Possible Wheel/Tire Setup with Speedometer Cal Solution

[ErikSS]

I just put 315/70/17's on my SS. Obviously the Speedo is far from accurate. I've looked at these options, but Amazon wants around $300 for the TruSpeed. Has anyone gotten any of these to work? (I'm aware this is a 2 year old post, but I need the information Now!) lol

[mikekey]

To date, I don't think anyone has.

[06MidnightBlue]

For my $0.02...I use my cell phone, which is mounted using a windshield mount, that has an App called Speedbox. It's free and works great. According to a police friend who used the radar to tag my TB, the app is only off by 1 MPH

[bartonmd]

Erik,

Your SS is newer than 05 by definition, so your speedo (and odo) can be changed in the ecm tune.

Mike

[v7guy]

viewtopic.php?f=14&t=4330

[Jrodgers198426]

I just put 315/70/17's on my SS. Obviously the Speedo is far from accurate. I've looked at these options, but Amazon wants around $300 for the TruSpeed. Has anyone gotten any of these to work? (I'm aware this is a 2 year old post, but I need the information Now!) lol

I'm not sure if you have solved your problem with the speedo calibration, but if by chance you can get ahold of a GM TECH 2 your speedo can be fixed in less than 5 minutes.

[Karo]

So where is the difference between a 02 and a 05 and up Trailblazer?
Isn't it possible to program the correct tire size with a TECH 2 on a 02 Trailblazer and get the correct spedometer values?
Could someone please explain that to me?
Karsten

[v7guy]

the ecm changed in 06. After 06 it became more capable/ tuning friendly. For instance it'll handle having boost and speedo changes. There were changes in the head as well (I want to say the intake and exhaust manifold were revised, but don't hold me to it) hence the higher horsepower rating.

[ErikSS]

So where is the difference between a 02 and a 05 and up Trailblazer?
Isn't it possible to program the correct tire size with a TECH 2 on a 02 Trailblazer and get the correct spedometer values?
Could someone please explain that to me?
Karsten

My understanding is that the 2005 and older Trailblazers are not capable of a simple change in the ECM to change speedometer values. As v7guy just stated, the ecm changed in 2006 making it possible to adust a speedometer for tire size.

[mikekey]

the ecm changed in 06. After 06 it became more capable/ tuning friendly. For instance it'll handle having boost and speedo changes. There were changes in the head as well (I want to say the intake and exhaust manifold were revised, but don't hold me to it) hence the higher horsepower rating.

The heads flow better and had larger valves I believe. This is why a head swap is popular with the low riders on the other site.

[DirtyBacon04]

So are you saying it's possible to swap ECMs but you have to replce the entire head along with it? Forgive my ignorance in this field.

[djthumper]

So are you saying it's possible to swap ECMs but you have to replce the entire head along with it? Forgive my ignorance in this field.

To the best of my knowledge no you cannot swap the ECMs. The ECM on the 06+ also controls the stabiltrak. I am sure there are other things different in the ECM as well.

[v7guy]

You can swap the ecm, it was done on the turbo build on gmtnation.

[djthumper]

You can swap the ecm, it was done on the turbo build on gmtnation.

I think he swapped more then just the ECM along with turning off some of the codes in there.

[v7guy]

So are you saying it's possible to swap ECMs but you have to replce the entire head along with it? Forgive my ignorance in this field.

No, swapping the head is not necessary. I was just commenting, in general, on the differences.

You can swap the ecm, it was done on the turbo build on gmtnation.

I think he swapped more then just the ECM along with turning off some of the codes in there.

Yeah, he ended up swapping over the whole engine harness and ECM and the he rewired everything on the body to match up with the later year ECM/wiring harness. He just punched out the pins in the connectors and moved them to where they would need to be.

In the videos he has up he's still showing a check engine light and it looks like maybe the stabilitrac light.

He also commented that he was emissions exempt, and I doubt he's concerned about stabilitrac (if that's the light showing). I would guess the few things left that are showing lights aren't getting changed. With enough motivation it could be done though.

link to the thread incase there is anyone that isn't aware of it.
http://gmtnation.com/f25/4-2-envoy-turbo-build-4263/



At the end of the day, for nothing more than a speedo fix, it would probably be excessive. I'd just stick with what dirtyanton did and call it a day. His solution works wonderfully.