I have a question for those in the know, I need to know what exactly the tone ring in the rear axle controls on a 99 4x4 Auto w/4wheel ABS.

I know it controls the ABS, but I'm not sure if it controls anything else like shift points and what not as it does on other trucks.

Thanks!

 

It varies from year to year IIRC, but I dont remember what years have which.

 

Yup, that I know. That is why I am hoping someone here will have access to the manuals and know specifically what 99 does.

 

Rerard From ORR covered this and now I cant find or remember what he ended up figuring out. One way to find out is unplug the sensor and drive the truck....

 

As far as shift points are concerned I was told by Fredness that the tone ring does not affect them. When ordering my bama xcal2 Fred informed me that he would not be able to correct my speedo because I have a 98. Having an automatic I was concerned if this would affect my shift points, however, he informed me that the shift points are determined by engine speed and not vehicle speed.

 

For 98~2000 only, the ABS sensor does double duty as the Vehicle Speed Sensor. So, it provides the raw signal that drives the corrected speed signal to the PCM, speedometer, speed control, etc.

The two primary inputs to the shift point calculation are throttle position and corrected vehicle speed. So, in that sense, the ABS sensor is directly related to the shift schedule.

 

Great. Figures I get the year that is going to cause me grief replacing the rear axle.

So what did they do on 98-00's that didn't have ABS?

 

All 98~2000s have ABS (RABS or 4WABS), so they all have that sensor.

 

Son of a... ok.

Thanks Bob!

 

you could swap your tcase out for a manual 1354 from an explorer, they had a speed sensor built into the case. I just got one and thats what im going to try and do. (at least I think its a speed sensor....)

 

That is a good point there about the transfercase...

I was always under the impression that the 98-00's took the speed from the transfercase already, and that was the reason why you couldn't reprogram the speedo on them with a programmer like you can newer trucks.... hmmm...

 

The reason that you can't reprogram the PCM to correct for speedometer errors is because the PCM is not involved in the speed calculation before 2001. For 2000-back, the PCM is an "end user" just like the speedometer or cruise control and the correction is done mechanically or in a different module depending on the year.

95~97 use a gear driven signal generator on the trans or transfer case, so the speedometer correction is done by interchanging the drive and driven gears, similar to a cable-driven speedometer correction.

98~2000 do the correction in one of two modules. RABS trucks do it in the GEM; 4WABS trucks do it in the 4WABS Module. A savvy dealer service department should be able to access those modules to do the correction but an aftermarket flash tuner (such as the SCT) cannot because it only changes the PCM program.

 

Interesting....

 

What do you think the guy who worked for Ford or whoever that designed that damned sensor would think were he reading this thread...

WOW, ya'll are some crazy-a$$, Ford Ranger loving son of a guns!!!