs old tire diameters and see what the difference is.
I also went to 235/85 tires and my speedometer is more accurate on my "95.
Look up new vs old tire diameters and see what the difference is.
I also went to 235/85 tires and my speedometer is more accurate on my "95.
#11
Registered User
On truly electric speedo tcases, the pickup is aimed directly at the output shaft (not tangential as with mechanical) to read the toothed reluctor ring.
I believe later trucks dropped the tcase speedo completely... sharing the ABS signal off the rear axle.
#12
Administrator
On your 2006 it it all programming, dealership should be able to accommodate you or I know some programmers do have the ability to adjust, but which specific models are able to I don't know.
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