Elvota

Was wondering if anyone knows what the ABS sensor on top of the rear diff picks up on? What does it use to track the speeds gears and such are moving? If one puts in aftermarket gears, does the sensor loose its ability to know what is going on back there?

I guess I am wondering whether there is something in the factory gear that the sensor reads.

Thanks

MTL_4runner

What vehicle is this regarding?

ABS sensors read a magnetic ring which can be located almost anywhere on the drivetrain (most often located at each wheel).

Can't say much more without knowing what vehicle.

Flamedx4

Seems to read the teeth on the ring gear. If you remove it and look inside, you see the teeth. Changing the number of teeth shouldn't matter, but some have reported a problem with it reading after a gear change. Tolerance might be the issue = distance from the ring gear. Normally they have to be very very close.

eric-the-red

2nd gens with rear anti-lock have 1 sensor on the rear diff. Looking at the manual it doesn't show anything on the differential. Looks like the sensor just determines if the ring gear is rotating or stopped.

snap-on

I thought the ring gears of ABS equiped trucks (of that age) had an ABS ring affixed next to the ring gear. looks like a saw blade with sq teeth. the sensor reads these sq teeth as opposed to the actuall teeth of the ring gear.

Flamedx4

With 4 wheel abs I would say that's probably always gonna be true. The controller needs to know if the fronts and rears are turning at different speeds (also needed for &*%$# traction control ) but for rear wheel abs turning/not turning is all it really needs to determine. I can tell you for certain that there was no tone ring inside my diff when I removed and regeared and reinstalled it.

Aha! In the FSM for rear wheel abs it says "inspect the ring gear (sensor rotor) for scratches, cracks, warping or missing teeth. If necessary, replace the ring gear." And shows the sensor at the teeth edges.
And in the function test for the sensor, all it's looking for is a signal. It's a signal/no signal function test. So it doesn't care what ring gear is in there, as long as the mag pickup can read off the serrations.

kurtdaniel

ive read that this ABS Speed Sensor system provides individual control of the front wheels, so they can both achieve maximum braking force.