Rough Country Speedo Calibration Tool Removes OE Speed Limiter

[Transient]

I wasn't sure where to put this.  It's not a problem, but it's a mod with an unintended result.  Just thought I'd share as it could become a cautionary scenario for somebody.

 

In August my tires were due for replacement.  I decided to also upgrade to 35s.  I also chose to make sure the speedometer would be calibrated correctly by using the Rough Country speedometer calibration tool.  To date I've had zero issues with my setup.  The other day I was on the freeway and decided to make a pass.  Everybody already drives 80+.  My truck is a 2020 Trail Boss LT with the 6.2.  I put my foot in it and made my pass.  When I looked at the speedo I noticed it said 100 mph.  I wasn't intending to go that fast, but the 6.2 likes to go quickly.  Anyways, I let off the accelerator and began to slow down.  I completed my pass, moved back into the right lane, and set the cruise back at 80.

 

From past experience I knew my truck was limited to 98mph.  Going 100 was a little bit of a surprise.  I hesitated to make a post here.  Today I was back on the interstate, but noticed it was clear around me.  The 100 mph speedo readout had been stuck on my mind for a few days, so I decided to check to see if it was a glitch in the matrix.  It definitely wasn't.  I reached 106 today before deciding to lay off and slow back down.  The truck felt great, and I'm experienced at faster speeds due to my history of sanctioned racing, but I was concerned for my truck and wasn't sure if the tires could handle those speeds, or even faster, so I slowed it back down to normal traffic speed (even though none was around me).  This is when I decided to write this post.

 

So, I have a few questions.  First off, is the governor actually overridden/removed?  Is something else at play such as an algorithm that works in conjunction with other OE parameters that only modifies the speed limiter, and I haven't actually reached the speed limiter?  Theoretically, if I had access to a track and was able to run the truck out, what do you think would be my new speed limiter with Duratracs in 285/75r18?

Edited February 29 by Transient
Correctimg numerous typos

[GETGONE]

Interesting. I haven't installed the calibrator in my truck yet since I haven't put the lift or 35's on. I have factory 20" wheels and tires so the MPH cutoff is 112 and not 98. I didn't recall reading anything about the calibrator doing anything with the speed limiter. I know the Pulsar can modify the top speed setting, but that is based on tire speed rating in the computer and not to do with changing tire size.

[Transient]

3 hours ago, GETGONE said:

Interesting. I haven't installed the calibrator in my truck yet since I haven't put the lift or 35's on. I have factory 20" wheels and tires so the MPH cutoff is 112 and not 98. I didn't recall reading anything about the calibrator doing anything with the speed limiter. I know the Pulsar can modify the top speed setting, but that is based on tire speed rating in the computer and not to do with changing tire size.

I don't have a Pulsar.  I also don't have a lift or level, nor spacers for the bigger tires.  I will soon, hopefully at the end of March/ early April.  Everything is already sitting in my garage, except the Pulsar.  I don't think I'm getting that. 

[s10dragracer888]

Hey guys, I read in another post on this forum, and know from first hand experience that the 6.2 will push to about 112 before the limiter kicks in from the factory. I’m not sure about the 5.3. Before I owned my current T1, I owned a 2021 LT trail boss and it would easily do 112.

[GreatWhiteMexican]

I have a 2020 Custom Trail Boss with the 5.3L and 6 speed transmission. Mine cuts out at 98MPH.