Gear change

pdmustgt2 · Post by **pdmustgt2** » Thu May 24, 2007 12:31 am

My 99 ranger with 01 mountaineer 5.0 is still running good. I still got the 4.10 gear ratio going to put the mountaineer rear axle and and front axle in that are 3.73 ratio. Is there something I need to change in the GEM computer to make the speedo work right or will it see the change and read right?

AllanD · Post by **AllanD** » Thu Jun 07, 2007 6:14 am

On your truck the speedo is driven electronically from the signal
"borrowed" from the RABS sensor on the rear axle.

Since the speedo is in essence driven by axle carrier RPM
changing the gears has no effect whatsoever on speedometer accuracy.

If you change tire sizes however...

OR if you have a truck originally equipped with a 7.5" axle and you upgrade to an 8.8" then you have a need to reprogram the GEM module.

AD

broncobowsher · Post by **broncobowsher** » Thu Jun 07, 2007 8:02 pm

AllanD wrote:
OR if you have a truck originally equipped with a 7.5" axle and you upgrade to an 8.8" then you have a need to reprogram the GEM module.

AD

Are you sure about this? Every ford truck I have ever checked has 108 teeth on the carrier. The computer doesn't know ring size, only counts the teeth as they go by.

pdmustgt2 · Post by **pdmustgt2** » Fri Jun 08, 2007 11:32 pm

Yes I know the rear abs sensor is also used as a speed sensor. But the front sba sensors are used too. I had the rear abs sensor go out it still had speedo even after I unplugged it. I hope it doesn't mess up the speedo reading I can only think how much ford dealership will charge to change it. Or charge you say they can't change it

1999 ranger supercab 4x4 4.0 now 5.0 engine

pdmustgt2 · Post by **pdmustgt2** » Tue Jun 26, 2007 12:24 pm

I don't know what I was thinking the speed sensor see wheel speed not gear speed like off the back of the trans. So it doesn't matter what gear ratio that is in.

Slap me silly