speed/abs sensor

GT347SC

GT347SC

Member
Ive read the old threads about the speed sensor on the rear end but didnt see anyone mention what mine is doing directly. My speedo is solid up to about 45 then starts to bounce between 45-60 and gets worse the faster you go. The part i havent seen addressed is that if i let off the gas the speedo will stop bouncing and stay steady until you start to accelerate again. I have replaced the sensor and it got better but i have not tried filling any off the sensor as i saw in other threads (its too HOT). I pulled the cover last week to inspect and the spider gears are in bad shape so im looking into replacing the tracloc this winter. The gears have howled for a while so i was going to replace them anyway.

Any other things i should look at? I just need it to last till it cools off because im not working on it in 109 degree heat.
 
Well from the sounds of it the carrier might have some movement. Did you check the carrier bearings when you had the rear open?
 
Before I fixed my sensor, mine did the same thing you described. It would be steady as long as the speed dropped, then would bounce under acceleration. Replace the sensor and tightened the air gap and all was good.
 
Bearings were tight. No slack there. I kind of suspected the gap to be the problem. I still have oe sensor so ill mic the depth of it and compare to the new one tonight (when the temp drops to 95)
 
The sensor & its depth are probably fine. The bouncing needle is probably a result of the worn spider gears & metal flakes in the oil. Or it could be the PSOM going bad. Have you read this caption?

 
Steve83 said:
The sensor & its depth are probably fine. The bouncing needle is probably a result of the worn spider gears & metal flakes in the oil. Or it could be the PSOM going bad. Have you read this caption?

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I had the cover off last week so it has new fluid in it. It started back doing it as soon as i got to 45 the first time after the fluid change.
 
Did you remove the pinion gear & wash all the flakes out of its bearings, and the oil journals up there? Did you wash all the flakes out of the axle tubes, the spider gears, and their thrust washers? Did you clean the sensor & the fill plug magnets off? If you missed any of those spots, there MIGHT still be metal flakes in the oil.

But it's also possible that the fault is in the PSOM. Did you read that caption?
 
Yeah. Those sensors are pretty picky on metal chunks of flakes. They will pick up pretty minute pulses, even if they aren't from the exciter ring. I'd say that you're gonna do the right thing by getting a new sensor and cleaning out your diff really well. If you buy a new one, you might as well plan on modifying it for the correct air gap. Most of the aftermarket ones aren't quite right.
 
motorhead1024 said:
Maybe better to buy the Motorcraft sensor (DY-588) from RockAuto for $23.79.
Click to expand...

I'm sure this is a known fact to most but, I thought I would just reiterate. In my experience the actual Motorcraft sensors are wayyyy better then any aftermarket piece out there. I had replaced all my sensors over the last couple years and some with aftermarket. I am now in the process of re-replacing them with Motorcraft sensors. The MAP is the absolute worse aftermarket sensor I've found yet. Just a thought. Oh but, I have found Standard to be not too bad.
 
I had the exact same problem, i replaced the sensor, I shaved the sensor down.... My spider gears were worn as well. I refused to believe that my PSOM was going bad. Anyways, When my spider gears finally grenaded, I had the toner ring replaced when I got the new Limited Slip. After that, my speedometer was solid again.
 
If you're working in the diff. at all, do yourself a favor and replace the exciter ring (what MAF called the toner ring) while you're in there, and leave the sensor alone, aside from giving it a good cleaning. You can still get them from Ford and they're not very expensive. I've done this to both of my trucks now and still have the original sensors in there, one with about 80,000 miles and one with about 262,000 miles.

The speedometer in my Lightning was doing pretty much exactly what yours is doing. It twitched a little above 70, if I remember correctly, but as soon as I floored it, it would jump from like 60 to 100 and everywhere in between until I let off, then it would just twitch again. I figured out it wasn't the sensor's problem on the Lightning by switching it with the one in my F-150, which didn't jump in the F-150, but behaved the same as the Lightning sensor when installed in the Lightning. Also switched instrument clusters to rule out the psom. Changed the exciter ring when I later blew the diff. and now have a perfectly steady speedometer.
 
stroked93' said:
I'm sure this is a known fact to most but, I thought I would just reiterate. In my experience the actual Motorcraft sensors are wayyyy better then any aftermarket piece out there. I had replaced all my sensors over the last couple years and some with aftermarket. I am now in the process of re-replacing them with Motorcraft sensors. The MAP is the absolute worse aftermarket sensor I've found yet. Just a thought. Oh but, I have found Standard to be not too bad.
Click to expand...

Sad to say this is not the case. I work in auto parts and ordered the motorcraft, a Borg Warner and my cheap store brand. They were all made the same and had the same markings on them. I'd have to say all made by the same company. (This statement is regarding the ABS sensor) Just an fyi to anyone who cares. Borg Warner is owned by Standard Motor Products and Standard makes ALOT of Motorcrafts sensors.
 
stroked93' said:
I'm sure this is a known fact to most but, I thought I would just reiterate. In my experience the actual Motorcraft sensors are wayyyy better then any aftermarket piece out there. I had replaced all my sensors over the last couple years and some with aftermarket. I am now in the process of re-replacing them with Motorcraft sensors. The MAP is the absolute worse aftermarket sensor I've found yet. Just a thought. Oh but, I have found Standard to be not too bad.
Click to expand...

GT347SC said:
Sad to say this is not the case. I work in auto parts and ordered the motorcraft, a Borg Warner and my cheap store brand. They were all made the same and had the same markings on them. I'd have to say all made by the same company. (This statement is regarding the ABS sensor) Just an fyi to anyone who cares. Borg Warner is owned by Standard Motor Products and Standard makes ALOT of Motorcrafts sensors.
Click to expand...

Actually, you can both be right... manufacturers often supply multiple brands and retailers. But not all brands & retailers have the same quality control standards, so even though the parts in 3 different brand name boxes can all come from the same factory, it's possible for quality to vary among the 3. And burps in manufacturing lines can cause brands & retailers to change suppliers temporarily until their preferred supplier is back on line.

So all we're really left with is our confidence in a particular brand's reputation, and over the years I, like Stroked, have had some painful experiences with cheaper parts, so I prefer to play it safe and stick with Motorcraft.
 
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