4:88.1 from 4:10.1 Why not?

Sounds like we have another happy regear

 

Look up Hypertech, they make a simple inline speedo recalibration module that goes right at the gauge cluster and the software is extremely simple to use.

P.S. I saw a few folks mention gears and the tranny etc in relation to the speedo, they have zero interaction on our trucks everything is read from the speed sensors at the wheels. There is a company that makes a conversion kit to eliminate the sensors at the wheels and add a sensor to the t case for around $175.

 

Thanks man.

Double clicking on a hypertech calibrator right now

 

.

 

Tested again this morning.
Just a hair under the 3k RPM line at 70mph

 

Just a warning, it might still be off. I've had one for 2 years now and have yet to find the right combo of info to enter to get it right. I think its a piece of shit because it hasn't worked right yet for me

 

The right combo of info is entering your stock metric tire size and then actually measuring your current tires and entering in inches as the after size. Even if you have " 35's" don't just enter 35" because 99% of 35's are actually 34 1/2's. Mine has worked perfectly for years and I compare it to GPS every time I update it...that's another issue if your 35's start out at 34 1/2 and wear down to 34's you must update it.

 

So I guess manual trannys use a different location for the speed sensors?

 

Yes, manual 4x4's it's in the T-case, auto 4x4's it's in the transmission, up to a certain year and then they only have the 4 wheel speed sensors and don't even have a #5. At least that is my understanding.

 

This info is right

 

So it asks what size tire was stock, I enter 245/75/16. It asks what tire size now, I enter 315/75/16. It asks what gear ratio stock, I enter 4.10. It asks what gear ratio now, I enter 4.88. The questions are easy to answer and my answer are easy to get right. My speedo is off by 7 mph at 70.

 

I think you are putting in too much info, I only have to enter tire sizes I never use the gear blanks because our speedos work strictly off of the speed sensors at the wheels the gear ratio is irrelevant. I think because you are adding the gear info it is throwing it off and again, don't just enter your metric tire size in the new tire size field actually bust out a tape measure and measure the real height of your tire.

Edit - using this method I verify with GPS and it is exact every time

 

Don't suppose there's any chance you plugged it in backwards?
I use a hypertech in line speedo calibrator and my info is dead on.

2011.
5sp
2.7
stock 4.10
now 4.88
stock tire size 245/75R16
current tire size 285/70R17

 

i may have put it in backwards but i fucked with it like 10 different times. Im pretty sure i didnt do anything wrong as im way to detailed to fuck it up even once. Let me try what yall suggested and see if it works. And my trucks vehicle speed sensor is on the tcase

 

This is really good news. I've been on the fence for gears for a long while, as 4.56 need a new carrier and 4.88 seem to be too high in rpms for highway usage. If you're at 2600 with 32's, I'd probably be closer to 2500 with 285's, right? That would make 4.88s pretty much ideal... My 4 banger is just fine driving around town, but I absolutely loathe taking in on the interstate due to living in the dang Appalachin foothills. I basically have to floor it sometimes to maintain speed on big hills. I think I'm going to take the plunge pretty soon.

 

As long as you are auto. Manual transmission are at a higher rpm at cruising speed.
Use the calculator I posted in my first post. It will give you exact numbers.