Will pinion reset affect GDE program?

R80gseric · **Joined:** Sat Mar 08, 2014 10:11 pm **Posts:** 14

Greetings, I did find a glancing reference to this, however would like your help to be certain.
1. When getting a pinion reset to correct speedometer reading, will the ecu be affected? I don't want a dealership tech to blow the gde echo tune.
2. Do 2005 CRDs need the pinion reset or can we just change the speedo gear like on other tcases? I've read some conflicting info on the differences of our 05s and 06s.

Many hanks in advance, Eric

05 CRD
Eco tune
OME / RL front / 9000# winch
EHM / inline stat
Junkyard EVIC
Cracked oil journal in block / aftermarket warranty swapped
Holding old block for rebuild

papaindigo · **Posted:** Sun Dec 28, 2014 9:08 am

Ask GDE directly.

That said to the extent that I know anything about this I do know that the appropriate dealer or equivalent scan tool can be used to adjust, within limits, for different tire sizes. How much that would help for speedo/odometer readings I do not know nor do I know if the adjustment impacts the ECU; I think it's the BCM but...

flman · **Posted:** Sun Dec 28, 2014 9:53 am

I thought speed is read off the tires, but I only thought this and may be wrong? Reading a pinion sounds so 1980s, then you would have a speedo cable, and mine has a wire to the speedo.

R80gseric · **Joined:** Sat Mar 08, 2014 10:11 pm **Posts:** 14

Thanks Gents. I'll ask Keith directly.

There are lenty of pinion reset posts, but I haven't seen one done with gde going into it (and coming out with it)!

papaindigo · **Posted:** Sun Dec 28, 2014 12:27 pm

The FSM is a bit murky, not unusual, but as nearly as I can tell the speedometer is controlled by the BCM and the pinion factor (a.k.a wheel size) to adjust the speedometer is set electronically (not mechanically) in the BCM using a compatible scan tool.

Just curious but how much off is your speedo. As I recall industry standard is +-5% or +-3mph at 60mph. Varies of course with different tires even of the same nominal size. Mine is pretty much dead on but my son's is a couple of mph off both with "stock" size tires but different brands.

R80gseric · **Joined:** Sat Mar 08, 2014 10:11 pm **Posts:** 14

Papaindigo,

Right now I'm within 1mph at 65mph with 245/70/16. Trouble is, my odometer is 1/10th a mile short at 3 miles; meaning it is showing too many miles driven.

I'm changing to either 245/75 or 235/85, 10 ply, soon. I'd much rather the odo be correct for fuel tracking, but the deviations of speedo, odo, and Evic are all so great that I'm not sure it is worth chasing more than one good try.

So, I'll go up on tire size, see where the data is, and then decide if a pinion reset gamble is worth it. Wish I could just swap a speedo gear like the other tcases!

papaindigo · **Posted:** Sun Dec 28, 2014 3:36 pm

To

many different data sources for essentially the same information. Back in the bad old days the speedo and odometer were both driven off the same cable from the same pinion gear and could be manually calibrated. Today the speedo and odometer apparently get their measurements from 2 different data sources, at least I know those readings can be off by different amounts and in different directions, and who knows where the EVIC gets data.

I have an old, perhaps correct or not, memory that the scan tool can input different tire sizes into the system to correct either the speedo or the odometer or ideally both but what those tire sizes are I do not recall. Adding to the issue even within brand tires of the same nominal size can have different diameters which of course change a bit due to wear.

I just run a GPS test for speed (any decent short stretch will do) and miles (I prefer to average several 25 or so mile runs that are relatively straight and level - 3 miles doesn't tell you much and I can affirmatively state highway mile markers are not that accurate) and then keep track of mpg is an Excel spreadsheet with an actual miles driven correction factor built into the formula.

gmctd · **Posted:** Sun Dec 28, 2014 3:49 pm

1/10thmi every 3mi is only 1mi/30miles - that could be tire pressure - not sure variation in tire diameter input is gonna change results very appreciably, but I'm no rocket scientist, so am easily fooled

ATXKJ · **Posted:** Mon Dec 29, 2014 5:25 pm

pretty sure pinion reset is BCM and you have to input revolutions/mile - the tire selections are limited to factory options

the input is off of the rear differential but the computer calculates the display.

I run GPS checks around the speed limits for the speedo

245/75/16 was almost dead on 30-65 and fairly linear.

265/75/16 was close at 30 and 5mph off at 65 and non-linear???

odometer was never close.

CATCRD · **Posted:** Mon Dec 29, 2014 9:38 pm

R80gseric wrote:

Greetings, I did find a glancing reference to this, however would like your help to be certain.
1. When getting a pinion reset to correct speedometer reading, will the ecu be affected? I don't want a dealership tech to blow the gde echo tune.
2. Do 2005 CRDs need the pinion reset or can we just change the speedo gear like on other tcases? I've read some conflicting info on the differences of our 05s and 06s.

Many hanks in advance, Eric

On your 2005 the pinion reset must be done with a DRBIII scan tool. Usually only dealers and well set up shops have them. I used Sir Sam's to do mine. You have to enter revolutions per mile in TWO locations in the scanner menus, one for the speedometer and one for the odometer. You can find rev/mile numbers for your tires on Tirerack.com. It's usually a number around 700 for our general size of tires. I got my speedometer dead on this way, but the odometer not so much.
This won't affect your GDE tune (unless the tech at the dealer takes it upon them self to connect your jeep to the Chrysler Starscan network just to see if you "need any updates" and flash over your tune). In fact, GDE can't change these numbers for you because they are programming the ECM/TCM and not the BCM.

gmctd · **Posted:** Mon Dec 29, 2014 10:09 pm

CATCRD wrote:

R80gseric wrote:

Greetings, I did find a glancing reference to this, however would like your help to be certain.
1. When getting a pinion reset to correct speedometer reading, will the ecu be affected? I don't want a dealership tech to blow the gde echo tune.
2. Do 2005 CRDs need the pinion reset or can we just change the speedo gear like on other tcases? I've read some conflicting info on the differences of our 05s and 06s.
That 'conflicting info' is the '05's require DBIII, as noted, where the '06's require STARSCAN - each dealer scantool is used to program all identical parameters required for each year, incl tire diameter for rpm - rotations per mile
Difference is, the dipsticks at DCJ neglected to program 2005 VIN data into the STARSCAN: there is no selection for the 2005 KJ CRD - I have an '06 ECM for upgrading, and, having done the DCJ in-tank lift pump, the slight rewiring of the rear harness for the '06 ABS system is already been did
Many (t)hanks in advance, Eric

On your 2005 the pinion reset must be done with a DRBIII scan tool. Usually only dealers and well set up shops have them. I used Sir Sam's to do mine. You have to enter revolutions per mile in TWO locations in the scanner menus, one for the speedometer and one for the odometer. You can find rev/mile numbers for your tires on Tirerack.com. It's usually a number around 700 for our general size of tires. I got my speedometer dead on this way, but the odometer not so much.
This won't affect your GDE tune (unless the tech at the dealer takes it upon them self to connect your jeep to the Chrysler Starscan network just to see if you "need any updates" and flash over your tune). In fact, GDE can't change these numbers for you because they are programming the ECM/TCM and not the BCM.

R80gseric · **Joined:** Sat Mar 08, 2014 10:11 pm **Posts:** 14

Gents, thank you for responses. Just after writing my initial question, a city code enforcement officer ran a red light, hit left rear bumper, and spun my wife into pole, damaging rr quarter. Wife not injured. So, I'm going to deal with that (see picture on lost Facebook), then get the new tire setup. Luckily my local yard has some good stuff, including heated leather, rear gate, quarter panel/glass, etc. Maybe we can turn this into overall improvements!

Thanks again for the help.

R80gseric · **Joined:** Sat Mar 08, 2014 10:11 pm **Posts:** 14

Gmctd, CATCRD, and all, thanks for the info on 05 and 06. No WONDER there's so much voodoo out there! The dealers in Portland Maine have ZERO idea about CRD, so I'll re-tire, check data via GPS, and perhaps just keep a log as suggested.

gmctd · **Posted:** Sun Jan 04, 2015 6:24 pm

R80gseric wrote:

Gmctd, CATCRD, and all, thanks for the info on 05 and 06. No WONDER there's so much voodoo out there! The dealers in Portland Maine have ZERO idea about CRD, so I'll re-tire, check data via GPS, and perhaps just keep a log as suggested.

Unfortunately, if too great a change in tire diameter is made, you will need to have the units reprogrammed such that ECM can accurately calculate required injection volume - maybe future ECM's will have built-in GPS for vehicle speed and fuel injection calculations

Will pinion reset affect GDE program?

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