Speedo gear for 28" tire

[GNRick]

I have gnx size tires...255X50X16. Should that throw my speedo off by 20 mph? Should I contact VDO and see what they say? My transmission has the stock speedometer gears (11 tooth orange and 30 tooth blue). Rear axle is 3.42. Thanks.

 

[GNRick]

Anybody try the Art Carr Speedo Correction Adaptor? http://www.cpttransmission.com/#

 

[SSedan64]

Should work fine, Ratio Adapters were used by the Factory years ago, 70 Chevelle etc..
A little cheaper here:
http://www.transmissioncenter.net/speedometer_calibration_______va.htm#gm ratio adapter
Or click on link here, if link above doesn't work:
http://www.transmissioncenter.net/speedometer_calibration_______va.htm#gm

 

[GNRick]

Thanks SSedan64. I saw that website but somehow missed the ratio adaptors. I think that is where my transmission guy buys his parts from.