Speedo recal

[MartyD]

I need to know how I need to go about recal'ing me speedo for larger tires. Before ya'll get started, I HAVE done multiple searches on this, and every answer seemed to be different. I have a '96 Sport 4x4. I went from 235/75/15's to 31x10.5x15's. I know I need to recal, my question is can I do it thru the computer or do I require a speedo gear change? I have seen some say it is electronic after 95, others say after 98. Can someone that KNOWS give me a definative answer? Thanks in advance.

 

[ExplorerDMB]

I am currently in the process of reprogramming my computer to accept the bigger tires and gear ratio change. Now, I'm pretty sure the 98+ (2nd gens) are all computer based speedos and not gear driven. So, I doubt you can reprogram your computer. I might even get my computer reprogrammed tomorrow (tuesday) but I have to see how my schedule works out.

Here is a link for you:

GEM Module Reprogramming

Talk with Doug of Bama Chips to see if theres anything else you can do. Good luck.

-Drew

 

[MartyD]

Ok, I know its been a while, but I've been thinking about this (not full time mind you...lol) and am still confused. I thought 2nd gen Xs were those built 95-2001. They all are the newer body style and use the OBDII system. So my question still stands. Can my '96 Sport speedo be recal'ed using the computer or do I need a new speedo drive gear? Also, I've read the descriptions of how to calculate which gear I would need, if indeed i need one, and there HAS to be an easier way to figure it out. Can anyone she some light on either of these questions?

 

[ExplorerDMB]

I gave you a reply -- and it still stands: NO you cannot reprogram your computer to recal. the speedo. OBDII is just the diagnostic program - has nothing really to do with the speedo. There is no "mandate" on making manufacturers use electronics over mechanical for their speedos.

-Drew

 

[Truck39Trash]

I have a'97 and am curious about this as well. Where would I go to find a gear to change the speedo when I change the tire from stock 235 to 31's? Is there anyone that can help or am I enraging people by playing a broken record? I aplogize if I am but internet searches and some phone calls have proved to be dead ends.

 

[Blee1099]

http://www.explorerforum.com/forums/showpost.php?p=89925&postcount=9

 

[Truck39Trash]

Thanks for that link I read that post before i posted the above but I have 235's I was planning on 31's so his gear choice may be different because he has 265's, so i might be switching to those if I can't find an accurate gear for the 31's even though i am aware the tires are very close in size. I work p/t at a chrysler dealer and my service manager was a ford tech at one time he confirmed for me that 1997 Xs used a cable and not the computer. He did state that with the bigger tires I would have a problem with the radius/radial? arm bushings going bad very quickly, did anyone have that problem?

 

[ExplorerDMB]

so I now know that I have to replace the speedo gear.

Wish mine was that easy.

 

[Truck39Trash]

Stupid question time. I think i have figured it out but I am asking because I want confirmation. Every time I drive by one of those radar speed signs that the cops post all over the beach I check to see if it matches my speedo in my car. Every time my speedo says i am going 2-3mph faster than the radar. I've wondered what causes that. The only thing I can think of is the factory tires were bigger than what my father reeplaced them with. Maybe the ex is calibrated for 245s not 235s. I am using multiple radars so I don't think they are off but maybe. Any thoughts?

 

[ExplorerDMB]

I don't like those radars - those are very cheesy and probably aren't reliable at all. i believe 235/75/15s (or same diameter) came on the explorer - no other sizes (besides different wheel sizes, but the same overall size).

-Drew

 

[CDW6212R]

To check for a mechanical speedo gear in trans, look at the left rear of the trans, for a speedo output drive. Before all electronic systems, F.ord used a mechanical gear, driving a electronic sensor. If through 97 the sensor is back there on the trans, then there will be a gear that can be changed.

BTW, 15" Explorer tires are 29" tall, and 16" Explorer tires are 30" tall. The 30" tires create a more accurate speedometer reading. The speedometer on 15" Explorers reads high. I changed my 1998 model from 15's(29") to 17's(29"), and now 18's(30.5"), and my speedometer is more accurate than ever before. I show 1-2mph under actual at highway speeds.

30" tire height is about what the factory speedometers are calibrated for. Good luck,