2014 8-Speed after bigger tires.. vss reprogram?

localdanishdood · Jan 24, 2017

I am leveling my truck with bils this week and putting 35's on. I called my trusted mechanic to set up a mount/balance & alignment and he gave me the whole run down of why not to lift bushings, a-arms, stress, etc. The known possible faults, but bils set at 2.1 seem to be pretty safe.

One thing he did mention was the transmission that I over looked. After bigger tires the speedo will read differently throwing the 8 speed off as it electronically reads your speed to shift appropriately. Is this something I should/can bring to be re-programmed?

Are their any other things I should be doing after level/bigger tires?

H3MI UP · Jan 24, 2017

Yes you will need to re program for the bigger tires. You will also have added stress on components but it's just the price you pay. Things will wear out faster than if it was left stock. A lot of us know this going in and just deal with it when things wear out

DannyMK2 · Jan 24, 2017

your speedo will be off 3-4 mph. the transmission should shift fine. if you have the means if correcting the speedo, i would do it. otherwise i wouldnt worry about it personally.

blackbeautyhemi · Jan 24, 2017

Find out the revolutions per mile for your tire and the dealership can reprogram it.

localdanishdood · Jan 24, 2017

blackbeautyhemi said:
Find out the revolutions per mile for your tire and the dealership can reprogram it.

I'm actually running the same as you, 35" Trail Grapplers.. Do you know the revolutions per mile?

Tach_tech · Jan 24, 2017

blackbeautyhemi said:
Find out the revolutions per mile for your tire and the dealership can reprogram it.

No we can't. Long time ago we used to be able to program tire sizes based on revs per mile. That changed in the mid 2000s. Now we can only program tire sizes based on what's available from the factory. Usually we can get it close but not exact. You'll need an aftermarket programmer to get it 100%.

Pmexpert · Jan 24, 2017

I reprogrammed mine with diablosport. the only use of this gamepad)))
just chosen the right tire size there and that's it. But you can go to a local dealer, that can adjust gears and tire size as well. it will def be cheaper than buyin a tuner

H3MI UP · Jan 24, 2017

Tach_tech said:
No we can't. Long time ago we used to be able to program tire sizes based on revs per mile. That changed in the mid 2000s. Now we can only program tire sizes based on what's available from the factory. Usually we can get it close but not exact. You'll need an aftermarket programmer to get it 100%.

The dealership was able to do mine. They did the lift and installed the tires and rims. I checked to make sure the mph was on by another gps and it was

blackbeautyhemi · Jan 24, 2017

Tach_tech said:
No we can't. Long time ago we used to be able to program tire sizes based on revs per mile. That changed in the mid 2000s. Now we can only program tire sizes based on what's available from the factory. Usually we can get it close but not exact. You'll need an aftermarket programmer to get it 100%.

Yea that's wrong cause mine was done a couple years ago and was also done on a previous truck and several of my friends trucks. My dads a manager at our local dealership so I have good access to all that stuff. It's more accurate doing it that way than putting in the "size" on a programmer, with putting it in on my diablosport my speedometer would right on at 40 mph and off 4 mph at 70.

blackbeautyhemi · Jan 24, 2017

localdanishdood said:
I'm actually running the same as you, 35" Trail Grapplers.. Do you know the revolutions per mile?

On 18" wheels? For 35x12.5x18 it's 592 revolutions per mile.

Tach_tech · Jan 24, 2017

blackbeautyhemi said:
Yea that's wrong cause mine was done a couple years ago and was also done on a previous truck and several of my friends trucks. My dads a manager at our local dealership so I have good access to all that stuff. It's more accurate doing it that way than putting in the "size" on a programmer, with putting it in on my diablosport my speedometer would right on at 40 mph and off 4 mph at 70.

No no, it's right. I'm a tech for Chrysler and have been for going on 10 years. I have first hand access to wi tech as well as years of experience and being a certified "doctor in the house" meaning I've reached the highest training level possible from Chrysler. Not saying I know everything and always have more to learn. That being said, it's not possible to program tire size based on revs per mile anymore with the new trucks. If you have say a 2004 truck then yes, we can use revs per mile since that's done with the old DRB scan tool.If it's a newer truck, we program based on factory tire sizes available on any Ram truck wether it's a 1500 or 5500. So by using that and playing around with gear ratio programming, we get it pretty close.

Tach_tech · Jan 24, 2017

Hpstang said:
The dealership was able to do mine. They did the lift and installed the tires and rims. I checked to make sure the mph was on by another gps and it was

I never said we can't do it, we can. Just not by programming revs per mile on the newer trucks. Usually what we do is mess with available tire sizes as well as gear ratios. Usually it's pretty close, but it's difficult to get close if you're running much bigger than 35s.

A lot of dealers also purchased aftermarket programmers just to program tire sizes.

blackbeautyhemi · Jan 24, 2017

My buddies 2012 ram was done by that way because he emailed firestone for the revs per mile for that tire...

Tach_tech · Jan 25, 2017

blackbeautyhemi said:
My buddies 2012 ram was done by that way because he emailed firestone for the revs per mile for that tire...

Not with the wi tech factory scan tool. The factory scan tools haven't used revs per mile since the DRB and early Star Scan era.

Lots of dealers purchased aftermarket programmers specifically for adjusting tire sizes since Chrysler took that ability away and only gave factory sizes. Just recently they also took away the ability to set the tire pressure thresholds beyond factory settings.

2014 8-Speed after bigger tires.. vss reprogram?

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