ABS Wheel Sensor Replacement 1996 Chevy 3/4 Ton 4X4

[j cAT]

Originally Posted by tinkering

I did the cranking AC voltage output test. The passenger side sensor put out 0.4 VAC while cranking the hub with a socket on a lug stud; as fast as I could. Guess what? The drivers side produced zero VAC! That is very encouraging to me.Now I have thicker suspicions that the wrong hub is on the drivers side. Both of the wheel sensors measured 1100 ohms so I was expecting to see some kind of out put there. I am going to order the correct hub and do a visual comparison; I will also check the ring gear for fouling, wear and/or breakage on the next above freezing day we get here.

good work you will be an expert with these type failures.

[rhandwor]

Originally Posted by tinkering

I did the cranking AC voltage output test. The passenger side sensor put out 0.4 VAC while cranking the hub with a socket on a lug stud; as fast as I could. Guess what? The drivers side produced zero VAC! That is very encouraging to me.Now I have thicker suspicions that the wrong hub is on the drivers side. Both of the wheel sensors measured 1100 ohms so I was expecting to see some kind of out put there. I am going to order the correct hub and do a visual comparison; I will also check the ring gear for fouling, wear and/or breakage on the next above freezing day we get here.

The temperatures I observed on the internet for your area you need a wood burner for your garage. The radiant heaters for small propane tanks will take out the chill in a garage.

[tinkering]

Originally Posted by rhandwor

The temperatures I observed on the internet for your area you need a wood burner for your garage. The radiant heaters for small propane tanks will take out the chill in a garage.

I've got a wood stove and a radiant heater for the bottle but my garage isn't built yet; sooon
The weather is going to be above zero for a couple of days; maybe I can get some things done.

[tinkering]

Originally Posted by j cAT

good work you will be an expert with these type failures.

Thanks, it feels more hopeful now. I'll let you know when I get the hub changed out. Maybe this thread will be of some use to someone else too.

[tinkering]

Originally Posted by tinkering

I did the cranking AC voltage output test. The passenger side sensor put out 0.4 VAC while cranking the hub with a socket on a lug stud; as fast as I could. Guess what? The drivers side produced zero VAC! That is very encouraging to me.Now I have thicker suspicions that the wrong hub is on the drivers side. Both of the wheel sensors measured 1100 ohms so I was expecting to see some kind of out put there. I am going to order the correct hub and do a visual comparison; I will also check the ring gear for fouling, wear and/or breakage on the next above freezing day we get here.

The parts guy says it's the same hub for both sides. That would explain why the driver's sensor would have to be mounted upside down compared to the passenger sensor. I took the driver's hub off. I could now see a second sensor mounting screw hole; there is one on either side of the sensor hole on the hub. The second hole was hiding under a bunch of crud. Now I am able to mount the sensor with the cable pointing inboard. That is good in itself but when I got the hub off and had a better look, I saw that the sensor was not in fact all the way flush with the hub. I was working by feel when the hub was still on; when I thought the screw felt tight, the sensor was actually bound in the hole; it was a good 1/16 inch shy of flush. I got it all cleaned up and properly installed. The prevailing trouble may have been the driver's sensor was not mounted flush which would mean an enormous air gap.

When I redid the driver's side cranking AC voltage output test I achieved 1.2 VAC. That is more than j cAT said to expect. j cAT is that OK? On the previous day I achieved only .4 VAC on the passenger side but that was with the brake caliper drag limiting top RPM. I have that caliper off now, so tomorrow I will redo the passenger side cranking AC voltage output test. I hope to achieve an output similar to the driver's side. How close does it have to be to satisfy computer parameters?

I also looked through the sensor hole to inspect the reluctor gear. There was a ton of blue grease in there. Using a screwdriver, I stuffed a rag down through the hole, to make contact with the reluctor teeth. I turned the hub around by hand, intending to swab out a bunch of that grease; I did that a few times. All of the grease appeared to be very clean (no grit grime or metallic filings). There is a bit of grease still between the teeth; I can't get it perfectly wiped without pulling the hub apart. I think it is good enough.

I will let you know my results tomorrow.

[j cAT]

Originally Posted by tinkering

The parts guy says it's the same hub for both sides. That would explain why the driver's sensor would have to be mounted upside down compared to the passenger sensor. I took the driver's hub off. I could now see a second sensor mounting screw hole; there is one on either side of the sensor hole on the hub. The second hole was hiding under a bunch of crud. Now I am able to mount the sensor with the cable pointing inboard. That is good in itself but when I got the hub off and had a better look, I saw that the sensor was not in fact all the way flush with the hub. I was working by feel when the hub was still on; when I thought the screw felt tight, the sensor was actually bound in the hole; it was a good 1/16 inch shy of flush. I got it all cleaned up and properly installed. The prevailing trouble may have been the driver's sensor was not mounted flush which would mean an enormous air gap.

When I redid the driver's side cranking AC voltage output test I achieved 1.2 VAC. That is more than j cAT said to expect. j cAT is that OK? On the previous day I achieved only .4 VAC on the passenger side but that was with the brake caliper drag limiting top RPM. I have that caliper off now, so tomorrow I will redo the passenger side cranking AC voltage output test. I hope to achieve an output similar to the driver's side. How close does it have to be to satisfy computer parameters?

I also looked through the sensor hole to inspect the reluctor gear. There was a ton of blue grease in there. Using a screwdriver, I stuffed a rag down through the hole, to make contact with the reluctor teeth. I turned the hub around by hand, intending to swab out a bunch of that grease; I did that a few times. All of the grease appeared to be very clean (no grit grime or metallic filings). There is a bit of grease still between the teeth; I can't get it perfectly wiped without pulling the hub apart. I think it is good enough.

I will let you know my results tomorrow.

do not worry about the grease if it is clean. it is OK to have grease on the sensor encoder wheel. on the volts ac being more than the .4 volts this can happen if the sensor is too close. the hub manufacturers add a small shim to correct for this. you want the voltage to be about the same , does not have to be exactly the same. 1.2 is a little high if you did crank at the same speed on each side.

[tinkering]

Originally Posted by j cAT

do not worry about the grease if it is clean. it is OK to have grease on the sensor encoder wheel. on the volts ac being more than the .4 volts this can happen if the sensor is too close. the hub manufacturers add a small shim to correct for this. you want the voltage to be about the same , does not have to be exactly the same. 1.2 is a little high if you did crank at the same speed on each side.

I cranked both sides as fast as I could (maybe 3 or 4 RPS. Is this too fast?). This AM, the passenger side now produces .6 VAC after taking the caliper (drag) off. That is still .6 VAC difference between the two sides.
Should I try to shim the 1.2 VAC side out a bit to lower the VAC, or take the hub off the .6 side and see if I can clean it up to get the voltage up closer to the 1.2 VAC side? I am going to take the .6 VAC hub off and clean up the sensor mounting surface to see if the I can get the VAC to go up.
If I go the shim route, where do you get shims? I didn't see any at the wreckers; I was watching for them. Can I make one out of shim stock, or a tin can or something; how thick should I go?

Here is another question idea? Would it work for me to file a wee bit off of the end of the sensor, to increase the air gap; maybe .010" - .020"? I have an old sensor I could experiment with, or better yet maybe I should just get busy and make a couple of shims?

[j cAT]

Originally Posted by tinkering

I cranked both sides as fast as I could (maybe 3 or 4 RPS. Is this too fast?). This AM, the passenger side now produces .6 VAC after taking the caliper (drag) off. That is still .6 VAC difference between the two sides.
Should I try to shim the 1.2 VAC side out a bit to lower the VAC, or take the hub off the .6 side and see if I can clean it up to get the voltage up closer to the 1.2 VAC side? I am going to take the .6 VAC hub off and clean up the sensor mounting surface to see if the I can get the VAC to go up.
If I go the shim route, where do you get shims? I didn't see any at the wreckers; I was watching for them. Can I make one out of shim stock, or a tin can or something; how thick should I go?

Here is another question idea? Would it work for me to file a wee bit off of the end of the sensor, to increase the air gap; maybe .010" - .020"? I have an old sensor I could experiment with, or better yet maybe I should just get busy and make a couple of shims?

starter shim kit has the various thickness you need. just stick an edge in under the sensor with it locked in place and see what you get . these are stamped or use you shim tool to determine what size shim needed.

[tinkering]

Originally Posted by tinkering

I cranked both sides as fast as I could (maybe 3 or 4 RPS. Is this too fast?). This AM, the passenger side now produces .6 VAC after taking the caliper (drag) off. That is still .6 VAC difference between the two sides.
Should I try to shim the 1.2 VAC side out a bit to lower the VAC, or take the hub off the .6 side and see if I can clean it up to get the voltage up closer to the 1.2 VAC side? I am going to take the .6 VAC hub off and clean up the sensor mounting surface to see if the I can get the VAC to go up...

OK, I elected to pull the sensor out of the passenger side hub (the one that was delivering .6 VAC) to see if I could get the output to increase by cleaning up rust and corrosion that might be present at the mounting surface; it paid off. Although the sensor coil WOULD NOT come out of the hole, despite all of my patient coaxing, the plastic coil sheath stayed in the hole (I managed to retrieve it using a hooked tool; keeping the hub inverted so nothing would fall inside). I elected to replace both sides with brand new sensor units (I do not want to have to take the thing apart again, so I sprung for the $125.00). I applied white lithium wheel bearing grease to the new sensors before installing them in the holes.

Someone described turning the hub at approximately 1 RPS for the 'AC voltage cranking output test'; so for this last test I used 1 RPS; both side's outputs were balanced at around 0.5 VAC. If I crank like a madman I am able to reach about 1.2 VAC. I think the 0.5 VAC at 1 RPS looks right to me.

I also elected at this time to change the routing of the sensor cables. The manufacturer ran it between the backing plate and the steering knuckle, where there is not enough room for the sensor coil to pass through; this made it necessary to remove the hub to change the sensor. I ran the cable along the inboard side of the steering knuckle, and then up to the 'cable guide bracket' fastened to one of the upper ball joint mounting bolts. I made sure I gave the cable the slack required when the wheel is turned to the limit. In my opinion, this is a nice improvement.

After all these ABS repairs and test results on the front wheels, I will be surprised if I have to move on to the ABS computer or the ABS valve body.
I should be finished the rest of the repairs on the truck tomorrow, so I will post the ABS road test results then

[tinkering]

That's it! The road test proved a success. The ABS trouble is gone, and a few improvements have been made too. I am happy too, that I don't have to go into the computer or the valve body.

Thank you j cAT and everybody for your fantastic help!!

[j cAT]

Originally Posted by tinkering

That's it! The road test proved a success. The ABS trouble is gone, and a few improvements have been made too. I am happy too, that I don't have to go into the computer or the valve body.

Thank you j cAT and everybody for your fantastic help!!

it did take some time but the cost was very much cheaper than a repair shop. I do not have the knowledge of your emergency brake cables. I did not have help on that issue you had.

with the info on your abs repair I believe that this will be working properly for a good amount of time. good luck..

[tinkering]

Originally Posted by j cAT

it did take some time but the cost was very much cheaper than a repair shop. I do not have the knowledge of your emergency brake cables. I did not have help on that issue you had.

with the info on your abs repair I believe that this will be working properly for a good amount of time. good luck..

Thanks a bunch again j cAT. It is such a joy not to see the ABS light. The repair shop bill for the ABS, and the other repairs I did would have flattened my wallet.

We did a bunch of pictures of the E brake issues. You might find it a bit interesting; I am going to post them and the results at http://www.automotiveforums.com/vbul...07491&posted=1
So far, I got the E Brake working but the pedal could be higher. That is all I am going to do to it for now; it is 30 below today.