Speedometer wrong

So I recently installed a rc 3.5in lift in my 2014 sport did a cmc and now currently spinning 35s. My speedometer is read 65 mph and my actual speed is about 73mph I've been doing alot of reading and found that the hypertech speedometer recalibration dosnt work for my 14. The next thing I've found is the tcase worm gear. And have read alot about it. And have alot of questions. First question. Is this where the truck determines speed. Question 2. If it is how the vehicle determines speed. Can you adjust this with bigger or smaller gears. Question 3. How hard is it to replace? And lastly. What size would I replace it with to get a some what more accurate reading. Thanks for any input.

 

I have this sitting in my garage but haven't had the oomph to take the dash apart yet and cut into wires ...

https://www.tacomaworld.com/threads...-an-easy-alternative-to-the-hypertech.622313/

 

Vehicle speed comes from the rear wheel speed sensors, the ABS module sends it to the instrument cluster, then the cluster sends it out to the PCM and other modules that require it.
The only way to change/calibrate it that I know of is an inline module that modifies the signal.

It is a 0-12v square wave signal.

 

Good time to buy an ultra gauge or something of the sort and use it's speedometer output. It simply scales the trucks internal reading. Plus it gives you a bunch of other OBDII info you really ought to have at hand.

 

Thank you dk_crew, Dm93, and MR5X5 what is the ultra gauge? And what els does it monitor?

 

I'd drive it as is. The math ain't that hard. If the speed limit is 70 just don't go over 65, nobody will write you a ticket for 2-3 over. Even from the factory speedometers are off by that much or more. You'll have a hard time going that fast with 35" tires on there anyway. At slower speeds the difference is even less. Just remember that whatever the speed limit is stay about 5 under and you'll be fine. At speeds of around 35 or less the difference is only 1-3 mph.

 

Why won’t hypertech work on your truck?

Earlier manual trans pulled speed from the t case output which is where the Dakota modifier comes into play (that’s my thread above). I’m pretty sure that sometime around 09 even the manuals started pulling speed from the abs sensor.

I would find the right hypertech part number, buy it on Amazon, try it, and if it doesn’t work, return it because amazon returns are easy.

 

I don't see why it wouldn't work either if it works on earlier models, the signal is the same it just originates from different locations depending on year model and transmission type.

 

So I will say that hypertech didn’t work for me on my 05 manual trans. I plugged it all up and just didn’t have a working speedometer. That’s what led me to trying the Dakota one. But with OP having a 2014, it should be pulling from abs regardless of transmission. Not saying it’ll work with certainty but it should, and I would be curious to see them try.

 

Interesting, I've never messed with one but as far as I know the signals come in and go out of the cluster (Combination Meter) on the same 2 wires regardless of how the the truck is configured and I'm pretty sure they all use a 0-12v square wave.

 

For all I know, it could have been a faulty hypertech unit and I could be wrong about all of this, I really have no idea.

 

If you end up trying the worm gear route you can read through this if you haven’t already:
https://www.tacomaworld.com/threads/dead-speedo-and-odo.782687/page-2#post-28028744

there’s another thread somewhere I thought I bookmarked but cannot find where a user lists some worm gear #’s. Problem is it probably still won’t be absolutely correct at all speeds. I’m roughly 5mph off at 65-70mph on 37s with whatever worm gear the shop that built my truck used.

Another route is an AEM gps speedo. Used one of those in a prior vehicle and worked nicely.

 

Well to be honest I'm just saying the hypertech won't work because when I put the truck info in on the site. It only shows the 3 react tuners. I even called them and asked if they had one that would work. They said they had nothing to calibrat for my year. My next thought was to just buy a cheap laptop and spend the money on hp tunes. Because allegedly. That can do it.