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post #1 of (permalink) Old 01-28-2019, 05:10 PM Thread Starter
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ABS issues

Long story...

2003 F350 7.3 with 4 wheel ABS

About 3 years ago, I noticed a strange sound like a pump kicking on, and slight brake pedal feel when slowly stopping at a stop sign or light. It would occur at about 15 mph, and stop at about 7 mph. Sounded like the ABS pump activating.

No ABS light or codes at this time.

Based on some advice, I changed out the sensor in the rear end, but it did not stop the pump sound. A couple weeks later, the pump sound quit, and at the same time, the ABS light came on. Likely the ABS pump and or module went bad from activating every time I stopped.

About a week after that, the ring and pinion had a failure, and I had the rear end rebuilt...new ring and pinion.

ABS light still on, no pump sound.

A year later, a second ring and pinion failure, due to first shop using a short pinion, instead of a long pinion, resulting in the pinion nut and yoke coming off at 60 mph while towing the camper, and a destroyed ring and pinion....rebuilt, with a correct new ring and pinion.

ABS light still on, no pump sound.

Finally get tired of looking at the ABS light, try new sensor again, light still on, no pump sound. So I get it checked out at a decent local shop, they say, bad ABS module and or pump...great. Get one from salvage yard, get it put in, bled, codes cleared, and WALA...no ABS light. But now, the pump is back to doing what it did 3 years ago...kicking in at about 15 mph, and out at about 7 mph, NO ABS light or codes.

Throw in new sensor...no luck, pump still kicking in, no light

Run FORSCAN. LF and RF ABS sensors reading good and equal, rear ABS speed is equal to the fronts, but the signal on graph mode shows a bunch of downward spikes, like a loss of signal, and in gauge mode, the rear shows the needle dropping down and back up about every 5-15 seconds

NO ABS light, no codes, pump still kicking in when stopping.

Unplug rear sensor...No rear input signal seen by FORSCAN, and the ABS light comes on, BUT, the ABS pump stops kicking in. LF and RF read good.

Plug the sensor back in, ABS light goes out, pump starts kicking in at the same 15 mph-7 mph range.

I'm lost at this point

Could it be the tone ring? Maybe it was damaged when the ring and pinion started going bad during the first instance of damage.

Anyone have any thoughts on what to do next?
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