09 GX470. Planning to install Cornfed 1.5" spacers [front only] and increase tire size from 265/65 to 265/75 all the way around [overlander, not rock crawler]. This should level out the car and give me a small lift. Is there some way to recalibrate the speedo for the bigger tires so the ECU keeps the proper shift points, fueling, etc.? Is this even something I should be worrying about?
I have a working TechStream software program - can it be done with TS?

 

Speedo will definitely be off but shouldn't really affect much other than how much faster/slower the odometer changes. Not sure if it can be adjusted via techstream.. I've always ordered a custom tune so that I could adjust the tire size to correct the Speedo.. Or dealt with it

 

For my 2005 GX 470 one option is to put in a GPS that shows you your exact speed. That will tell you how far off it is at 60 MPH. Then removes the instrument panel by removing the plastic flashing around the instrument panel. Two little plastic screws in the top with Philips. The steering wheel must be all the way down and extended so the key must be on.You also have to pull the wood grained panel on the left by gently prying off and pull the cover out just a little above the ignition.

Once this is removed take out the 2 screws in the top of the plastic screen and gently pull the bottom of the screen out to remove it.

Now the hard part begins. Looking at where your speedometer is setting in the parked mode with key on and knowing how much you need to move it by the GPS you ever so gently remove the dial by slipping a thin pry bar or angled flat screwdriver under the needle and pull it off. Remember it is fragile so don't break it..

Then put it back on adjusting to the GPS finding. Don't put the cover back on until you take it for a spin or two to see if it is correct then put all back together.