Transfer Case Speed Sensor Reprogramming ? - Chevy and GMC Duramax Diesel Forum
2017-19 GM T-K2 Platform Powertrain Discussion of components that are directly involved in the power production and all that is needed to get and keep the truck moving . Engine , Transmission, Etc.

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post #1 of 10 (permalink) Old 01-12-2020, 09:53 AM Thread Starter
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Transfer Case Speed Sensor Reprogramming ?

Thinking about changing my differential ratio’s to 4:56’s (optimal ratio for 35 inch tires currently installed).

Was told by the dealer this causes issues with the speed sensor in the transfer case ... because 4:56 is not a factory-offered gear ratio (4:10 is max).

Has anyone successfully changed their ring and pinion ratios to 4:56’s or higher in an L5P (2017-2019) without ECM / TCM / speed sensor issues ?

2019 Chevrolet Silverado 3500HD 6.6L Duramax (L5P) Crew Cab 4x4 SRW Standard Box High Country Loaded w/ Rear Entertainment Package, Fabtech 4” Suspension Lift w/ Heavy Duty Tie Rods, 35” Tires on 18x8.5 Vision Valor Wheels, Luverne Grille Guard w/ Parking Sensor Relocation Kit, Rhino Roll Bar (Sport Bar 2.0) w/ 8” Hella Off-Road Lights, Banks Derringer / iDash / Intake / DPF Back Exhaust, Fabtech Stealth Shocks w/ Front Limit Straps, Front & Rear Hellwig Sway Bars, Airlift Air Bags w/ Wireless Air, DuraFlap Mud Guards, S&B MAP Sensor Spacer, Kryptonite Heavy Duty Pitman and Idler Arm, Centramatics

Last edited by UTEngineer; 01-12-2020 at 03:35 PM.
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post #2 of 10 (permalink) Old 01-12-2020, 10:20 AM
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I installed 4.30’s in the rear last week and working on the front this week. The only issue I have is the speedo is off. Working with the tuner to dial it in now.
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2016 2500hd Custom Sport, Z71, LTZ
Leveled with Moto 961's and 295/70\18 Ridge Grapplers,Amp steps, Weathertech mats, Extang Encore,S&B dry,
Wehrli intake bridge and AFE IC piping,Edge Insight cts2, AirDog II 165,SDP resonator delete, Mishimoto pcv catch can, MBRP down pipe,Recon led tail lights and third brake light, Morimoto mini D2S 5.0 projectors w/hid’s, Morimoto 2stroke 2.0 led’s highs and fogs.
Kryptonite uca’s & tie rod sleeves, CCM diff drop,Fox 2.0 reservoirs, steering stabilizer, CalTracs,
Cognito PISK and heavy duty sway bar links, AirLift bags,
Nitro 4.30’s w/Nitro TracRite posi...
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post #3 of 10 (permalink) Old 01-12-2020, 03:58 PM Thread Starter
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Originally Posted by CDmax16 View Post
I installed 4.30’s in the rear last week and working on the front this week. The only issue I have is the speedo is off. Working with the tuner to dial it in now.
Appreciate the response.

My worry ... the L5P does not have “tuning” capability without changing the ECM ($5k+ w/ tunes) ... thanks to GM locking down everything 2017 and newer ... including my 2019.

This could make even a simple ring and pinion gear ratio change a nightmare ... including transmission shift point / gear change issues ... and a dash lit up like a Christmas tree.

I am willing to continue living with the “sluggishness” of 35 inch tires with the stock 3:73 gear ratio if changing ratios comes with those significant issues.

As for the speedometer correction ... I have the Hypertech Speedometer Calibrator Module (Part #730127) ... which works flawlessly ... but it is simply an inline correction module under the dash.

2019 Chevrolet Silverado 3500HD 6.6L Duramax (L5P) Crew Cab 4x4 SRW Standard Box High Country Loaded w/ Rear Entertainment Package, Fabtech 4” Suspension Lift w/ Heavy Duty Tie Rods, 35” Tires on 18x8.5 Vision Valor Wheels, Luverne Grille Guard w/ Parking Sensor Relocation Kit, Rhino Roll Bar (Sport Bar 2.0) w/ 8” Hella Off-Road Lights, Banks Derringer / iDash / Intake / DPF Back Exhaust, Fabtech Stealth Shocks w/ Front Limit Straps, Front & Rear Hellwig Sway Bars, Airlift Air Bags w/ Wireless Air, DuraFlap Mud Guards, S&B MAP Sensor Spacer, Kryptonite Heavy Duty Pitman and Idler Arm, Centramatics
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post #4 of 10 (permalink) Old 01-12-2020, 07:22 PM
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You won’t need to do any tuning as long as you have the speedo calibrator. As for shift points, that’s why you should do the gears, it will shift like it did when it was stock. The gears will also take a lot of strain off of the rest of the drivetrain, your truck will accelerate easier and tow better.

I wished I had done mine sooner. I can’t wait to get them broken in so I can see what it’ll do.

2016 2500hd Custom Sport, Z71, LTZ
Leveled with Moto 961's and 295/70\18 Ridge Grapplers,Amp steps, Weathertech mats, Extang Encore,S&B dry,
Wehrli intake bridge and AFE IC piping,Edge Insight cts2, AirDog II 165,SDP resonator delete, Mishimoto pcv catch can, MBRP down pipe,Recon led tail lights and third brake light, Morimoto mini D2S 5.0 projectors w/hid’s, Morimoto 2stroke 2.0 led’s highs and fogs.
Kryptonite uca’s & tie rod sleeves, CCM diff drop,Fox 2.0 reservoirs, steering stabilizer, CalTracs,
Cognito PISK and heavy duty sway bar links, AirLift bags,
Nitro 4.30’s w/Nitro TracRite posi...
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post #5 of 10 (permalink) Old 01-13-2020, 11:59 AM
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As for the speedometer correction ... I have the Hypertech Speedometer Calibrator Module (Part #730127) ... which works flawlessly ... but it is simply an inline correction module under the dash.[/QUOTE]

don't wanna hijack , but is the hyper tech speedo correction just in the dash or does it plug in the OBD port ? I have amp steps and CTS2 edge already in OBD and don't want more in it, also concerned like everyone, this is the one that does not effect ECM ? The web site does not show all info for 19's last time I looked.

2019 Chevy Dually Door handles/color matched 110 Gal transfer-flow bed tank / 20"AE wheels Mich. 265/60/20 defender tires /husky rear flaps /cargo box/weathertech mats.tinted glass, xpel on forward surfaces, blacked out pillars
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post #6 of 10 (permalink) Old 01-13-2020, 08:08 PM Thread Starter
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Quote:
Originally Posted by carhauler View Post
As for the speedometer correction ... I have the Hypertech Speedometer Calibrator Module (Part #730127) ... which works flawlessly ... but it is simply an inline correction module under the dash.
don't wanna hijack , but is the hyper tech speedo correction just in the dash or does it plug in the OBD port ? I have amp steps and CTS2 edge already in OBD and don't want more in it, also concerned like everyone, this is the one that does not effect ECM ? The web site does not show all info for 19's last time I looked.[/QUOTE]

No connection to the OBD port. Goes in between a factory plug under the dash. Nothing to do with the ECM. Just simply intercepts the signal to the speedometer in the dash. You do have to preprogram it with your Windows PC telling it your tire size and the factory tire size so it can make the correction.
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2019 Chevrolet Silverado 3500HD 6.6L Duramax (L5P) Crew Cab 4x4 SRW Standard Box High Country Loaded w/ Rear Entertainment Package, Fabtech 4” Suspension Lift w/ Heavy Duty Tie Rods, 35” Tires on 18x8.5 Vision Valor Wheels, Luverne Grille Guard w/ Parking Sensor Relocation Kit, Rhino Roll Bar (Sport Bar 2.0) w/ 8” Hella Off-Road Lights, Banks Derringer / iDash / Intake / DPF Back Exhaust, Fabtech Stealth Shocks w/ Front Limit Straps, Front & Rear Hellwig Sway Bars, Airlift Air Bags w/ Wireless Air, DuraFlap Mud Guards, S&B MAP Sensor Spacer, Kryptonite Heavy Duty Pitman and Idler Arm, Centramatics
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post #7 of 10 (permalink) Old 01-13-2020, 08:22 PM Thread Starter
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Quote:
Originally Posted by CDmax16 View Post
You won’t need to do any tuning as long as you have the speedo calibrator. As for shift points, that’s why you should do the gears, it will shift like it did when it was stock. The gears will also take a lot of strain off of the rest of the drivetrain, your truck will accelerate easier and tow better.

I wished I had done mine sooner. I can’t wait to get them broken in so I can see what it’ll do.
Glad to hear nothing needed beyond the ring and pinion changes since I already have the speedometer calibrator.

I agree that getting the truck back to factory design optimized rpm levels is key to drivetrain longevity and improved towing capabilities.

Still amazed how many negative reactions I got when I mention re-gearing my truck for the 35’s.

Had several comments stating it is unnecessary ... and they also claimed they lost minimal acceleration when they upsized their tires.

Must live in denial ... because it definitely slowed my truck down thanks to the rpm loss.

Even lost 1 or 2 miles per gallon on the highway ... which surprised me running a lower RPM.

I understand some of this is due to more rotating mass ... but I can tell the truck actually has to give it more accelerator when it hits a grade because of running the lower RPM’s.
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2019 Chevrolet Silverado 3500HD 6.6L Duramax (L5P) Crew Cab 4x4 SRW Standard Box High Country Loaded w/ Rear Entertainment Package, Fabtech 4” Suspension Lift w/ Heavy Duty Tie Rods, 35” Tires on 18x8.5 Vision Valor Wheels, Luverne Grille Guard w/ Parking Sensor Relocation Kit, Rhino Roll Bar (Sport Bar 2.0) w/ 8” Hella Off-Road Lights, Banks Derringer / iDash / Intake / DPF Back Exhaust, Fabtech Stealth Shocks w/ Front Limit Straps, Front & Rear Hellwig Sway Bars, Airlift Air Bags w/ Wireless Air, DuraFlap Mud Guards, S&B MAP Sensor Spacer, Kryptonite Heavy Duty Pitman and Idler Arm, Centramatics
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post #8 of 10 (permalink) Old 01-13-2020, 09:46 PM
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Quote:
Originally Posted by UTEngineer View Post
Glad to hear nothing needed beyond the ring and pinion changes since I already have the speedometer calibrator.

I agree that getting the truck back to factory design optimized rpm levels is key to drivetrain longevity and improved towing capabilities.

Still amazed how many negative reactions I got when I mention re-gearing my truck for the 35’s.

Had several comments stating it is unnecessary ... and they also claimed they lost minimal acceleration when they upsized their tires.

Must live in denial ... because it definitely slowed my truck down thanks to the rpm loss.

Even lost 1 or 2 miles per gallon on the highway ... which surprised me running a lower RPM.

I understand some of this is due to more rotating mass ... but I can tell the truck actually has to give it more accelerator when it hits a grade because of running the lower RPM’s.
I have never met someone who re-geared a vehicle for larger tires, with an appropriate ratio, that wished they hadn’t.
Those that say you don’t need to, probably have never done it.
UTEngineer likes this.

2016 2500hd Custom Sport, Z71, LTZ
Leveled with Moto 961's and 295/70\18 Ridge Grapplers,Amp steps, Weathertech mats, Extang Encore,S&B dry,
Wehrli intake bridge and AFE IC piping,Edge Insight cts2, AirDog II 165,SDP resonator delete, Mishimoto pcv catch can, MBRP down pipe,Recon led tail lights and third brake light, Morimoto mini D2S 5.0 projectors w/hid’s, Morimoto 2stroke 2.0 led’s highs and fogs.
Kryptonite uca’s & tie rod sleeves, CCM diff drop,Fox 2.0 reservoirs, steering stabilizer, CalTracs,
Cognito PISK and heavy duty sway bar links, AirLift bags,
Nitro 4.30’s w/Nitro TracRite posi...
CDmax16 is offline  
post #9 of 10 (permalink) Old 01-13-2020, 10:34 PM
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Thanks on the speedo calibration deal!! Also it only makes sense to regear to the corrected specs for tires ect, I know that GM is hung on the 3.73s but if the sales force new what the hell they were doing they would sell it with the correct gears for what a guy wants to do with it, the 3.73 I guess is just a catch all.
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2019 Chevy Dually Door handles/color matched 110 Gal transfer-flow bed tank / 20"AE wheels Mich. 265/60/20 defender tires /husky rear flaps /cargo box/weathertech mats.tinted glass, xpel on forward surfaces, blacked out pillars
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post #10 of 10 (permalink) Old 01-16-2020, 01:00 PM
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Quote:
Originally Posted by CDmax16 View Post
Quote:
Originally Posted by UTEngineer View Post
Glad to hear nothing needed beyond the ring and pinion changes since I already have the speedometer calibrator.

I agree that getting the truck back to factory design optimized rpm levels is key to drivetrain longevity and improved towing capabilities.

Still amazed how many negative reactions I got when I mention re-gearing my truck for the 35’s.

Had several comments stating it is unnecessary ... and they also claimed they lost minimal acceleration when they upsized their tires.

Must live in denial ... because it definitely slowed my truck down thanks to the rpm loss.

Even lost 1 or 2 miles per gallon on the highway ... which surprised me running a lower RPM.

I understand some of this is due to more rotating mass ... but I can tell the truck actually has to give it more accelerator when it hits a grade because of running the lower RPM’s.
I have never met someone who re-geared a vehicle for larger tires, with an appropriate ratio, that wished they hadn’t.
Those that say you don’t need to, probably have never done it.
I regraded my 12’ when I did 37” tires, went with motive 4:56... low end was good but top end was horrible. I’m running 37” now my L5P with 3:73 gears and it does just fine.
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