Quote:
Originally Posted by Jim Nolan
OK all you auto masters I need a input. I installed the Dakota Digital speed correction. The instructions are a bit confusing or they are taking something simple and making it difficult. Correct me if I am wrong but the difference between 3:91 and 3:45 is .46. That means 3:45 is 88% of the speed of the 3:91 gears. So all I have to do is correct at say 60 mph to 52.8mph and I will have the same speed as the original 3:45 gears. Does that make sense or am I over engineering it. I did used to drive my math teachers crazy.
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You have a 13.33% speedometer error regardless of the speed. I don't know the procedures for setting the dip-switches in the DD ERA but I believe the 13.33% should satisfy all of the requirements. Some DD might have a "screw" adjustment procedure I believe. If it's a remote location you can't access easily while moving it could very well be a trial and error adjustment confirming with a GPS.
If it's a dip-switch setting you would use actual speed/displayed speed to arrive at a cal ratio. .8816 or .882. There are various DD instructions on the DD web-page based on the revision of the unit:
http://www.dakotadigital.com/index.c...rod/prd393.htm