Wheel Speed Sensor

Wheel Speed Sensor

Postby Axmechanical [OP] » April 18th 2020, 8:05pm

If you are having wheel speed sensor faults thrown which in my 99 Safari resulted in the AWD light coming you may be looking for what the story is with changing a wheel speed sensor in the front wheel of an AWD safari. Wanted to share a few tidbits to help avoid some my lessons learned:
The "allen head" bolt that holds the sensor to the hub is in fact a mysterious 5 sided penta fastener head. No you are not seeing things, I was able to extract it by jamming a 3/16 hex into it and using a impact, apparently they sell bits for these things on amazon, regardless when you get it out the threads are M6x1, replace it with a regular metric allenhead fastener from store. The great thing about this repair is the sensors are available and reasonable from Rock A. The sensor I purchased however was different from the existing one I removed. This is where the tricky part starts. The sensor must be very close but not touching the notched wheel (reluctor) in the hub. From what I could discover the correct air gap is .02-.06. There is a lot of general discussion on the existing shim under the sensor. This shim may be fine if your new sensor is the same length as the one you remove. However the one I revived from Rock even though it was a GM part was way longer than the sensor I took out which I didn't discover until I had sheared the head off it. The existing sensor was .68 long. The new sensor is/was .703 long. Not good. This is what I did: Take electronic caliper and using the part that slides out the bottom measure the distance from the surface of the hub to the reluctor wheel tooth, try and get it at the tdc i/e closest to the hole. Mine is .6835. The air gap I chose is .04 so total distance from the edge of the hole to the top of the air gap is .643 The new delphi sensor is .703 so I needed .703-.643= .06 shim to keep the sensor .04 air gapped to the wheel. If you want to save yourself a try and discover put a couple pieces of tape on the top of the sensor and see if your wheel turns, do this with extreme gentleness to save your sensor, my masking tape is .003 a couple/three :screaming: layers will give you enough to validate your not touching. A couple of these items may be helpful if you are attempting this.
Original Poster [OP]
Fueling (1/8 tank)
Fueling (1/8 tank)
Years of Membership: Axmechanical has been a member for 5 full yearsAxmechanical has been a member for 5 full yearsAxmechanical has been a member for 5 full yearsAxmechanical has been a member for 5 full yearsAxmechanical has been a member for 5 full years
Posts: 16
Topics: 4
Joined: September 2015
Gender: Male
Alias (AKA): Control Guy
Van Model Year: 1999
Van Make/Model: GMC Safari
Extra Info: 4.3L AWD

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