Re-geared my 2019

[asilverblazer]

 

On 2/6/2026 at 6:18 PM, Luckyfd1 said:

In my case…going from 3.23 - 4.56, could that 4.56 be too much for the truck to handle?

Too much for which part? Simple answer, no, so long as you can correct the electronics so that everything works and you understand the new physics of a faster spinning driveshaft.

 

On 2/6/2026 at 6:18 PM, Luckyfd1 said:

...but at higher speeds the drive shaft RPM was too high...

Was there a specific symptom that you noticed?

 

On 2/6/2026 at 6:18 PM, Luckyfd1 said:

Meaning you can “trick” the ECM/TCM but there’s nothing you can do about the drive shaft spin… what I’m getting at is the tune can’t do anything about the drive shaft RPM it only makes the computer interpret it differently. The truck is now limited to a lower top speed??? 85 is the new 112… ?

All correct, but the computer doesn't specifically monitor or care what the driveshaft RPM is beyond a speed signal so that the truck knows what to put on the speedometer. This RPM, mph, speed signa, etc. is totally outside of an actual MPH/RPM spin physical limit of the mechanical components. 

 

No 'in line tuner' will ever change the physics of a new gear set.

 

The driveshaft, and everything else up stream of the differential, the engine and transmission are turning faster at any given speed than they were before the gear swap. The physical limits of these rotational forces are just that - physical limits. No electronic wizardry will fix that. Again, the internet claims that higher rotational speed of the driveshaft is a potential for failure. I've seen references of give or take around 120mph WITH THE ORIGINAL GEAR SET. The speed (mph) you should be concerned with driveshaft failure is now lower, how much is unknown, because there isn't a specific number that the driveshaft would fail at before. This is all internet rumor with anecdotal reports. 

 

On 2/6/2026 at 6:18 PM, Luckyfd1 said:

this was prior to the last tune that fixed my truck. I was curious why the inline models didn’t work.
 

does that make sense? 

The truck gets signals from wheel speed sensors and vehicle speed sensors (at a minimum). Presumably, the in line tuner corrects one of those so that the speedometer reads correctly. The software might allow a degree of difference between all the speed signals before it says one of these is wrong and starts causing problems. A full tune could correct ALL signals.