VSS woes

[prayforsurf0]

My speedometer stopped working and I started having some weird transmission bumping. Got P0500 code (VSS). After buying the wrong VSS (transfer case mounted VSS) I went back and got the correct one that is mounted on the rear differential. I replaced the old sensor with the new and it still doesn't work.
I did notice that the new VSS sensor looks a little different than the old one. The old one has a smooth round cylinder that goes into the differential, the new one does not have a smooth cylinder, rather its more hexagonal shaped with concave sides. I did a search for the same part online and from the pictures it looks like all the replacement parts have those concave sides on the cylinder that goes into the differential.

I also noticed the new cylinder does not spin by hand, the old one does. Shouldnt I be able to spin the sensor by hand ?

Is it possible pieces of the old sensor broke off into the differential ?

 

[prayforsurf0]

Anyone ? I'm stumped. I'm getting 1 V at the plug when the key is on, engine off. The new sensor is in and the plug is clean and seated nicely. Only thing that is bugging me is that the new sensor doesn't spin (the part that goes into the differential). Is it supposed to spin, or does it read the axle speed magnetically ? No idea why this isn't fixed. The speedometer is reading intermittently.

 

[SoHK_alumni]

I could have swore that on your '98, the VSS is gear driven by the output shaft going to the drive shaft and the rear axle sensor is simply part of the ABS system.

On the '99 and newer ones, the ABS system uses the rear axle sensor as its input data and provides the same basic output signal as the VSS does for the rest of the vehicle.

The sensor in the axle picks up on the notches in a ring mounted to the differential, does not have any moving parts.

I would revisit the back of your transfer case, there should be a gear driven VSS there.

 

[jester1023]

Yep, the rear is for ABS. The actual VSS is mounted in the tail of the T-case on the driver side, angling down. It uses the same type of gear to drive it as does a regular speedometer cable. If the gear looks worn in the middle of the teeth, you may have a matching worn drive gear on the tail shaft...which warrants replacement of both gears. This is normally accompanied by a speedometer needle that bounces. If you just have a dead needle, it's probably the VSS or the gauge itself.

 

[SWIGIN]

I don't think so guys.

I just pulled my 98 T case and it had no wires or plugs on it.

Here it is next to a 4406 that does have a VSS in the tail but I don't need it for my speedo to work.