I am kinda new to tuning i tried to change tire size to program speedometer and it is still off 5 mph at 50. It has 4.10 gear ratio and now has 285/75/16?
I am kinda new to tuning i tried to change tire size to program speedometer and it is still off 5 mph at 50. It has 4.10 gear ratio and now has 285/75/16?
Anyone?
My 09 is off almost that much from the factory. The speedometer and scanner almost never read the same speed either. Does the scanner read the correct speed?
adjust your vss pulses per mile. Use a gps or some other method to determin actual speed, and make note of your speedo. 65mph(actual speed)/60mph(speedo indicated)=1.083333333 Multiply 1.08 by your current vss pulses per mile to correct. If your vss pulses per mile are under what they should be, speedo will read higher then it should. If they are over what they should be will read lower then it should. Depending on the accuracy of your readings, you may need to do this more then once to get it bang on. Numbers are for example only, plug your real numbers in.
Edit: Just looked at 2007 file, you have to adjust VSS tire revs per distance but done in same manner.
Last edited by mecanicman; 03-02-2011 at 11:38 AM.
Thanks Mecanicman i will give this a try I couldnt find this information anywhere. Bigbrian the speedometer on the scanner reads the exact same as my gps but off by 5 from speedometer.
This post may be worth while reading to see what should be modified. Hope it helps some.
http://www.hptuners.com/forum/showthread.php?t=31636
Roy
2007 GMC 3500HD, Sinlge Rear, ECLB, LBZ, Allison, 4x4
- PCV reroute, EGR blocked, 4" turbo back dual out exhaust, pyro and boost gauges, led upgraded cluster and steering wheel controls
2005 Chev 2500HD CCSB, Duramax, Allison, 4x4,
- LBZ mouthpiece, PCV reroute, EGR blocked, pyro and boost gauges
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