[LSMurderado]

So, I am the second owner of my 2006 Colorado and ever since I have owned it the speedometer has been off. WAY off. It starts reading incorrectly as low as 25 mph and gets worse as it goes up. So bad that when the speedometer reaches 100 and the governor kicks on, the truck is only going 80 mph. I was told VSS, so I replaced it to no success, then I was told the stepper motor is bad in the cluster, replace it too, still same problem. Now the speedometer only works when it wants to, but still shuts the truck off at 80. I am tired of being shut off at highway speeds here in the great city of Memphis where everyone is always trying to qualify for a race and I am getting run over. I know a tune can kill the governor and help alleviate the over 80 situation, but it wont help the speedometer being so far off. I am thinking someone down the line did a gear change. Does anyone else have any other thoughts to why it would be doing this? I want this crap fixed ASAP. Thanks for any help, in advance!

 

[LSMurderado]

With HP tuner?

 

[LSMurderado]

Nothing else wrong. However the tire plackard in the door shows all wheels on the truck being 15" options yet my truck came with the 17" wheel on it. Factory size is 225/75r15 (28.28" tall) and I have 235/50r17 on it (26.25" tall). I still think it has to do with the rear end, though. a smaller tire should not throw off a speedometer 20 mph! The truck is a 3.5L/4L60e, rebuilt trans with upgraded parts, CAI, magnaflow HF catalytic converter, gutted manifold, magnaflow muffler, and it has been lowered 3" in the rear using blocks. No CEL or pending codes at this time

 

[LSMurderado]

according to the calculator the speedo should be off 8 mph at 100, not 20. That is what makes me think the original owner put a weird ass rear gear in this thing

 

[LSMurderado]

I am not saying I want to fly around at 100 mph, but when most interstate speed limits are 70 mph and your vehicle shuts down at 81, people are always running up on me, and I look like an anchor in traffic. I only mentioned hp tuners because a friend of mine a few hours away runs HP tuners and has offered to help with it, but it is hard to meet up with him when he is so far away and works 3rd shift. And he wants 200 bucks, and money isn't something I have a lot of laying around. I know that tuning it would most likely solve my problems, as I have been around drag racing and playing with cars all my life. Thanks for all the input guys. I have replaced everything but the cluster so I am planning on getting a full set from US speedo when I can afford it. The girlfriend just lost her job, so things are REALLY tight right now.....

 

[LSMurderado]

I used a GPS speedometer and a scan tool that measured at the VSS how fast the vehicle was going. When the governor hit and shut it down both registered 80-81 mph

 

[LSMurderado]

The only thing I could think was maybe a dad had this for his son and had someone go in and set something in the computer that shut it down at 80? But that still doesn't explain why the discrepancy was in the gauge itself, with separate stepper motors? It has driven me crazy ever since I got this truck!