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GDE tune plus big tires & different gearing

TheSolarWizard

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just an FYI I called and spoke to them today and the gentleman I spoke to advised against getting the ECU/trans tune if you are regeared. I didn’t dig for a reason because he seemed busy but he said “if it was my Jeep I wouldn’t do it”
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DAVECS1

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There are a number of operating systems that do not rescale the transmission output speed when gear and tire size is altered in the configuration. This means the shift schedule, torque converter, lock schedule, and torque demand need scaled to work with different gear and tire, bit of a process and even then it sometimes does not feel right, and needs further tuning.
 

ilovebikes99

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I would really just want to do an engine tune and benefit from the different EGR setup. The trans is totally fine with me.
 

rharr

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There are a number of operating systems that do not rescale the transmission output speed when gear and tire size is altered in the configuration. This means the shift schedule, torque converter, lock schedule, and torque demand need scaled to work with different gear and tire, bit of a process and even then it sometimes does not feel right, and needs further tuning.
Maybe this is over simple, but doesn't adjusting the gear ratio and tire size with a Jscan or tazer essentially provide the scale correction needed? Seems to work on the OEM tune, and isn't a GDE tune just another version of a OEM tune?

So get a tune then flash the tune with the correct gear ratio and tire size?
 

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DAVECS1

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Maybe this is over simple, but doesn't adjusting the gear ratio and tire size with a Jscan or tazer essentially provide the scale correction needed? Seems to work on the OEM tune, and isn't a GDE tune just another version of a OEM tune?

So get a tune then flash the tune with the correct gear ratio and tire size?
It works on some wranglers and Gladiators that way, and in some that link is disconnected, this my hypothesis, why they do not recommend it. I have dealt with this about 5 times over the last 18 months.
 

rharr

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It works on some wranglers and Gladiators that way, and in some that link is disconnected, this my hypothesis, why they do not recommend it. I have dealt with this about 5 times over the last 18 months.
Interesting. Are you managing a firmware log for your work to see if it's a firmware version issue?

I recall reading a WX post where GDE required a ECU with the most current firmware before a flash.
but nothing about if that flash has programable scales.

Time will tell, this stuff is so new and volatile right now, the goal posts keep getting moved.

Hopefully in a few years things will be better sorted.
 

Keith Diesel

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GDE is not tuning vehicles that are heavily modified from factory as we have no means of testing them in our facility. If OEM did not validate an axle ratio, it would cost us a ton of funds to certify with EPA. For low volume, it does not make a good business case. Nothing to do with firmware, everything to do with government. Go Truckers!!
 

DAVECS1

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GDE is not tuning vehicles that are heavily modified from factory as we have no means of testing them in our facility. If OEM did not validate an axle ratio, it would cost us a ton of funds to certify with EPA. For low volume, it does not make a good business case. Nothing to do with firmware, everything to do with government. Go Truckers!!
If the "Firmware" worked correctly, across the board, tires and gears would not be " heavily modified" and there would be nothing you would have to validate. Simply configure the jeep for the size it has and be done with it, all changes should apply. Unfortunately this does not apply across the board and yes I agree it requires a fair bit of time and resource to identiy the effects of changes not factory delivered.

The comment is nothing aimed at GDE, it is an observation I am making purely based on my own observations as a hobbiest who has clearly fallen into the deep end of this endeavor.
 

Keith Diesel

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If the "Firmware" worked correctly, across the board, tires and gears would not be " heavily modified" and there would be nothing you would have to validate. Simply configure the jeep for the size it has and be done with it, all changes should apply. Unfortunately this does not apply across the board and yes I agree it requires a fair bit of time and resource to identiy the effects of changes not factory delivered.

The comment is nothing aimed at GDE, it is an observation I am making purely based on my own observations as a hobbiest who has clearly fallen into the deep end of this endeavor.
Not sure about any firmware issue, the tire size data is in the BCM. The issue lies with the road load at 55mph. With the axle change and tires, the loads increase significantly and the vehicle coastdown is different. This is what needs to be certified with EPA pertaining to the emission cycles as Stellantis never certified it in that configuration.
 

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DAVECS1

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Yes, I understand tire gear and about 120 other configurations are set throught the BCM.

On some jeeps when the gear and tire are set in the BCM it rescales the transmission output speed as I would expect. This rescale then applies to the NVratio during coast down as deceleration is calculated correctly.

On certain jeeps this works great and has allowed me to share what I have done without much work.

On other jeeps I see TOS speeds a factor of 1.X-2x even after the settings are confirmed correct. As you stated this throws of torque demand, fuel cut off, PE, etc.

GDE has a class leading product and you are foing the rightthings to keep it that way.

I wish Stalantis/FCA would show the same rigor, or atleast throw the aftermarket a bone.
 

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Remember how the transmission behavior on my truck was horrendous after the tune? He postulated that it may have been due to my tires. I had 295/70s on it. I can't confirm or deny that's what the issue really was, but we all know that 90% or more of the guys with Jeeps looking for a tune have aftermarket tires. So.........
 

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Remember how the transmission behavior on my truck was horrendous after the tune? He postulated that it may have been due to my tires. I had 295/70s on it. I can't confirm or deny that's what the issue really was, but we all know that 90% or more of the guys with Jeeps looking for a tune have aftermarket tires. So.........
Did you by chance have a tazer or any other programmer stacked to update tire size? I know this isnt recommended, but what would happen?
 

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If the "Firmware" worked correctly, across the board, tires and gears would not be " heavily modified" and there would be nothing you would have to validate. Simply configure the jeep for the size it has and be done with it, all changes should apply. Unfortunately this does not apply across the board and yes I agree it requires a fair bit of time and resource to identiy the effects of changes not factory delivered.

The comment is nothing aimed at GDE, it is an observation I am making purely based on my own observations as a hobbiest who has clearly fallen into the deep end of this endeavor.
Seems to me if you go bigger tires and gearing to bring it back to factory RPM/ speed range, then the GDE trans tune would be perfectly complementary, no?
 
 



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