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Duramax Suburban - IFS Rebuild

So this is a one-time thing to register it, or do you have to go through this biannually?

-- A
 
the BAR process is a one time thing.

You can however get sent to the ref for other reasons.
 
After almost getting stuck sideways in the driveway again, I broke down and ordered tires

285 bfg's on American racing 589's I bought recently on Craigslist. We'll see if I can get them mounted up this week. Need to test fit in front, wheels are a little more inset than I'd like, but will have to try them.
 
Ok, so reading into more details, speedo recal seems to be difficult.

What does everyone recommend? I can go somewhere in town, hopefully someone will have a tech 2 that can do it.

208, russel, what's my best bet? Answers have been varied, and i trust you guys.

thanks!
 
Tech 2 can't adjust your speedometer as far as I know. I always use EFI live for that. However, if you do adjust your speedometer, then your speedo cal verification number will no longer match the stock programming. If you have to have the cal verification numbers matching, you'll need to take the truck to the dealership and they will have to call GM corporate and get an engineer to change the speedo cal value. Then you have to download their special custom cal for your particular VIN from TIS2WEB. If GM does it, then when your VIN is looked up, GM's cal ID and verification number will match. I doubt they will do this for you.

You might want to consider getting a second stock PCM to flash with the stock GM programming to put in for referee visits when they might verify calibrations. You'd have to re-learn the anti-theft each time though. Then you can modify the 1st to your hearts content.
 
Russell said:
Tech 2 can't adjust your speedometer as far as I know. I always use EFI live for that. However, if you do adjust your speedometer, then your speedo cal verification number will no longer match the stock programming. If you have to have the cal verification numbers matching, you'll need to take the truck to the dealership and they will have to call GM corporate and get an engineer to change the speedo cal value. Then you have to download their special custom cal for your particular VIN from TIS2WEB. If GM does it, then when your VIN is looked up, GM's cal ID and verification number will match. I doubt they will do this for you.

You might want to consider getting a second stock PCM to flash with the stock GM programming to put in for referee visits when they might verify calibrations. You'd have to re-learn the anti-theft each time though. Then you can modify the 1st to your hearts content.
Click to expand...

I was thinking about the 2nd PCM approach. That being said, I dont think my yearly check will review CVN's, just will verify no codes. Not totally sure though.

After looking at the tire sizes, i'd be going from 30.7 to 32.6" in diameter. May run GPS on it after the swap and see if its off enough to matter. Always one of those mind game things, as speedo's are that accurate to begin with.


Thanks!
 
dhcomp said:
I was thinking about the 2nd PCM approach. That being said, I dont think my yearly check will review CVN's, just will verify no codes. Not totally sure though.

After looking at the tire sizes, i'd be going from 30.7 to 32.6" in diameter. May run GPS on it after the swap and see if its off enough to matter. Always one of those mind game things, as speedo's are that accurate to begin with.


Thanks!
Click to expand...

Darren, it doesn't matter how accurate or inaccurate the speedo is the PCM still goes by what it's being told to make adjustments for certain sensors. Also I have a buddy who does emission testing and he was recently telling me that coming soon to a smog shop near you (all smog shops in California) they will be reading the calibration ID code against the VIN number and if they don't match instant fail it will be.
 
4X4HIGH said:
Darren, it doesn't matter how accurate or inaccurate the speedo is the PCM still goes by what it's being told to make adjustments for certain sensors. Also I have a buddy who does emission testing and he was recently telling me that coming soon to a smog shop near you (all smog shops in California) they will be reading the calibration ID code against the VIN number and if they don't match instant fail it will be.
Click to expand...

I'm just picky about having working speedo's. The one in my 91 is dead on with 33's now, and i want the 03 to be accurate too.

That being said, i've never run GPS on it as it sits now, so who knows how accurate it is. I'll get the tires and figure out what happens next.
 
dhcomp said:
I'm just picky about having working speedo's. The one in my 91 is dead on with 33's now, and i want the 03 to be accurate too.

That being said, i've never run GPS on it as it sits now, so who knows how accurate it is. I'll get the tires and figure out what happens next.
Click to expand...

I wasn't implying to not worry about it not being accurate, what I was saying is that if it's not accurate the PCM is giving false info to other sensors and you could have decreased mileage issues or even drivability issues.

I too am picky about having things work as they should and accurately.
 
4X4HIGH said:
I wasn't implying to not worry about it not being accurate, what I was saying is that if it's not accurate the PCM is giving false info to other sensors and you could have decreased mileage issues or even drivability issues.
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Got it. Yep, that's why i'm trying to get it right. But from what i read, Speedo and PCM read different sensors or something, and have to be programmed independently.

Russell, you have a good source for used ECM's up there?
 
I do not. LBZ stuff is particularly hard to come by up here and commands a stiff premium.

The PCM isn't super concerned about the speed being bang on. It's used for some defuelling and idle calculations to keep the engine running while you are crawling around in traffic or slowing to a stop. Without any indication, you'll have stalling issues and driveability will be hampered.

The PCM gets it's speed input directly from the output shaft of the transfer case. It has a 40 pulse per driveline rotation tone ring and sensor. That sensor is wired directly into the PCM. The PCM performs the signal conversions and outputs a signal to the speedometer, ABS module etc. There are two settings in the PCM related to speed that we might adjust. One is the speedometer pulse per mile output signal. Stock is 2000 pulse per mile which is what your speedometer is expecting for an input. We generally don't touch this setting.

The other is the number of pulses per mile that the driveline turns. This is the one we are interested in adjusting to correct the speedometer reading. There is a calculator in EFILive which will estimate this value based on your tire size and gearing but you usually need to tweak it a bit to get it just right. I personally use a GPS speedometer app on my phone and go for a drive on the fastest stretch of road you can drive on. I speed up to the speed limit according to my phone and note the speed that is displayed by the speedometer. You enter both these values into the EFI live calculator and it'll correct your speedometer to match. I usually have to do this once or twice to get it just right. You'll wind up with a speedometer that is as accurate as the OEM cal would have been.
 
Russell said:
The other is the number of pulses per mile that the driveline turns. This is the one we are interested in adjusting to correct the speedometer reading. There is a calculator in EFILive which will estimate this value based on your tire size and gearing but you usually need to tweak it a bit to get it just right. I personally use a GPS speedometer app on my phone and go for a drive on the fastest stretch of road you can drive on. I speed up to the speed limit according to my phone and note the speed that is displayed by the speedometer. You enter both these values into the EFI live calculator and it'll correct your speedometer to match. I usually have to do this once or twice to get it just right. You'll wind up with a speedometer that is as accurate as the OEM cal would have been.
Click to expand...

And this is the one that will throw off the CVN numbers? There are some used ECM's on ebay for $150ish. Its probably worth the gamble buying another one, but i'll chat with my builder and see what he has to spare.

We spent so long getting my current one right, i'm hesitant to mess with it. Better play with a different one.

Thanks for all the help!
 
Massive snow storm held up my tires and lug nuts. Hopefully they show this week for install next week.

Fingers crossed the offset works.

Anyone know why American eagle says 33" tires are max size called out for these rims? Not worried about it, just hadn't seen that before. Do all rims say that?
 
Got the wheels and tires mounted up. They actually fit perfectly. With this wheel size and backspacing, plus the 2" body lift in the front, the 285's clear lock to lock. Close in rear, and will still trim the air dam, but overall I'm very impressed. Thought rubbing would be worse.

Truck looks just like I've been working towards. Super excited.

Next, extra ECM with custom dual tank tune and speedo correction. Justin, if you read this, pm me your number. Would appreciate your input.

IMG_0417.JPG IMG_0423.JPG IMG_0425.JPG
 
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