Help with VSS

14492 Views 38 Replies 16 Participants Last post by TravisITGuy, Jun 24, 2007

wasp1971

Discussion Starter · Apr 18, 2005

Hey guys. I did a search and still need help. I've got a 93 that the speedo is fluxing on. I recently had gears put in so the shop just replaced my exciter ring and that didn't fix it. And I've already replaced the rear ABS sensor on top of the rear diff housing. So I bought a VSS(vehicle speed sensor) from advance today and can't find where to plug it in. Where is this dang thing????

21 - 39 of 39 Posts

bigric

· #21 · Apr 21, 2005

Ask for the ABS sensor. I dunno if they'll have it, but if they don't, it's less than $20 from the dealer. I think I paid about $12 for mine.

Shadofax

· #22 · Apr 21, 2005

bigric said:
Ask for the ABS sensor. I dunno if they'll have it, but if they don't, it's less than $20 from the dealer. I think I paid about $12 for mine.

$24 and some change at Ford. Here is the part #
F85Z-2L373-AC

The parts guys at ford will likely refer to this as the rear diff. ABS sensor. Though we all now know it actually serves ABS and VSS requirements.

Steve83

· #23 · Apr 22, 2005

MustangGT221 said:
I disagree,...according to Ford, that's incorrect.

Some Ford documents refer to it as the VSS because of its function: yes. But the original technical & parts references called it the ABS sensor because that's what it ORIGINALLY was, and they kept using that name, despite other names being added. (Are you looking in an EVTM?)

MustangGT221 said:
In regards to the plastic gear driven "sensor" for the cable operated speedometer of the 87-91's ...how can it be called a VSS (vehicle speed sensor)...when I think of sensor I think of electronic stuff, that ain't electrontic its just a plastic R+P.

Pre-85 & '85-86 non-cruise had nothing but 2 plastic gears - that's not a VSS. The one Bob's photo shows is an electronic VSS because, in addition to holding the gears in place, it also has 6 magnets passing a coil to produce a speed-relative pulse for the cruise & early E4ODs to use. That's what the wires are there for.

MustangGT221 said:
it's just different words to describe the same thing, ...

...which can be VERY confusing for people trying to learn about their trucks. But if we ALL use unique terms for specific parts, we'll make it easier for EVERYONE to understand. So how about we all call the sensor in the middle of the rear axle the ABS, the one(s) on the trans/t-case tailhousing the VSS, the ones at the hubs WSS (Wheel Speed Sensor), & the one in the middle of the trans OSS (Output Shaft Sensor)? :shrug Those are the names Ford used back when they were building these trucks. Current documentation probably varies widely.

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MikE2

· #24 · Apr 22, 2005

Steve sometimes you just get too technical.

Bronco Rob

· #25 · Apr 22, 2005

Steve83 said:
The one Bob's photo shows is an electronic VSS because, in addition to holding the gears in place, it also has 6 magnets passing a coil to produce a speed-relative pulse for the cruise & early E4ODs to use. That's what the wires are there for.

Uhm....this is the ABS/VSS sensor....how hard is it to change this thing out? Am i going to have to worry about the gears it's holding dropping out when i remove it??

MustangGT221

· #26 · Apr 22, 2005

OK steve, I forgot about that electrical plug for the cruise....my mistake. I had tunnel vision on that. I agree on calling it the same thing, I was just trying to mention what my book said. I hate how they use different names for the same thing too.

bigric said:
It's the sensor for the rear ABS, which just so happens to also function as a VSS on these trucks.

I tried to say this several times earlier in this thread, apparently no one was getting it until bigric said this, apparently I wasn't wording it right.

Bronco Rob said:
Uhm....this is the ABS/VSS sensor....how hard is it to change this thing out? Am i going to have to worry about the gears it's holding dropping out when i remove it??

All that is is just a sensor ontop of the rear diff. It's held in by 1 bolt, so all you do is remove the electrical connector, unbolt it, and pull it out. It's just a magnet, no gears on it to worry about.

The gears your worring about, are on the cable operated speedo setup pictured previously in this thread. You don't have that because you have a 93'.

It does help control how the tranny shifts, because part of the information the tranny needs, is vehicle speed.

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Shadofax

· #27 · Apr 22, 2005

Bronco Rob said:
Uhm....this is the ABS/VSS sensor....how hard is it to change this thing out? Am i going to have to worry about the gears it's holding dropping out when i remove it??

Extremely easy. 1 bolt holds it. clean around the area first so crap does't fall into your diff housing through the hole. be careful with it, the sensor housing is just plastic, and the magnet inside has wires that run to it. basically once you pull it, you will see it has a little rubber o ring for sealing (and it fits snugly, so if you've never removed it, it might feel like it does not want to come out at first). You can look down into your diff and see that it sits just right on top of a "toner" ring which turns with the carrier. The magnet at the tip is very close to this toothed ring, and the interuption of the magnetic field by the teeth as they pass close to the magnet creates a variable signal, which can be "interpreted" into a speed reference for the computer, tranny, etc.

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Bronco Rob

· #28 · Apr 23, 2005

Sweet!

This sensor also has something to do with the 4lo option too IIRC. Going to order mine up.

Thanks for the help guys i apprecaite it, going to change the diffy fluid while i am at it....

Steve83

· #29 · Apr 23, 2005

Rob
You're confusing them again. Your '93 doesn't have a VSS (in the t-case with plastic gears). It ONLY has an ABS (in the rear diff). The ABS has almost nothing to do with 4L.

As you can see from these EVTM diagrams, the t-case OSS is integrated into the t-case wiring harness, in the lower R corner.

.

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Bronco Rob

· #30 · Apr 23, 2005

Steve83 said:
Rob
You're confusing them again. Your '93 doesn't have a VSS (in the t-case with plastic gears). It ONLY has an ABS (in the rear diff). The ABS has almost nothing to do with 4L.

As you can see from these EVTM diagrams, the t-case OSS is integrated into the t-case wiring harness, in the lower R corner.
.

Thats not my biggest worry right now, i will troubleshoot the 4 low soon, i think i know where the problem is in that. I got 4hi so i am happy.

My biggest worry is that i have a sporratic hard shift, and the tranny seems to hesitate to shift when i get on the highway. I am going to post (start a new thread) on it, along with a few other things, i will ask about the OSS sensor there.

MustangGT221

· #31 · Apr 24, 2005

Steve, I duno, I think you're confusing him by saying it's just an ABS sensor. On his truck, I believe the transfer case gets the signal from that sensor (because there isn't any other sensor for speed), and it will affect automatic tranny shifts, as well as the speed limiter. I think I'm going to have to sit the rest of this one out and let ya'll work it out.

Steve83

· #32 · Apr 24, 2005

Rob
Don't worry about the OSS - concentrate on the ABS sensor. If it's OK, then you probably have internal transmission problems.

MustangGT221
I'm not saying it's "just an ABS sensor" - I'm saying it's CALLED an ABS sensor, and it's the only thing on his truck that senses speed (for the speedo, EEC, trans, ABS, & cruise). He has no VSS.

The t-case has its own internal OSS that's used ONLY for t-case shifting.

bronco1

· #33 · Apr 24, 2005

Depending on the year(1992 +) it's called a RABS sensor,a DSS(diff speed sensor),Rear axle sensor.At work (Ford dealership),we ask for a rear diff speed sensor.If we want the one on the transmission or transfercase(1991 and older),we ask for the vehicle speed sensor at the trans or tranfercase.In 1993 the sensor is called a DSS,most commonly known as the RABS(rear ABS sensor)because the signal it generates goes to the ABS module first(where the signal is altered to a form that the PSOM will understand)then to the PSOM and what ever else requires a speed signal.

Steve83

· #34 · Apr 25, 2005

bronco1 said:
...the signal it generates goes to the ABS module first(where the signal is altered to a form that the PSOM will understand)...

The PSOM understands that signal fine - I have it running direct on my truck. It's the PSOM that modifies it to a standard 8000 pulses per mile (using the conversion constant) for everything else, except the ABS system. AFAIK, the RABS or 4WABS module just passes the signal thru.

Broncodell

· #35 · May 21, 2007

I figured there wern't alot of pics of this on here, and I just did it tonight, so here ya go.

this is with the old one out and the new one in.

The other night, it started to shift way late and jolt really bad. Speedo and odometer stopped working and the overdrive "off" light on the shift lever started blinking. I tried just taking the sensor out and cleaning it off. That didn't work so a quick run down to the parts store and $15 later, back to normal. :chili:

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bigblockbuggy

· #36 · May 21, 2007

Ask for one, if they tell you it doesn't exist, or the one they bring does not match the one that you pulled from your diff and have in your hand, ask for the other. I have personally asked for and purchased a VSS for a '93 F150 at autozone, it was the proper sensor for the rear diff. Whether it is used to for ABS, cruise, or speedo output, really makes no difference to the sensor, and IMO should not change it's name. After all, whether it is being used for any of the above reasons, it is still measuring rotational speed. The sensors typically send a square wave DC or AC sine wave signal. The electronics interpreting the signal count the "pulses", i.e. how many times the voltage passes the 0 volt threshold, and interprets that as a certain speed that has a direct relationship to the number of teeth on the relucter ring (variable reluctance sensor, what the VSS in question is), number of magnets on a flying magnet wheel (hall effect), and number of shutters in a optical wheel (optical sensor).

To muddy the waters even more. all of these types of sensors can be used to determine exactly where something is in a rotation by removing one or more teeth from the reluctor, closing one or more shutter in a optical wheel, and removing one or more magnets in a flying magnet wheel. This is how newer ecm's get their crank and cam position signals.

Anyhow, the basic principles are all the same, and they are all used for measuring rotational speed. What the dealer or auto parts store wants to call them is another story all together though...

As for the T-case VSS, the one on my '89 bronco w/ electric shift BK1356 was used for the 4x4 shift computer, and was a different critter all together. It was driven like a normal speedo, with set of speedo gears, and had what looked like a small motor with a wiring harness instead of a cable... I always wondered why ford had to have 3 speed sensing devices in those trucks...

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TravisITGuy

· #37 · Jun 23, 2007

wheel speed sensor, where is this located. would it possibly cause the abs light to stay on and the speedometer to not function? I have already changed out the rear sensor on top of the diff

Shadofax

· #38 · Jun 24, 2007

kemicalburns said:
wheel speed sensor, where is this located. would it possibly cause the abs light to stay on and the speedometer to not function? I have already changed out the rear sensor on top of the diff

in addition to the rear sensor there are 2 sensors at each front wheel. but, I don't think these would have anything to do with the speedo. Are you sure everything is ok with the new rear sensor? have you opened the rear diff cover to inspect the toner ring?

TravisITGuy

· #39 · Jun 24, 2007

no i have not inspected the tone ring yet. that is next on the list

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