pinion reset

[gtommec]

okay so I need to get my speedometer calibrated for the 245/75/16s but I am having an issue getting it done. Most of the dealerships that I have asked just straight up said no it can't be done. Now here is my current situation, My best friend teaches auto mechanics at one of the local community colleges here and one of his best students works at a local Jeep dealer, we asked him about it and he said he would ask his team leader about it. Now they said that they would reset my pinion for free 'in the interest of education' but both he and his team leader could not figure out how to do it. Does anyone have experience actually doing this themselves (read: at dealer) or can anyone give me like step by step directions as to where to find the pinion reset in the tool?

 

[Porkchop]

You need the revs reprogramed.

 

[LibertyTC]

Reprogramming done on one of those fancy $tar -scan tools.
Ryan had his completed at a Dealer, he was their first customer to do this.
Tire size (elaborate calculation required) of what is needed for 75's_____?
They figured it out. That is all I know, it may be in FSM anyone?

 

[Minimike]

I used to do on all sorts of vehicles. Was even able to do it to my old 97 Dodge Stratus. Most PCM's have a section that you can either change the pinion ratio (software, which you usually need a chart for) or enter in a tire size and the PCM will do the rest. On all the new ford all we had to do was enter in the tire size. I will ask my local dealership what can be done. They are very good at what they do there and they work on a lot of modified vehicles.

Whats is with

You need the revs reprogramed.

.....

That makes no sense what so ever...... You cannot program a rev... and if you are referring to RPM (revolutions per minute) there is NO WAY to program it. It simply shows engine speed.

Please do not post if you do not know what you are talking. No advice is better then bad advice.

 

[Neal]

The term RPM relative to tires, means revolutions per mile. Which is a valid statement.

 

[Minimike]

Yeah except he didn't say RPM... Also been in the industry a long time, never heard RPM used for revolutions per miles, seems silly. Vehicle speed measurements are taken from the transmission output shaft SS. Anywho before an argument breaks out lets not highjack this thread.

 

[Porkchop]

I used to do on all sorts of vehicles. Was even able to do it to my old 97 Dodge Stratus. Most PCM's have a section that you can either change the pinion ratio (software, which you usually need a chart for) or enter in a tire size and the PCM will do the rest. On all the new ford all we had to do was enter in the tire size. I will ask my local dealership what can be done. They are very good at what they do there and they work on a lot of modified vehicles.

Whats is with .....

That makes no sense what so ever...... You cannot program a rev... and if you are referring to RPM (revolutions per minute) there is NO WAY to program it. It simply shows engine speed.

Please do not post if you do not know what you are talking. No advice is better then bad advice.

Why do you say stupid shit like this (you dont know me) revs is short fot ravalations as I was on my droid phone and was just making it short
And if you brought it in to me and said I need the revs reprogramed for the tire size
I would say ok as any good tech would do and not be a snob abought it.

 

[yellocoyote]

(popcorn)

 

[LibertyFever]

I had my dealership configure my 04 Liberty's PCM for my LT245/75R16 AT's. I believe the 02's to the 07's you configure the tire size and that the 07's and above you have to configure revs. Am I right or full of sh*t?

 

[KJJosh]

Dealership had to configure my 07 to use revs

 

[Minimike]

@ jeh200284 How much did you find it changed the speed? I'm getting some new tires that are very close to your Duratrac's.

 

[LibertyFever]

@ jeh200284 How much did you find it changed the speed? I'm getting some new tires that are very close to your Duratrac's.

You want to hear something odd? Even though I've had my PCM modified for bigger tires the speedometer is still off (reads low) but my MaxiiTrip reads the correct speed. Both get the same data from the PCM.

 

[Minimike]

Weird... I have a GPS which tells me that my actual speed is about 8km/h slower then what my speedometer reads. Currently my tires are the stock 17" from Jeep. So when my speedometer reads 80km/h I'm actually doing about 72km/h. No wonder I keep getting passed

 

[KJJosh]

You want to hear something odd? Even though I've had my PCM modified for bigger tires the speedometer is still off (reads low) but my MaxiiTrip reads the correct speed. Both get the same data from the PCM.

I'm not the only one!!!!!!!!!! When the speedo is showing 65 I'm doing 70-72

Dealer has no clue

 

[KJJosh]

Weird... I have a GPS which tells me that my actual speed is about 8km/h slower then what my speedometer reads. Currently my tires are the stock 17" from Jeep. So when my speedometer reads 80km/h I'm actually doing about 72km/h. No wonder I keep getting passed

Leave it ALONE!!! I had 17 inch rims and when I went to the 245's the speedo was correct. The only reason I had the speedo work done was the ****** was shifting weird.

 

[Minimike]

Thanks for the heads up jeh200284 It's nice to have the GPS for comparison reasons.

 

[LibertyFever]

Weird... I have a GPS which tells me that my actual speed is about 8km/h slower then what my speedometer reads. Currently my tires are the stock 17" from Jeep. So when my speedometer reads 80km/h I'm actually doing about 72km/h. No wonder I keep getting passed

And more importantly you'll never get a speeding ticket :icon_lol:

 

[Minimike]

And more importantly you'll never get a speeding ticket

Yeah that's a good thing. Been driving for 10 years and no violations! yay. I've been hit 5 times.... Every time I was hit my car was parked and I wasn't in it. Darn people! 2 of the 5 hits I couldn't drive away from.

 

[Bullett55]

okay so I need to get my speedometer calibrated for the 245/75/16s but I am having an issue getting it done. Most of the dealerships that I have asked just straight up said no it can't be done. .........

Same issue. '05 Rennie 4X4. Did OME lift & went to 245/75R16s from the OEM 235/70R16s. 235/70s run ~720 revs/mi. 245/75s run ~686 revs/mi. So Jeep now thinks it's going 5% slower than it actually is. Dealer attempted to change pinion ratio..., BUT they discovered, after numerous attempts, that the computer would not accept anything less than the 720 revs per mile. Whenever they tried to input revs per mi less than 720, the speedo would become inoperative. So speedo continues to read 5% slow (nbd). Dealer also discovered that '06 and up they just dial in the tire size and your supposedly(?) good to go, but '05 you input the revs per mile..., and the computer will not accept a number lower than 720 rev/mi. Makes no sense to me..., who puts smaller tires on a Jeep??

Can anyone confirm or deny this information is correct? Thx

 

[Ry' N Jen]

okay so I need to get my speedometer calibrated for the 245/75/16s but I am having an issue getting it done. Most of the dealerships that I have asked just straight up said no it can't be done. Now here is my current situation, My best friend teaches auto mechanics at one of the local community colleges here and one of his best students works at a local Jeep dealer, we asked him about it and he said he would ask his team leader about it. Now they said that they would reset my pinion for free 'in the interest of education' but both he and his team leader could not figure out how to do it. Does anyone have experience actually doing this themselves (read: at dealer) or can anyone give me like step by step directions as to where to find the pinion reset in the tool?

I went to the Dealership we always deal with and asked them if they could do it
and they said "They didn't know, but would ask!"
Once I spoke to the mechanic who was willing to try doing it with the "Snap On" computer all he wanted to know in addition to the tire size was the Revolutions
per mileKm for 245-75-16" tires.
Which is 661.93 Rev's per mile/ 411.06 Rev's per Km and he plugged them into the hand held computer and it was done!
No rocket science or Voodoo involved.
Free of charge.