steel powder in rear differential

[Greenie]

It's been a long time since I changed the oil in the rear end - maybe 50K miles. The truck has 265K miles, I've owned it since new. The speedometer jumps between 65-75, I pulled the sensor out and found it covered with steel filings. The oil level plug has a magnet too, it was full of filings. I pulled the rear cover off, all looks good, some steel powder in the cavities in the bottom of the casting. No noise, leaks, looseness, no problems whatsoever.
Questions...
Can steel filings in the oil and on the sensor make it read the speed incorrectly?
Is it normal to make so much filings in 50K miles?

 

[dsltech83]

Is this a limited slip axle? Could be filings from metal clutch plates. Also could be from the spider gears, have you taken them out of the differential case?

 

[sle2115]

I'm not familiar with the 93's, but my 87 has the rear axle sensor and the speedo cable in to the transfer case. The sensor in the rear end only senses for anti lock brakes, but that might have changed in later years.

 

[flareside_thun]

Yes, not only can crap stuck to the sensor cause a wrong speedometer reading but, it can also make an electronic automatic transmission shift differently (read: uncomfortably;funny)

 

[itsacrazyasian]

I'm not familiar with the 93's, but my 87 has the rear axle sensor and the speedo cable in to the transfer case. The sensor in the rear end only senses for anti lock brakes, but that might have changed in later years.

92+ use the rear sensor for speedo/abs and trans shifting if you have a E4OD. The speed sensor is cheap. I'd go ahead and replace it. Clean the diff sump out and refill with new fluid. If its tight and quiet.

 

[Greenie]

I did replace the sensor last fall with a napa part because the transmission was acting up (OD light flashing, hard shifts) and setting codes. The new sensor did stop the problem but at speeds above 60mph the speedometer needle would jump 10-15 miles per hour. Just recently it started making the OD light flash. I've always changed gear oil every couple of years and used the Ford friction modifier, but the limited slip hasn't worked well for years. The differential is quiet and has no other problem. What I'm hearing is I since I've changed the oil and cleaned the magnets I should run it, it's just normal wear.