Speedometer Forscan Fix for 37 Inch Tires

[Tylermckee]

I followed OP's instructions exactly on my 22 lariat with 37" toyos and speedo is dead on, I haven't noticed anything abnormal with shifting

 

[Melwinn]

On my 2022, I was able to correct the speedo using the 2770 value without dash lights/error codes for 37x12.5x20’s. It’s dead accurate when comparing multiple different gps speed apps. Did the PCM/TCM relearn after changing the value, didn’t touch axle ratio either. Weird because my truck speedo was 2mph fast from the factory so that helped close the gap when going to 37’s.

Not sure why its so different for everyone but this was the case for me as well. Guess we are lucky!

When looking at the stats between toyo and falken the actual diameter is slightly lower on the Toyos (36.5") vs. Falken (36.8") , im wondering if that 0.3" makes a difference for some? I have Toyo RT Trails and mine is dead on without having to change any of the axle settings at the 2770 circumference.

 

[Klutch]

Using 2770 my toyo's are dang close to gps speed. after relearn of pv, tcm and awd all dah lights go away but still has a p160 if you read the codes.

 

[ZooDad]

Using 2770 my toyo's are dang close to gps speed. after relearn of pv, tcm and awd all dah lights go away but still has a p160 if you read the codes.

Sounds like a “freeze frame” historical code

ZooDad

 

[Klutch]

Sounds like a “freeze frame” historical code

ZooDad

I don't understand what that means.

 

[blumhagen]

I don't understand what that means.

Probably that if you clear the code in forscan it will go away.

 

[ZooDad]

Freeze frame is a historical code not present at time of scan

 

[PaulCNY]

Bringing this thread back to life. So, I just installed 37x12.50x20 Baja Boss AT's on my '26. Right now I am between 2-3 mph off at highway speeds and obviously it gets lower as the speed reduces. Therefore, is the 2770 number still the preferred setting in forscan to readjust my speedometer? Then, I follow it up with the relearning of the other modules? Thanks for any advice you can give.

 

[Klutch]

Bringing this thread back to life. So, I just installed 37x12.50x20 Baja Boss AT's on my '26. Right now I am between 2-3 mph off at highway speeds and obviously it gets lower as the speed reduces. Therefore, is the 2770 number still the preferred setting in forscan to readjust my speedometer? Then, I follow it up with the relearning of the other modules? Thanks for any advice you can give.

Yeah I'm using it with my Toyo's and it's pretty much spot on. Anything larger than 2770 and i could not get the codes to go away.

 

[Painless]

I used 2799 and I am dead on all the way up to 80 mph. But mine is a 22.

 

[PaulCNY]

I used 2799 and I am dead on all the way up to 80 mph. But mine is a 22.

So, '23+ uses 2770, and pre '23 uses 2799?

 

[Painless]

So, '23+ uses 2770, and pre '23 uses 2799?

From my research 2799 should work on 22+, obviously I have not tried on anything other than a 22.

 

[NightForceFan]

So, '23+ uses 2770, and pre '23 uses 2799?

My 26 uses 2799 and works fine for my 37s. No codes.

 

[PaulCNY]

My 26 uses 2799 and works fine for my 37s. No codes.

Thanks for the heads up. Just curious, does anyone know what the difference is between 2799 and 2770 as far as accuracy?

 

[NightForceFan]

Thanks for the heads up. Just curious, does anyone know what the difference is between 2799 and 2770 as far as accuracy?

No clue, but 2799 is the largest number that works. For mine, it is dead on with my radar GPS.
37x12.50x18 Toyo RT

 

[PaulCNY]

No clue, but 2799 is the largest number that works. For mine, it is dead on with my radar GPS.
37x12.50x18 Toyo RT

I will try 2799 first this evening and see what happens. Fingers crossed. Thanks!

 

[PaulCNY]

FORScan updated with 2799 circumference entered. Went through initialization steps, cleared DTC’s, and now my Speedo is dead nuts accurate (I only went up to 70mph). No lights on dash and this method works perfectly! My Boss AT’s are a 36.7” so the 2799 was spot on. Maybe it’s in my mind, but it seemed the truck shifted a little better after the update?

 

[thetremorbuild]

Bookmarking this for when I go to 37s. I'm on 35x12.50R18 Falken AT4Ws now. I backed up my modules in FORScan before changing anything, and I'll do the same before touching the tire size setting.

 

[26PlatinumPLUSAG]

FORScan updated with 2799 circumference entered. Went through initialization steps, cleared DTC’s, and now my Speedo is dead nuts accurate (I only went up to 70mph). No lights on dash and this method works perfectly! My Boss AT’s are a 36.7” so the 2799 was spot on. Maybe it’s in my mind, but it seemed the truck shifted a little better after the update?

I am running 37"x 11.5 R20 Falken RT. I have been wanting to try this, but I've been scared. I did some other changes, no problem. Just scared to get some codes.

 

[MVI]

I am running 37"x 11.5 R20 Falken RT. I have been wanting to try this, but I've been scared. I did some other changes, no problem. Just scared to get some codes.

I'm not messing with it either for a 2 mph delta at 70 mph with 37's