Replacing Speed Sensor

[sk1er17]

Ok, after reading too many threads about 4x4 blinking lights.. .i give up.

Lets make this one easy.. anyone who has a 4x4 blinking light who thinks they need to replace a speed sensor will hopefully become enlightened:

My friends 4x4 lights blinked, got stuck in 4x4, etc.. we did the shift motor thing cause thats what fixed mine... didnt work for him.

I want to replace the rear speed sensor (or clean it)...

anyone know:

1) exact location (his is a 97 sport SOHC.. pics would be great)
2) Can we clean it or does it need to be replaced?
3) about how much do new ones cost?
4) a thread with directions on how to do it-- if not, lets make this the thread because it seems like this is a common problem out there.

-Matt

 

[blue88mustang]

I know on every mustang that I have worked on (2-88's, a 90, and my 96) the VSS is attached to the driver's side of the transmission.

I can't remember ever looking for the VSS on my Ranger and I have yet to really crawl around under the 97 Explorer.

The sensor should be on the tranny end of the speedo cable (assuming it is mechanically driven). It should be fairly easy to spot because it is just a hunk of plastic attached to the end of the speedo cable. It should just have a couple wires going to a connector that plugs into the VSS.

If I had my 97 Ford Truck Repair CD here at work, I would look it up and be more specific.

 

[sk1er17]

has anyone replaced this part before.

-If you did, did you just have the flashing lights or was your truck engaging 4x4 on its on and getting stuck in 4 wheel too?

 

[97emerald]

I cleaned the sensors on my 97. The lights were flashing and the 4wd was not working. both sensors are on the rear of the transfer case. One of the sensors is behind the shift motor so you need to remove the shift motor to remoe it. Both sensors and the shift motor were connected together by the harness, so I assume you need to replace them as an assembly. When I removed my sensors. they looked clean enough, but I wiped them of and sprayed them with electrical cleaner any way. I then unhooked the battery cable for about 5 minutes to clear any codes. That was about a month ago and all has been fine since. (Keeping my fingers crossed.)

 

[sk1er17]

did your 4x4 engage randomly though or did you just have blinking lights?

his 4x4 will engage while he's driving and he'll go around a turn and feel his wheels chatter because it goes in 4wheel low. or it'll get stuck in 4 wheel when he puts it in.

 

[dan leon]

Speed sensor on my 96 XLT a/t is in the tail housing on the drivers side. Goes where the speedo cable used to go.

 

[cantspell]

OK, this flashing light thing is driving me crazy, actully, i've noticed it only starts when on a straight for about 1km or more...
anyways, i've had a look under the truck, I hate to admit it, especially as i do most fixes (unless major) myself, but i'm not even sure where the shift motor is, actully, i'm not sure if you guys mean the transmission shift motor or transfere case shift motor?

And of coruse then i'm not sure where either of these are, or rather which one is which...Gezz, i pathethic!.

 

[Doug]

The VSS on the 97 is in the transfer case on the driver's side. it's towards the top of the t-case near the rear driveshaft, it's cylindrical and has 2 wires coming out of it. there really isnt anything there to be cleaned except the connector. i've heard of the speedo sensor breaking, remove the bolt that holds the clip for the vss on and pull the sensor there should be a gear on the end of the sensor if it isnt there that means the came off the shaft and is still in the t-case. However i havent really heard of this causing the 4wd lights to flash, it's possible your problem is electrical. I do beleive the GEM throws codes and if you take it to a ford dealership they can read the codes and hopefully tell you whats us. OR you can say screw it, stop wasting money on that garbage t-case and swap in a manual.

 

[cantspell]

Hmm, I actully work with a Ford dealer, so I think i'll do that, i hope it's not my GEM...

as for swapping in a maual T-case, nothign against it, but it's costly, and i think the auto setting on our stock T-case, is useful...but we'll see.

Anyone else have any idea's?

this seems to only happen when driving straight on a non-slippery surface.

 

[Doug]

Does it feel like the auto 4wd is engaging or otherwise acting differently than it should? Does the 4wd work? it's possible there is a loose connection some where or there could be something internally wrong with the transmission. The manual t-case swap may actually be cheaper than repairing the problem, and definantly cheaper if you have to buy a new t-case. i picked up a manual t-case for 350 and the shift linkage for 20 I also needed a driveshaft from a 95-96 explorer but i took that off of my parts truck. Definantly get them to read the codes that should help you solve the problem.

 

[checkedout]

There seems to be a little confusion here. The possible problem is the Hall effect speed sensor on the transfer case, there are two, one for the rear and one for the front (the one under the shift motor). Not the Vehicle speed sensor. I believe they are about $30 each and you can replace them by cutting and splicing or taking the connector apart, pulling the wires out and pushing the new sensor wires in. There is a thread somewhere for getting the connector apart.

 

[checkedout]

here's a description from my 96 manual

The new C-Trac transfer case (7A195) transmits torque to front wheels through an electromechanical ball ramp clutch after a predetermined delta speed between front and rear driveshafts (4602) is exceeded. These driveshaft speeds are monitored using Hall effect sensors that send signals to the new on-board Generic Electronic Module (GEM). Upon observing an exceeded delta speed, the GEM then activates the transfer case clutch coil with a varying current to minimize the delta speed.

 

[smithg3]

I noticed a problem today with the 4wd system. I have a 96 with the 2wd - 4wd Auto - 4wd Low selector switch.

I put it into 4 low to decend a rather steep, very icy hill, and noticed both the 4wd and the 4 wd low lights flashing. I then stopped, put the truck into neutral, and put it back into 4wd high. After that, I noticed the truck was fishtailing going up hills where it wouldn't before.
Now the lights do not flash either in 4wd auto or 4wd low, just the normal lights.

About two years ago I replaced both of the hall sensors on the transfer case, after the light would flash in 4wd high. It has worked flawlessly since then.

Overall, I have been happy with the truck. But with only 70,000 miles on the odo, I've had my share of problems. From the blend door malfunction at 30,000; the first failure of the 4wd system at 45,000; the mysterious antifeeze disappearances, amd the latest 4wd failure, my patience with it have just about worn out. Of course this would happen with a good snow storm on the way to the northeast.

Maybe it's time to look at the toyotas and nissans for sale.

Hope you can help.

Greg

 

[checkedout]

smithg3, the first thing I would do is change the fluid unless you've done it recently. Then I would disconnect the battery for a few minutes and test the 4wd again. If the problem returns you prolly need to clean the shift motor or replace the sensors again.

 

[smithg3]

Thanks for the quick reply. After leaving the first post, I moved the truck out of the garage, and the 4wd auto was working normally again. Since we have about 10-12 inches of snow on the way, I'll not be putting it into 4 low again just in case it decides to act up again. When the thaw comes in a couple months, I'll be sure to do the fluid change.

 

[cantspell]

Hi there, i've found the problem in my ex, which is a 98', it's was the front drive shaft speed sensor, which was actully behind the shfit motor, i took it out, cleaned it, and the problem went away for about 2 days, it's back, But it's sort of cool having 2ed and then 4wd high, serves me well.

But i still have ot get it fixed, anyone know if i can buy that from ford?I can't see where it would plug into, do you have to splice the wires?

 

[pjm]

Transer Case Speed Sensor - thanks for the info

Just wanted to say once again how valuable this forum is and how much money it can save you if you dig a little for info. I figure between diagnostic and labor charges I probably saved about $200 on this one.

I have a 96 XLT 4WD 4.0 with Control Trac.

After reading everything I could find on this site re: 4wd lights flashing, speed sensor, shift motor, I decided the problem I was having was most likely due to faulty speed sensors. Bought two new ones (front & rear) from Ford Parts Network at 25% off Ford price, about 72$ delivered for both. This was after taking a shot in the dark last fall and replacing the dash switch.

Took the connector apart just like described here, pulled the red retainer out with needle nose and did one pin at a time with a small screwdriver. Had both sensors replaced in about 1 hour and all ready to go. You do need to remove the shift motor to access the front one. (You can't find this info in your average Chilton's or Haynes!)

Result, no more flashing light. Control Trac is working the way I expect it to for the first time since I've owned the truck and just in time for winter.

thanks again everyone!