re-program on new tires??

[HummerHawaii]

Dealer told me that if i change my tire to p315 with stock rims, i will need to re-program the transmission...is this necessary? On what risk do i take??

Mahalos!

[Sewie]

I think he's talking about reprogramming the computer for the larger tire size.

It was mentioned in another thread that you cannot program the H3 BCM for a tire larger than the 285.

The only risk is that your mileage will not be accurate due to the larger tires.

[f5fstop]

Basically, there is no set recalibration for larger tires. GM does not support larger tires than offered due to safety concerns.
Best thing to do is run the vehicle with a GPS to obtain what the speed of the vehicle actually is with the new tires.
This will serve two purposes; one, give you a factor to use for figuring fuel mileage, and two, let you know how much faster you are going than what is displayed on the speedo...helps to prevent tickets.

[ChevyHighPerformance]

There are speedo recalibrators out there that change the frequency output from your VSS (vehicle speed sensor) to what you need. Some also have a switch to accomodate two differnt size tires (i.e., winter or summer). The speedo box connects or splices in the wires going to the VSS (use to be on the tail of the tranny).

[HummBebe]

Originally posted by ChevyHighPerformance:
There are speedo recalibrators out there that change the frequency output from your VSS (vehicle speed sensor) to what you need. Some also have a switch to accomodate two differnt size tires (i.e., winter or summer). The speedo box connects or splices in the wires going to the VSS (use to be on the tail of the tranny).

Please let us know how to find them. My Dealer ws unable to use the GM program, he could not change the tire size to the 315's I'm running now.

Thanks,

[HummerHawaii]

You running p315 now?
does it jerk once a while?
dealer also told me that they had 1 costumer change rims to 24" with 50 series tire and he came up with this kine problem...i dunno im hoping not to get this kind of problem when i get my 315 shoes

[HummBebe]

do you jerk it once a while?

You must think I'm male?

[f5fstop]

Originally posted by ChevyHighPerformance:
There are speedo recalibrators out there that change the frequency output from your VSS (vehicle speed sensor) to what you need. Some also have a switch to accomodate two differnt size tires (i.e., winter or summer). The speedo box connects or splices in the wires going to the VSS (use to be on the tail of the tranny).

Please explain further. The I/P cluster on the H3 is a dumb cluster. It receives all readouts, except five, from the BCM/PCM via class 2 serial data circuits. There is no input to the cluster from the speed sensor. (Those five readouts are left and right turn signal, seat belt, security, and MIL control.)

There may be aftermarket calibrations out there that change tire sizes, but nothing at GM. If you have a 32 inch tire, and upgrade to a 33 inch tire, the dealer can request, at customer expense, a callibration to change the tire size.

The VSS is located in the tail of the transfer case.

Originally posted by HummBebe:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">do you jerk it once a while?

You must think I'm male? </div></BLOCKQUOTE>

fyi - That bunny picture is lacking any organs of any sort.

[HummerHawaii]

Originally posted by HummBebe:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">do you jerk it once a while?

You must think I'm male? </div></BLOCKQUOTE>

when im in mood, i jerk my 'hummer' once in a while...lol

[HummerHawaii]

no, no not my h3. the guy has to go in the dealer to have his trans re-program.

[ChevyHighPerformance]

Originally posted by f5fstop:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by ChevyHighPerformance:
There are speedo recalibrators out there that change the frequency output from your VSS (vehicle speed sensor) to what you need. Some also have a switch to accomodate two differnt size tires (i.e., winter or summer). The speedo box connects or splices in the wires going to the VSS (use to be on the tail of the tranny).

Please explain further. The I/P cluster on the H3 is a dumb cluster. It receives all readouts, except five, from the BCM/PCM via class 2 serial data circuits. There is no input to the cluster from the speed sensor. (Those five readouts are left and right turn signal, seat belt, security, and MIL control.)

There may be aftermarket calibrations out there that change tire sizes, but nothing at GM. If you have a 32 inch tire, and upgrade to a 33 inch tire, the dealer can request, at customer expense, a callibration to change the tire size.

The VSS is located in the tail of the transfer case. </div></BLOCKQUOTE>

The VSS is a reluctor based sensor that produces XX number of pulses per revolution. The output of the VSS looks like a square wave. The speedo recalabrators splice or connect into the VSS wiring (and get power and ground too), measure the VSS frequency, and feed the PCM another frequency scaled from the original. Here is a PCM screen shot of a silverado's speedometer calibration. You can see the the PCM needs tire diamter, final drive gear ratio, VSS pulses per revolution, etc for speedometer calibration.

[ChevyHighPerformance]

Here are a couple products from JC Whitney (http://www.jcwhitney.com/autoparts/S...&searchbtn.y=9) that do this function. However, the H3 is not listed for either product probably because no one asked either manufacturer to put the correct connectors on the ends.

[HummBebe]

My Dad forbids me from shopping JC Whitney, but if these work, do they work on any vehicle?

If so, which do you rec?

Thanks again!!!!

[ChevyHighPerformance]

Originally posted by HummBebe:
My Dad forbids me from shopping JC Whitney, but if these work, do they work on any vehicle?

If so, which do you rec?

Thanks again!!!!

Here are some other ones (from a google search on speedometer recalibrator):

http://www.drivetrain.com/autotransc...alibrator.html

http://www.4wheelerssupply.com/catal...oducts_id/1762

http://fasttoys.net/shop/product_info.php?products_id=1...fd4907c687ad558f5 293

[f5fstop]

Originally posted by ChevyHighPerformance:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by f5fstop:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by ChevyHighPerformance:
There are speedo recalibrators out there that change the frequency output from your VSS (vehicle speed sensor) to what you need. Some also have a switch to accomodate two differnt size tires (i.e., winter or summer). The speedo box connects or splices in the wires going to the VSS (use to be on the tail of the tranny).

Please explain further. The I/P cluster on the H3 is a dumb cluster. It receives all readouts, except five, from the BCM/PCM via class 2 serial data circuits. There is no input to the cluster from the speed sensor. (Those five readouts are left and right turn signal, seat belt, security, and MIL control.)

There may be aftermarket calibrations out there that change tire sizes, but nothing at GM. If you have a 32 inch tire, and upgrade to a 33 inch tire, the dealer can request, at customer expense, a callibration to change the tire size.

The VSS is located in the tail of the transfer case. </div></BLOCKQUOTE>

The VSS is a reluctor based sensor that produces XX number of pulses per revolution. The output of the VSS looks like a square wave. The speedo recalabrators splice or connect into the VSS wiring (and get power and ground too), measure the VSS frequency, and feed the PCM another frequency scaled from the original. Here is a PCM screen shot of a silverado's speedometer calibration. You can see the the PCM needs tire diamter, final drive gear ratio, VSS pulses per revolution, etc for speedometer calibration. </div></BLOCKQUOTE>

Darn Chevy...I know what a Vehicle Speed Sensor is. I was a bit confused on your first posting, thinking you were saying the VSS sends the signal to the cluster.
I would have to look in the parts manual, but I would bet any of the calibrators, used for many GM vehicles, would have connectors that fit.
Do you know anyone who tried one on a vehicle that had stability control? Just curious if it would mess up the stab system since it calculates based upon speed of the vehicle as well as actual wheel speed.
I would assume there is an algorithm that states the speed of the wheels should be at a set range if the vehicle speed is at this range (or something like that). (Sorry if I'm not being too precise, but just left an all day meeting on the H3 cylinder head serviceability issue, and the H3T, and I'm burned out.)

[ChevyHighPerformance]

Originally posted by f5fstop:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by ChevyHighPerformance:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by f5fstop:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by ChevyHighPerformance:
There are speedo recalibrators out there that change the frequency output from your VSS (vehicle speed sensor) to what you need. Some also have a switch to accomodate two differnt size tires (i.e., winter or summer). The speedo box connects or splices in the wires going to the VSS (use to be on the tail of the tranny).

Please explain further. The I/P cluster on the H3 is a dumb cluster. It receives all readouts, except five, from the BCM/PCM via class 2 serial data circuits. There is no input to the cluster from the speed sensor. (Those five readouts are left and right turn signal, seat belt, security, and MIL control.)

There may be aftermarket calibrations out there that change tire sizes, but nothing at GM. If you have a 32 inch tire, and upgrade to a 33 inch tire, the dealer can request, at customer expense, a callibration to change the tire size.

The VSS is located in the tail of the transfer case. </div></BLOCKQUOTE>

The VSS is a reluctor based sensor that produces XX number of pulses per revolution. The output of the VSS looks like a square wave. The speedo recalabrators splice or connect into the VSS wiring (and get power and ground too), measure the VSS frequency, and feed the PCM another frequency scaled from the original. Here is a PCM screen shot of a silverado's speedometer calibration. You can see the the PCM needs tire diamter, final drive gear ratio, VSS pulses per revolution, etc for speedometer calibration. </div></BLOCKQUOTE>

Darn Chevy...I know what a Vehicle Speed Sensor is. I was a bit confused on your first posting, thinking you were saying the VSS sends the signal to the cluster.
I would have to look in the parts manual, but I would bet any of the calibrators, used for many GM vehicles, would have connectors that fit.
Do you know anyone who tried one on a vehicle that had stability control? Just curious if it would mess up the stab system since it calculates based upon speed of the vehicle as well as actual wheel speed.
I would assume there is an algorithm that states the speed of the wheels should be at a set range if the vehicle speed is at this range (or something like that). (Sorry if I'm not being too precise, but just left an all day meeting on the H3 cylinder head serviceability issue, and the H3T, and I'm burned out.) </div></BLOCKQUOTE>

My thought was that if I wasn't clear to you, I probably was unclear to a bunch of people too.

The PCMs I've interfaced with don't do the stability stuff so I'm not sure how the H3 does it, but the stability systems I'm vaguely familiar with use capacitive accelerometers to measure three axis movement. Vehicle speed is a player, I'm not sure if the controlled gets it from the data bus or calculates it directly. Is there a differnt program for the ABS and stablity modules for adventure and non-adventure H3's or do just the PCMS get flashed differently?

The LS1 ABS and traction control used wheel sensors for each wheel (except the without traction control, ABS used one sensor to measure the ring gear speed for the rear tires) and made a differential measurement (this wheel is spinning faster than the rest -> it must be slipping -> apply brakes to that wheel and/or cut back on throttle) or (this wheel is decelerating faster than the rest or stopped -> modulate brake pressure to that wheel).

[GregDiesel]

I'm guessing when Hypertech release the power programmer for the H3 it will have a setting for larger tires/different gears to calibrate the speedo. The one I had for my Vette did that.

[f5fstop]

The H3 uses the EBTCM for traction and stability contol; however, speed inputs via the Class 2 serial data bus are provided, as well as a few other inputs from sensors, and information from the TCCM.
Not sure about the diffferent program between off-road and non-off-road packages. When I have flashed my PCM, I just capture the VIN via the Tech 2, go to TIS and let the system determine the latest calibration required. I'm guessing there has to be a different calibration for tire sizes (maybe), but especially for different torque settings between the different T/cases. The TCCM has different cals.
I guess we can wait for someone to try and if there are no problems, the calibrators work.
I never knew these aftermarket calibrators were out there, then again, I never needed one before. Nice information to know if ever needed.