Weird speedometer issue

[justinlogue5_0]

All of a sudden while driving down the interstate at 75 mph with the cruise on I started noticing a surge (a quick power up and and then coast back down and repeat constantly). All the gauges were normal and I tapped the brake to turn off cruise and it went back to normal. Turn the cruise back on and it started surging again. I happened to glance over and noticed the digital speedometer reading on my Edge was bouncing up and down a couple miles at a time (up or down about 3 to 5 mph at a time). That explains why the cruise was acting up, the computer was trying to maintain a speed but the speed is jumping around. My actual speedometer gauge in the dash wasn't bouncing around? Did a quick google search and everyone said a bad VSS in the rear differential. Ok cool, quick easy fix......nope. New sensor and same thing. Now it is causing my anti-lock brakes to act funny. Hit the brakes and one minute the peddle is hard and next soft. There is no check engine or ABS light on. This happen to any one else? Where do I look? Supposed to head to the mountains pulling a camper in two weeks (of coarse) would really love to have this figured out/fixed before then. Thanks!

 

[Tiha]

What year are we working on?

Seems like there have been a lot of broken wire issues with VSS lately. Rubbed through along the frame rail, that type of thing.

Worst case your ring hear is missing some teeth on the reluctor wheel. Which would mean bigger problems. May not hurt to pull the rear diff cover and take a look if you can't find a bad wire.

I suppose the PSOM could also do it, but I think reading it on your edge means the PCM is seeing the same thing as the PSOM so most likely a sensor/wire issue.

 

[justinlogue5_0]

Sorry I forgot to mention it but I have a 2002 (5/02). I hooked up my auto enginuity and went down the road and there is def a skip in the signal. Checked all the wiring and couldn't find anything. So I pulled the sensor out, jacked up the rear end and with my finger in the hole slowly spun the rear end with my finger feeling the teeth and bad news. I am missing a tooth on the little speed ring. So I have two weeks basically to get this pulled apart ad rebuilt. These are 10.5 rear ends right?

 

[Tiha]

These are 10.5 rear ends right?

Correct. You have lots of options, they are plentiful in the used market.

Otherwise they are still popular enough that getting parts should not be difficult. Hopefully you caught it soon enough you can get by with just bearings.

 

[justinlogue5_0]

Thank you! Side note, Isn't the PSOM only on 97/98 models and down? Then it switches over to the newer sensors etc...?

 

[justinlogue5_0]

Well 200 miles in and so far so good. My rear end housing was ruined by a spun bearing/race. Best we can tell the previous owner destroyed the rear end which dented the speed-o gear which was ok until the bearing started going out and was letting the rear end "move" around causing the dented gear to move away from the sensor just enough it was loosing signal. Found a donor housing out of a 2006. That caused a whole bunch of issues but long story short, the whole rear end is now refurbished with new bearings and seals. All the back lash's etc... has been set correctly and even though I am paranoid of every sound or bump I feel it so far seems to be good as new again.

 

[Tiha]

Awesome. Glad you got it. Sorry I missed the PSOM post. I honestly don't know. I have a 95. So that is in the back of my mind.

I think we all do the same thing. Have a guy that works for me, a life long mechanic. Transmission went out of his pickup. He rebuilt it, didn't use cheap parts. It works great, but he refuses to drive it for fear it will burn up again.
So now he sold it.

He does that with everything. Just be happy we don't live with that much fear.