Speedometer Pinion Reset experiences please

[Awww KJ]

The speedo on our 07 4x4 automatic Sport has read high since we bought it. Not terribly, but definitely higher than any other reference point.

It just got its third set of tires which are 235/70, so slightly smaller. I really want the speedo "accurate" and not "no more than 5mph over" accurate.

How do I convey this to the dealer? Because if I get a SW who can't assure me it's going to be better than "as bad as it was before," then I'll either not bother, or I can do a converter box inline.

So how did your experience go?

And refresh my memory; is there a single VSS off the t-case feeding the PCM which then feeds the speedo? An inline ratio converter like a Dakota Digital SGI-5 would seem to do the trick if so, no? The reason I'm asking is because some vehicles use pickups at rear diff, or axles or whatever.

 

[MTN GTO]

I believe there's a magnetic sensor pick-up in the front diff assembly. To control the speedo for different tire sizes, the adjustment is done through the radio, which acts as an input terminal to your computer. This adjustment will set the wheel/tire RPMs to correct the speed you see on the gage. I don't know the keystrokes for performing the operation, it's something done at the dealerships, as far as I know. I never bothered with the adjustment myself.....but if a cop were to stop me for a few MPH over the limit, I'd say he's having a slow day.

 

[Cardhu]

You can always lift and put on 245 75 16. fixed my issues. Was about 10 km/h off at 110 at stock sizes.

The speed goes off one of the wheel speed sensors not off the diff.

 

[u2slow]

You can always lift and put on 245 75 16. fixed my issues. Was about 10 km/h off at 110 at stock sizes.

Same here. Adding the bigger tires made my speedo more accurate.

The speed goes off one of the wheel speed sensors not off the diff.

Interesting. Mine has no wheel sensors, yet the speedo still works!

 

[Cardhu]

Same here. Adding the bigger tires made my speedo more accurate.



Interesting. Mine has no wheel sensors, yet the speedo still works!

no idea on difference between 07 and 05 with respect to speedo but mine has all the esp / tcs stuff that yours doesn't. would seem logical that mine would be linked that way.