GM Speedo Recalibration?

Herbie

Herbie

Adventurist
Hello all. If I recall correctly there are at least a couple of GM techs on the site, so I'm hoping someone can give me the skinny on whether (and how much) a GM dealer/service place can make whatever adjustments are needed to compensate for my recent axle-ratio change (and less-recent tire size change). Speedo was a little off before, but after the gear change it's WAY off, in the other direction.

It seems that Hypertech is the one and only company that makes a "Speedometer Calibrator" for the Astro van (though I suspect that such tools for an S-10 Blazer would also work since Astro users have discovered that 4x4 Blazer functions exist in our ECU). That tool will run me about $230. Would there be a one-time fee to have the dealer make those adjustments directly that's less than that price?

Particulars, if it matters:
2003 Chevrolet Astro
Gears: 3.42->4.10
Tires: P215/70R16 -> P245/70R16 (30")

Thanks much!
 
Generally speaking, the dealer can only select from "available factory options" for your particular vehicle, ie, factory tire sizes and axle ratio's. Most any dealership is going to charge an hour of labor for a reflash, so for another $75 you can own the tool.
 
Thanks all. That answers it.

EDIT: Calibrator ordered. Always happier to be able to DIY plus have a potentially resellable tool...
 
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