What did you do to your NNBS GMT900 Tahoe/Yukon Today?

[Doubeleive]

Im sure.
I have been over it all at least 10 times before i learned about the pulses per mile adjustment.
The thing that stumps me is using the gear/tire tool in HP Tuners and the one in Blue Cat it is still wrong. Never had this problem before.
I'll load the new calibration in the morning and see how that does.

The only thing i can think of is maybe the tone ring has a different count between a 10 and 14 bolt but i have not checked that out.

when you open the vcm editor, does it show the current gearing is 4.10?

 

[SpareParts]

Yes

 

[j91z28d1]

Success!! Mostly.
Before adjusting for the new GR the only difference i really noticed was it seemed to shift a little earlier than normal and the speedo was off about 10 mph.
After adjusting the GR to 4.10 it shifts pretty good and it feels good. Acceleration is WAY better, love it.
Problem now is i can not figure out how to get the speedo to read right. It reads 6 MPH fast comparing to GPS. I have tried the gear/tire wizard in HP Tuners. Does not help.
I'm not sure how to fix that.
Can someone help me out with that?

hp tuners had worked for the speed on my yukon and c6. might have too Google how to use it, I've been a while but I believe I used the gear cal and then put thst number on the box and flash.

it's over on the hptuners forum how do it

edit, you used the difference in speed to spit out the offset number needed. I don't believe you can just type in the gear ratio? I've used it for tire size, not gear change. so mph is what I used.

 

[mikez71]

I've used it for gear change, but small change and maybe my speedo is off and I don't know it..

From 3.08 to 3.42, the only change (other than GR) in factory tunes was:
Vehicle Speed Sensor / Pulse Average... 3.08=10, 3.42=11

But the vss pulse average is all over the place for various tunes..
'08 Silverado2500 w/3.73 is 13
'07 Silverado2500 w/4.10 also 13..
'10 yukon2500 w/3.73 is 11
'10 Silverado2500 w/3.73 is 12
'11 & '12 sierra2500 no vss average field shown..

 

[SpareParts]

I have lowered the pulses per mile from 93,446 to 74,776. See what that does.

 

[Joseph Garcia]

I have lowered the pulses per mile from 93,446 to 74,776. See what that does.

View attachment 482367

When I changed to 4.10 gears, my shop was unable to correct the speedometer reading using HP Tuners. That certainly doesn't mean that it is not possible. I finally got the speedometer corrected, when I received my BlackBear TCM tune.

 

[Joseph Garcia]

Success!! Mostly.
Before adjusting for the new GR the only difference i really noticed was it seemed to shift a little earlier than normal and the speedo was off about 10 mph.
After adjusting the GR to 4.10 it shifts pretty good and it feels good. Acceleration is WAY better, love it.
Problem now is i can not figure out how to get the speedo to read right. It reads 6 MPH fast comparing to GPS. I have tried the gear/tire wizard in HP Tuners. Does not help.
I'm not sure how to fix that.
Can someone help me out with that?

Quite the difference in the acceleration feel with the 4.10 gears. In fact, on the longer runs around town, my foot gets a bit fatigued, just staying OFF the gas pedal.

 

[mikez71]

Interesting, I don't even see the PCM output calibration for the later trucks..
Must be an '07 only thing..

 

[SpareParts]

Black Bear uses EFI Live. I'm sure HP Turners is just as capable to fix the speedo, just need to figure it out.
I think im on the right track after seeing Doubeleive post and what i found on HP Tuners forum.

I have no idea when the PCM output calibration would or would not be shown.

 

[RooTBeeRthe1st]

Im sure.
I have been over it all at least 10 times before i learned about the pulses per mile adjustment.
The thing that stumps me is using the gear/tire tool in HP Tuners and the one in Blue Cat it is still wrong. Never had this problem before.
I'll load the new calibration in the morning and see how that does.

The only thing i can think of is maybe the tone ring has a different count between a 10 and 14 bolt but i have not checked that out.

Interesting, id think if it did the abs system would trip out and throw the light on.
I know mine swapped no problems thankfully.

 

[RooTBeeRthe1st]

Interesting, I don't even see the PCM output calibration for the later trucks..
Must be an '07 only thing..

Oops, I didn't even see he's got an 07, that would change things with the 4spd and all...needing the conversion u joint and such

 

[SpareParts]

6 speed.

 

[RooTBeeRthe1st]

I have lowered the pulses per mile from 93,446 to 74,776. See what that does.

View attachment 482367

Maybe Instead of using wheel speed, change it to VSS and see if that fixes it.

 

[RooTBeeRthe1st]

6 speed.

Reading> me apparently

And all these posts are because I'm on my phone.

Anyway ..coffees almost gone so I need to crawl under the h0e and change the rest O2 sensors...I need to smog it for my registration and literally yesterday CELs came on twice for it... Timing is impeccable

 

[SpareParts]

Being AWD it does not use a VSS. it uses wheel speed.

 

[RooTBeeRthe1st]

Being AWD it does not use a VSS. it uses wheel speed.

Now I'm unintentionally learning...gm does some funny stuff with big differences on the same platform

 

[Doubeleive]

Now I'm unintentionally learning...gm does some funny stuff with big differences on the same platform

2wd use the transmission tail and 4wd/awd read from the transfer case

 

[Doubeleive]

according to google the vss is on track between 630~650
shift points should be updated & fast learn on transmission

 

[mikez71]

Being AWD it does not use a VSS. it uses wheel speed.

Is only the speedo off? (Did your datalog show the correct speed?)
Was it 6mph fast at 30mph actual?

Only thing I have heard about the tire wizard is tire diameter needs to be .5" large for some reason..
But that wouldn't be 6mph difference unless going real fast..

I wonder if wheel speed is calculated from driveshaft speed..
In that case you might change VSS tire revs per dist to 766.30..

 

[Doubeleive]

google says the pulse per mile should be 103,000 or more if still slow speedo
depends on the tire size (31.5")