CTS-V Speedos issue

[Mike_Levy]

Since we managed to crap the other thread, lets try again.

To rehash, CTS-V has different readings for the analog and digital speedo.

Found a possible issue. The rear axle ratio is wrong. When I go into the rear axle section of the Modify menu, it shows a 3.22. The automatic Vs have a 3.23, manuals 3.73. I would think that would mess up both speedos though?

[mikel]

no, thats not the issue.

have you checked this with the stock tune installed? I can't imagine it has anything to do with the tune.

[Mike_Levy]

Didn't say "the" issue, just "a" issue.

Anyway, with the stock tune, they're still off. And neither one of them agrees with the roadside speed traps! The speedos read about 3 (digital) and 5mph (analog) slower then the signs that tell you how fast you're going. That I could see as possibly a rear axle ratio error, if I had a tune installed. Unfortunately, it was coming back from the dealer and I had no tune installed.

All signs point to a GM issue. Still don't know whats right, whats wrong, whats what.

[leeindy]

What does the GPS say? 3.22 vs 3.23 really isn't enough difference to notice around town but could be more pronounced at highway speeds. A half in larger tire size change my reading at highway speeds about 4-5 mph

[Mike_Levy]

I have no idea how to check the GPS speed on this car. The Navi system is way more confusing then the Chrysler MyGig and the Pioneer AVIC-D3 I used to have. I do have an app on my iPhone that reads it though, so I'll have to check it.

[leeindy]

Yeah the app on my iPhone is exactly the same as the garmin and the tom tom I have. Gps will tell you which one is closer to being right