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Reprogramming For Tire Size and Gear Ratios

ExplorerDMB

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Well, I finally figured out how to reprogram (for the speedo to read correctly and so on) for tire size and gear ratio changes in the 98-01 Explorers/Rangers/Mountys. I used a NGS (Factory Ford scan/program tool - no longer in use anymore) with all of its recent updates (up until last year I believe), and was able to go into the ABS system and change the settings manually. Now, as probably many of you know, I tried to go through the GEM Module to reprogram, but it would never take any of my programs/settings (http://www.explorerforum.com/forums/showthread.php?t=134477. Well, I basically back doored it going through the ABS module which is what the GEM module acually uses for the speedo. So with change the settings in the ABS module, it changes the GEM Module. Here is a helpful list:

98-01 -- Reprogramable through the GEM or ABS Module
91-97 -- Gear Change (for the transmission)

Now, Ford charges .7 hrs for a reprogram as described in the above links and in the post. It took possibly 3 minutes to change everything. Granted, I knew the Revolutions Per Mile ahead of time, but that would of taken just as long. Here is how you figure out your REVS/Mile:

Chalk Test:

Mark your tire at the bottom with a chalk pencil or something visible (also mark on the pavement) and then roll forward until it has made a full revolution and mark another mark on the pavement. Then measure between the two marks and that is 1 revolution. In my case mine came out to be 8' and 5"s which in turn changes to 101"! So now what? Here is something helpful:

1 mile = 5280 ft x 12" = 63,361 inches

Now, devide 63,361 inches by 101 inches (your one revolution) and you will end up with 627.33 Revs/Mile. Obviously each vehicle will be different (i.e. tire size), but my set up was 33" tall tires with 4.56:1 Gear Ratios.

Well, now that you have all these numbers what do you do? Well, do the following (in the NGS):

1. SELECT: SERVICE BAY FUNCTIONS
2. SELECT: ABS
3. SELECT: TIRE SIZE/AXLE RATIO CONFIGURE
a. The NGS Tester will display "DETERMINING MODULE PROTOCOL, PLEASE WAIT"
b. When NGS Tester is ready, press {TRIGGER} to continue.
4. ENTER TIRE SIZE/REVOLUTIONS PER MILE (REV/MILE)
5. SELECT: DONE


I know that not many of you have a NGS, but this is just so you know what happens when whoever does the reprogramming is doing and you can stay up to date. My speedo is in within 1-2mph! Use to be 5mph+ at 0-45mph and 10mph+ 55mph+! It's a wonderful thing now.

-Drew
 


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ExplorerDMB

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Just a small update: obviously with the speedometer reading wrong, the transmission didn't shift exactly where I needed it to shift - but now since it's fixed, it has cleaned up a bit and acts better and puts me at ease. I believe Jefe also expierenced this when he lifted his Explorer. Also, here's a picture of the Ford NGS:

fordngs.gif


-Drew
 




boominXplorer

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dude I love you. I just did this to my truck. You feel like your moving slow afterwards
 




ExplorerDMB

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boominXplorer said:
dude I love you. I just did this to my truck. You feel like your moving slow afterwards

HAHAH yup! That's hilarous cause I was driving after I did it and was like "holy shit...I must of been cruising like ass" (when I wasn't recalibrated). When did you do it to your Mounty? Did you use the NGS at ATI? U may be able to do it with the WDS, but I am not sure.

-Drew
 




ExplorerDMB

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For those of you who are looking into buying like the Superlift tru-Speed and other little items that cost over $100+, you should look into this before that, most of those just interrupt the signal from the VSS.

-Drew
 




Xzibit A

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yes you can do it with WDS, its probibly eaisier too but i dont have acceess to a WDS anymore ill just have to use the trusty ngs XL, BTW did you use the green card or red
 








Xzibit A

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what i dont get is how the computer sees the 4.56 gears you have, also instead of doing the chalk thing you could just measure the circumference or your tire( 33 x 3.14= 103.62)
 




Jbrobeck

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Xzibit A said:
what i dont get is how the computer sees the 4.56 gears you have, also instead of doing the chalk thing you could just measure the circumference or your tire( 33 x 3.14= 103.62)


The computer doesn't care what gear ratio you have when it comes to your speedometer, by reprogramming, it knows that one revolution of the axle (read by abs toner ring) = (x) inches and it calculates speed from there. It can then use that information to calculate shift points.

Problem with the measuring of the circumfrance of the tire is that with road deflection of the tire, the measurement can be incorrect, if you mark and roll the wheel under the load of the truck you get a more accurate reading. I am sure it would get you very close however.

Josh
 




ExplorerDMB

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Thank you Jbrobeck for clearing that up. Hope that anwered your questions Xzibit A!

-Drew
 




Xzibit A

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AH, i was thinking something along those lines but could quite get it, what about tread depth and air pressre, both of those will affect the roll lenght. that was the reason for me asking, point being on my truck one of the rear tires has like 1/8 inch more tread than the others should i measure the work tires, the newer tire or a brand new tire, know what i mean?
 




ExplorerDMB

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I understand. To be honest, it won't make that much of a change. I mean your numbers may be off by 3-5 counts, but shouldn't make your speedo so inaccurate. I would say even if it isn't exactly right, it should still be within 1-2 mph.

-Drew
 




Xzibit A

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thats what i was figureing so useing the circumference would be fine , so we can then make a big simple equation for the rpm.

63361/(tire height x 3.14)= rpm
 




Doug904

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I use the website...www.1010tires.com for the tire size calculator there as it has sizes in inches as well as metric ratings.

Also, one small thing to add on the tire and gear ratio adjustments. After 99' this could be done on the SOHC Explorer's in the PCM but it couldn't ever be done with a tuner on a 5.0 Explorer as they never put it in the PCM but rather in the GEM module.

Thanks, Doug.
 




CougarX

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Instead of going through all this tire chalking and calculating why don't you just go to your tire manufacturer's website and look up the revolutions per mile for your style and size of tire? I'm pretty sure all the tires sites I have ever looked at have this information.
 




ExplorerDMB

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CougarX said:
Instead of going through all this tire chalking and calculating why don't you just go to your tire manufacturer's website and look up the revolutions per mile for your style and size of tire? I'm pretty sure all the tires sites I have ever looked at have this information.

I don't see it for my tires - Atleast not on the Interco site.

http://www.intercotire.com/site34.php

-Drew
 




CougarX

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Alright, guess I havn't been to all the tire sites. I know BFG, Bridgestone, Firestone, and several others I've seen have it listed with all the tires specs.

In that case, let me reiterate.

Check your tire manufacturer's web site, and you may find the information you are looking for. Otherwise, check out BFGs site or find a site that does list revs/mile for their tires and you can match up your size to a tire that that company makes. It'll be as close to what you get with a chalk line.
 




ExplorerDMB

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True but the chalk test is a little more accurate, because of air pressure, rim width, thread wear, etc.

-Drew
 




Xzibit A

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yeah hes right i tried to halfass it and my speedo is off the other way now not bad but like 4-5 mph. for the best results do the chalk measure
 


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ExplorerDMB

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So who has reprogramed their vehicle for their tire size?

-Drew
 




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