can the speedometer be re-calibrated?

Paul M · Nov 22, 2012

Ditto...ours is dead on now at hwy speeds with the taller tires, but turning off the o/d really helps the ****** on faster dirt road drives as well as hilly pavement at our altitude.

tjkj2002 · Nov 22, 2012

Paul M said:
Ditto...ours is dead on now at hwy speeds with the taller tires, but turning off the o/d really helps the ****** on faster dirt road drives as well as hilly pavement at our altitude.

That's the thing is the PCM is programmed for the speedo being off with the stock tires.So by adding larger tires to get the speedo to read right it still is messing up the PCM and how the trans shifts.

Paul M · Nov 23, 2012

It's covert speed control...drivers assume manufacturers are honest. Who'd a thunk it?
You are right tho, need to get ours programmed for 30" diameter tires...regardless of exact speed or not, shift points feel "off".

tjkj2002 · Nov 23, 2012

Paul M said:
It's covert speed control...drivers assume manufacturers are honest. Who'd a thunk it?
You are right tho, need to get ours programmed for 30" diameter tires...regardless of exact speed or not, shift points feel "off".

OEM speedo's can be as much as 5mph from the factory,that is the acceptable limit.Only vehicles going for police use have calibrated speedo's,and must be kept calibrated every year.

Paul M · Nov 23, 2012

Exactly...but with today's tech you'd think speedo's would be more accurate +/- one or two mph under a stock setup.

J-Thompson · Nov 23, 2012

I have never recalibrated a damn thing on any of my rigs
the ones that were modified and the ones that were stock
Never had an issue with a single one
and there were several
Even on the 2 hot rods that had gears changed for better
"off the line" speed ,1 went from 3.07 to 4.10
Nothing
My TJ is going on 11 years old with 32-33" tall tires for the last
8 of those years and no recal of any type
and no issues
And don't give me the "it is older and different" crap
The JK guys are also not dealing with this feared speed o
being off crap they deal with it like I said

tjkj2002 · Nov 23, 2012

J-Thompson said:
I have never recalibrated a damn thing on any of my rigs
the ones that were modified and the ones that were stock
Never had an issue with a single one
and there were several
Even on the 2 hot rods that had gears changed for better
"off the line" speed ,1 went from 3.07 to 4.10
Nothing
My TJ is going on 11 years old with 32-33" tall tires for the last
8 of those years and no recal of any type
and no issues
And don't give me the "it is older and different" crap
The JK guys are also not dealing with this feared speed o
being off crap they deal with it like I said

The JK guy's are using the procal or superchips to fix the speedo in vast numbers and were hounding the afermarket hard for '11+ hacks.

And I will say "because they are older it's different" by the simple means that those trans are not full electronically shifted trans.Huge difference why the speedo does not even need to be close on a non-electroniclly shifted trans compared to a electronically shifted trans.A elelctroncially controlled trans relies on the speedo and compares it to other outputs from the engine for how it shifts.

IceColeNH · Nov 24, 2012

My speedo was dead on in the 03 Rene after installation of lift and 245 75 16. Of course at highway tire inflation levels. Only time shift points really were noticeably off was in the hills. Turning OD off was key.

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J-Thompson · Nov 24, 2012

tjkj2002 said:
The JK guy's are using the procal or superchips to fix the speedo in vast numbers and were hounding the afermarket hard for '11+ hacks.

Not the cheep a$$ guys I know
The only thing they do is recenter the wheel

Porkchop · Nov 24, 2012

What do you expect in Doucheville

J-Thompson · Nov 25, 2012

Porkchop said:
What do you expect in Doucheville

Not what I expect
It is how we roll
We don't worry about the small stuff
We know if we put taller tires on then we are going faster
then what the speed-o says if we don't regear
We also know if we regear then we are probably going slower
then what the speed-o says

Looks like we know how to use good ole common sense
How do you explain the rest?

Paul M · Nov 25, 2012

So it begs the question, Does it really make that much of a difference to go thru the trouble for slightly taller tires so shift points are more accurate? Maybe not.

When I put the new taller tires on someone on the forum had suggested a "fix" for recalibration...to disconnect the battery for fifteen minutes, hook it back up then go for a drive to allow the computer and sensors to relearn shift points. Seemed to improve when I did it but maybe that was my perception based on preferred outcome "that because it was suggested it would actually work." For now I'm just going to turn off the O/D.

tjkj2002 · Nov 26, 2012

Paul M said:
So it begs the question, Does it really make that much of a difference to go thru the trouble for slightly taller tires so shift points are more accurate? Maybe not.

When I put the new taller tires on someone on the forum had suggested a "fix" for recalibration...to disconnect the battery for fifteen minutes, hook it back up then go for a drive to allow the computer and sensors to relearn shift points. Seemed to improve when I did it but maybe that was my perception based on preferred outcome "that because it was suggested it would actually work." For now I'm just going to turn off the O/D.

Problem with that is it only works for a few drive cycles then the computers start to freak out when they see that the engine speed,trans input speed,and trans output speeds are wrong compared to what your ABS sensors are reading.Bad shifting,low mpg's,and exccesive heat build up in the trans results.

Paul M · Nov 26, 2012

Makes sense...next time I'm in town I'll pay the few bucks at the dealer to recalibrate the dang thing.

J-Thompson · Nov 26, 2012

tjkj2002 said:
Problem with that is it only works for a few drive cycles then the computers start to freak out when they see that the engine speed,trans input speed,and trans output speeds are wrong compared to what your ABS sensors are reading.Bad shifting,low mpg's,and exccesive heat build up in the trans results.

By this reasoning only ABS equipped KJ's would have problems
Because the ABS is the only link to wheel speed
But wait my '03 had the ABS option
So now explain why I had no shift issues and got 17-18 mpg
mixed driving with 245/75 MTR's?
Oh and the 2012 JK's have ABS
I want to say that an '04 LJ does as well
IIRC it was an option starting in '03 for the TJ and you don't
read about them need any "recalibrating"

tjkj2002 · Nov 26, 2012

J-Thompson said:
By this reasoning only ABS equipped KJ's would have problems
Because the ABS is the only link to wheel speed
But wait my '03 had the ABS option
So now explain why I had no shift issues and got 17-18 mpg
mixed driving with 245/75 MTR's?
Oh and the 2012 JK's have ABS
I want to say that an '04 LJ does as well
IIRC it was an option starting in '03 for the TJ and you don't
read about them need any "recalibrating"

Your also sitting pretty close to sea level and flat with no mountains to climb to get to work.Just picture I climb almost 1100' in altitude in 7 miles going to work each day.

bring it up here and you'll see why having the speedo corrected is needed.That 17-18mpg's would be 10-11mpg's in a heart beat with a un-adjusted speedo.

Ry' N Jen · Nov 27, 2012

Interesting this "can the speedometer be re-calibrated?" thread.
With the speedo/****** shift points reprogrammed {Pinion Reset}
and a good quality code reader/on board computer with speedometer
readout, and a new six inch screen GPS. Our KJ Speedo is F:favorites68:ed!

At certain speeds it 100% accurate. At other speeds the Jeeps speedo is off
by up to 15%.
The code reader is off by up to 10%

GPS?

I don't know, I got it less than 18 hours ago and am still learning how to use it.
It's brank spanin' new.
I know the speed reading on a GPS unit is extremely accurate so it's just different seeing it for the first few times.

Damn thing even tells ya when you are speeding!

Ya, pretty cool.

Paul M · Nov 27, 2012

GPS is accurate, but so are mile-markers along highways...I just go five miles to average out any minor discrepancies. The only time I notice weird shift points is in the hills (plus the altitude has a big affect.)

tjkj2002 · Nov 27, 2012

Ry' N Jen said:
Interesting this "can the speedometer be re-calibrated?" thread.
With the speedo/****** shift points reprogrammed {Pinion Reset}
and a good quality code reader/on board computer with speedometer
readout, and a new six inch screen GPS. Our KJ Speedo is F:favorites68:ed!

At certain speeds it 100% accurate. At other speeds the Jeeps speedo is off
by up to 15%.
The code reader is off by up to 10%

GPS?

I don't know, I got it less than 18 hours ago and am still learning how to use it.
It's brank spanin' new.
I know the speed reading on a GPS unit is extremely accurate so it's just different seeing it for the first few times.

Damn thing even tells ya when you are speeding!

Ya, pretty cool.

Paul M said:
GPS is accurate, but so are mile-markers along highways...I just go five miles to average out any minor discrepancies. The only time I notice weird shift points is in the hills (plus the altitude has a big affect.)

Explain this................

You must be registered for see images attach

Look at max speed,and yes it's in miles per hour.

Paul M · Nov 27, 2012

Sun spots...

Of course, maybe you accidentally hit the Warp Drive button...word has it that was a factory option on the Liberty MIB Interceptor model...maybe you got one of those by accident.

can the speedometer be re-calibrated?

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