I am replacing the rear differential VSS (Vehicle speed sensor/ABS sensor) and I have a question regarding the new one that I ordered from partsgeek which clearly stated it was for a 1998 F150 XLT 2WD 4.2L V6. The new one, pic attached, has this black cap looking thing on the bottom of it (underneath the orange o-ring). When I took out the old one, it doesn't. The old one looks more like a magnet/metal. I stuck my finger into the pumpkin to feel if the black cap possibly broke off as I was pulling the sensor out, but my finger instantly gets covered in diff. oil and I can feel what feels like gears of the differential. Does this black cap have to be taken off of the new sensor before replacing it? I'm not sure - any threads I've found with pictures of new sensors just shows the sensors with the black "caps" on it. I called a ford dealership and the guy asked if it was an OEM ford part - I said no, and so he asked a technician and he said he never heard of a "black cap" on them that it probably has to come off. Any idea guys? Hopefully someone is reading the forums today as it'll be dark soon and I want to get this sensor put back in.

Thanks in advance!

 

Update: Ok so I talked to my buddy who's a mechanic and he said they just look different b/c this one is aftermarket. So for anyone searching/wondering for the same question as mine, that is the answer. Just put the new sensor in as-is.

Now, I ran into a problem. I put the new sensor in, torqued it down, thought all was good. Go to run the truck to make sure I'm not having any problems...well the braking feels better however now the speedometer quit working. I know that this sensor also controls the input to the speedo. Anyone have any ideas what to do? (btw, I unplugged the battery while installing the new sensor)

 

To my knowledge, that sensor has nothing to do with the speedo. It is just an ABS sensor. I replaced mine a month ago, my new one looked identical to your picture there and worked fine. The old sensor had been not working for several months, tripping the ABS light on the dash, and the speedo was never affected.

 

BTW The 97s and 98s had a gear driven speedo system that is in the transmission

 

Right, the 4x4's do. Not sure about the 2wd's ? I haven't had to change mine yet. But it looks exactly like that one in the picture. On the 98, I would make sure the wires aren't broke inside the insulation. They can break easy and are hard to determine without a multi-meter. So you might want to follow testing procedure for that circuit.

 

Thanks for your help guys. I read on the forums that someone else had this problem after replacing their sensor on top of the diff (97-03's) but now I can't find that thread again, been reading every single posted thread on this subject all night lol Gained a load of information & knowledge though.

The whole reason why I am replacing the sensor is I'm currently fixing up this truck to drive - my father owned it since it was brand new and put 144k miles on it. He stopped driving it and bought an 04 F150 4x4 as he no longer felt safe in this one because of it "acting up" I suppose. He claimed for a while the ABS sensor kept coming on and off and the back brakes just "never felt right, like they are locking up or something every so often." He replaced the rear drums and shoes with brand new everything and it was still doing it, according to him. That is when I suggested if he bled his brakes, did he do it completely or is it possible he still has air in the system? He claims he bled it completely. I then asked if he looked into the ABS and he said "no, not yet." So changing this ABS sensor is me just basically crossing my fingers that it will fix the problem and is one of the cheapest things to start with. < $10 shipped from partsgeek. (btw, the ABS light has not been on at all since I've started working on the truck, however it needs new plates so hasn't been on the road in over a year so it's hard to say. Driving it down my long driveway which is a hill, every so often it did feel like the rear brakes were acting up, I wouldn't so much say "locking" up however.)

The kicker that gets me, as people keep saying that this is strictly an ABS sensor and does not provide input to the speedometer. Well, before I changed the sensor, the speedometer worked perfectly fine. Which makes me want to rule out the wire problem as it was working just 2 seconds beforehand. In the morning I'm going to plug the old sensor back in and just see if the speedometer starts to work again.

I did unplug the battery during the entire time I was under the truck changing this sensor - but if anything that should have reset the entire system. Not forced the speedo to stop working/receiving a signal. There is no CEL or codes as far as I can tell but I'll rescan it in the morning (just with my OBD II)

Just for information:
Before changing the sensor I did check F13 and F15 in the fuse panel, and also the 20A fuse in the Power distrib. box (engine bay). All of them are in perfect condition. I just wanted to rule out the fuses before swapping sensors.

 

The brakes get goofy in these trucks when the rubber brake lines break down inside. This cause fluid flow problems. Ford rubbers should be replaced, specially if their ancient. I know my brakes were far from being normal at one time. I replaced everything but the rubbers. It wasn't until I replaced all the rubber lines that I got that stop like new feeling back. I mean , I went thru EVERYTHING else first, Calipers, rear wheel cylinders, master cylinder, etc etc..

You have One rubber brake line in the rear and two in front. Rock auto sells replacements.

 

jbrew, I'm sorry, but what do you mean by Ford rubbers? Rubber brake lines?

 

Yea, that's what I said, -right ? Okay , just checked, that is what I said lol.

 

so tomorrow I'm going to test the sensor wires with my meter. What is a normal working standard? If the wires are fine, and if plugging in the old sensor allows the speedo to work again, my plan is to run to the dealership and get an oem sensor. while there, should i also consider getting a new VSS sensor that's located on the tranny? and ask about the tooth gear? I think I read there is one on the end of the tranny VSS?

and you think I'd definitely benefit from changing the rubber brake lines...