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Discussion Starter #1 (Edited)
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 ?
 

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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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Discussion Starter #3
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.
 

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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.
 

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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.
 

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Discussion Starter #6
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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Discussion Starter #7
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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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.
 

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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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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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