How many of you guys have used to trip meter/odometer vs. milemarkers or gps distance to calculate your speedometer error? Is this a known accurate method for the TJ? I recall someone saying that this may not be accurate but I would think that it works fine.
My other quandary is that by my calculations, a 31 tooth speedometer gear would be better than a 32 tooth speedometer gear for my TJ (AX 15, 3.55 gears, 31" KM2s). Every single chart I see indicates that a 32 tooth would be right for me. The one assumption that I'm making is that my Jeep currently has a 33 tooth gear since it came with the Sahara package which had 30" tires standard...I could be wrong and will pull the gear tonight to check.
Anyway, I drove a 50 mile stretch of highway between San Antonio and Corpus Christi and my trip meter read 47.4 miles when it should have been 50 miles on the dot; that's just over 5% error and theoretically a 31.284 tooth gear would be perfect (we all know that's impossible). It would seem like a 31 gear would work great, with less then 1% error and an indicated reading of 70.6 mph while doing 70 mph.