Speed Sensor rebuilt write-up
03-12-2012, 04:39 PM
#1
Registered User
Thread Starter
Join Date: Oct 2009
Location: San Jose, CA
Posts: 93
Likes: 0
Received 0 Likes
on
0 Posts
Speed Sensor rebuilt write-up
A lotta folks (including me) with the 4x4 are having trouble with the speed sensor (located off the transfer case) failing causing the dreaded "speedometer bounce" or the speedometer fails completely. This is for '92-'95 4WD Runners with the speed sensor, not the speedometer cable.
My original sensor (my truck was built in 11/'91) started to fail in 2009 so I went to the local junkyard and got a replacement from a '95. Three years and several thousand miles later, that one started to fail as well, causing the speedo bounce, irratic shifting, and the cruise control wouldn't work. A buddy of mine told me he'd replaced his sensor 3 times before he just broke down and bought a new one for $150.
What you'll need: Small flat-bladed screwdriver, 12mm socket & rachet (maybe a small extension), engine degreaser and some form-a-gasket.
I didn't want to spend that kinda money so I thought I would take mine apart to see if I could rebuild it. I kept my original sensor just in case I needed it and I'm glad I did.
Here's how it went:
1. I took a 12mm socket and small flat-bladed screwdriver under my truck's passenger side and used the screwdriver to unclip the wiring from the sensor. Then I used the 12mm socket to unscrew the sensor from the xfer case. It came out easily (it was loose) and was coated in tranny fluid.
2. I took the sensor to the bench and unscrewed the black cap where the magnets are (I've done this before). What I've found in previous experiences is that the magnet gets covered with tranny fluid which then makes the small square sensor (housed in the black plastic piece) unable to read the magnet (housed in the body of the sensor). I've cleaned the tranny fluid off the magnet a few times only to have the problem reoccur in after a couple of miles. When the truck sits overnight the tranny fluid seems to always make its way back to the magnet. Therefore I believe I have a small hole or leak from where the shaft sits to where the magnet is.
** Do yourself a favor and use needle-nosed pliers to loosen those screws before attempting a screwdriver. They are on there pretty tight and you'll strip them if you don't use pliers to loosen the screws first (ask me how I know!)
3. Remove the locking clip from the sensor so that the shaft slides out easily. The shaft has groves in it for what I assume is to let tranny fluid lubricate it while it spins in the sensor housing. My theory is that the tranny fluid makes its way down the shaft and somehow leakes behind the magnet and eventually covers the magnet. I found that if you pull & push the shaft in & out of the housing you can actually hear a small pinhole leak (you can hear air escaping...but you have to listen carefully).
4. Soak the shaft, housing, and magnet with engine degreaser. This should remove any tranny fluid from where it shouldn't be. Spin the magnet by hand to get the degreaser underneath the magnet. Let it dry for a couple hours.
5. Looking down the housing where the shaft usually is, you can see that there is no gasket between the inside bottom of the housing and the outside where the magnet sits. My hypothesis is that fluid leaks through at this point and eventually covers the magnet. I used a very small bit of black form-a-gasket to try to stop the leak. Then I flipped the housing over and used the small flat-bladed screwdriver and a hammer to GENTLY pound on the center of the magnet to ensure it was up against the housing tightly. Don't hit it too hard or you'll break the magnet (ask me how I know.).
6. While I had both sensors handy, I decided to compare them and see if I could find any differences due to wear that might lead me to believe that my original sensor (with about 125K miles on it) was different than the junkyard sensor (from a Runner with over 200K) and that might give me a clue as to how these things wear. I was shocked to see that the speed sensor shafts were different sizes! The junkyard shaft was slightly shorter than my original shaft.
7. Make sure the magnet is tight up against the housing. You can test this because the magnet will be much more difficult to turn by hand. Replace the shaft back into the sensor housing and make sure the whole assembly is much more difficult to turn. Also make sure you don't hear anymore air from the pinhole leak. If this is the case then you've probably solved your tranny fluid leak.
8. Bend the locking clip a little so it fits tightly. Replace the black plastic piece (3 screws) and reinstall on your xfer case. If you did it right, it should be rather difficult to reinstall due to the clip being bent. This should keep the sensor in place a little better.
I did this and took my Runner out and it worked right away. After several days I haven't had any more problems. The key was making sure the tranny fluid doesn't leak through the housing onto the magnet. It seems like a lot of hassle but it's only a 45-minute job and I saved $150.
You can view my photos of the disassembled speed sensor here: http://www.flickr.com/photos/4606645...n/photostream/
Good luck!
My original sensor (my truck was built in 11/'91) started to fail in 2009 so I went to the local junkyard and got a replacement from a '95. Three years and several thousand miles later, that one started to fail as well, causing the speedo bounce, irratic shifting, and the cruise control wouldn't work. A buddy of mine told me he'd replaced his sensor 3 times before he just broke down and bought a new one for $150.
What you'll need: Small flat-bladed screwdriver, 12mm socket & rachet (maybe a small extension), engine degreaser and some form-a-gasket.
I didn't want to spend that kinda money so I thought I would take mine apart to see if I could rebuild it. I kept my original sensor just in case I needed it and I'm glad I did.
Here's how it went:
1. I took a 12mm socket and small flat-bladed screwdriver under my truck's passenger side and used the screwdriver to unclip the wiring from the sensor. Then I used the 12mm socket to unscrew the sensor from the xfer case. It came out easily (it was loose) and was coated in tranny fluid.
2. I took the sensor to the bench and unscrewed the black cap where the magnets are (I've done this before). What I've found in previous experiences is that the magnet gets covered with tranny fluid which then makes the small square sensor (housed in the black plastic piece) unable to read the magnet (housed in the body of the sensor). I've cleaned the tranny fluid off the magnet a few times only to have the problem reoccur in after a couple of miles. When the truck sits overnight the tranny fluid seems to always make its way back to the magnet. Therefore I believe I have a small hole or leak from where the shaft sits to where the magnet is.
** Do yourself a favor and use needle-nosed pliers to loosen those screws before attempting a screwdriver. They are on there pretty tight and you'll strip them if you don't use pliers to loosen the screws first (ask me how I know!)
3. Remove the locking clip from the sensor so that the shaft slides out easily. The shaft has groves in it for what I assume is to let tranny fluid lubricate it while it spins in the sensor housing. My theory is that the tranny fluid makes its way down the shaft and somehow leakes behind the magnet and eventually covers the magnet. I found that if you pull & push the shaft in & out of the housing you can actually hear a small pinhole leak (you can hear air escaping...but you have to listen carefully).
4. Soak the shaft, housing, and magnet with engine degreaser. This should remove any tranny fluid from where it shouldn't be. Spin the magnet by hand to get the degreaser underneath the magnet. Let it dry for a couple hours.
5. Looking down the housing where the shaft usually is, you can see that there is no gasket between the inside bottom of the housing and the outside where the magnet sits. My hypothesis is that fluid leaks through at this point and eventually covers the magnet. I used a very small bit of black form-a-gasket to try to stop the leak. Then I flipped the housing over and used the small flat-bladed screwdriver and a hammer to GENTLY pound on the center of the magnet to ensure it was up against the housing tightly. Don't hit it too hard or you'll break the magnet (ask me how I know.).
6. While I had both sensors handy, I decided to compare them and see if I could find any differences due to wear that might lead me to believe that my original sensor (with about 125K miles on it) was different than the junkyard sensor (from a Runner with over 200K) and that might give me a clue as to how these things wear. I was shocked to see that the speed sensor shafts were different sizes! The junkyard shaft was slightly shorter than my original shaft.
7. Make sure the magnet is tight up against the housing. You can test this because the magnet will be much more difficult to turn by hand. Replace the shaft back into the sensor housing and make sure the whole assembly is much more difficult to turn. Also make sure you don't hear anymore air from the pinhole leak. If this is the case then you've probably solved your tranny fluid leak.
8. Bend the locking clip a little so it fits tightly. Replace the black plastic piece (3 screws) and reinstall on your xfer case. If you did it right, it should be rather difficult to reinstall due to the clip being bent. This should keep the sensor in place a little better.
I did this and took my Runner out and it worked right away. After several days I haven't had any more problems. The key was making sure the tranny fluid doesn't leak through the housing onto the magnet. It seems like a lot of hassle but it's only a 45-minute job and I saved $150.
You can view my photos of the disassembled speed sensor here: http://www.flickr.com/photos/4606645...n/photostream/
Good luck!
Last edited by GO_BLUE!; 03-12-2012 at 05:09 PM.
03-12-2012, 08:30 PM
#4
Registered User
Thread Starter
Join Date: Oct 2009
Location: San Jose, CA
Posts: 93
Likes: 0
Received 0 Likes
on
0 Posts
sorry 'bout that. I posted some pictures here: http://www.flickr.com/photos/4606645...n/photostream/
07-26-2012, 06:06 PM
#6
Registered User
Join Date: Jul 2012
Posts: 8
Likes: 0
Received 0 Likes
on
0 Posts
My sensor went out too. Speedometer, Odometer went out and after 100 miles driving long distance, my check engine light and O/D light came on. Checked codes and both concluded the problem was VSS.
So, I too tried https://www.yotatech.com/forums/f116...ite-up-250730/ to no avail. Figured I'd buy one from CarQuest, installed it, and my Speedometer/Odomter still don't work.
I haven't reset ECU, but didn't think that would matter. I also haven't checked the harness prongs to see if it's a wiring/relay issue.
I was wondering if anyone had other steps I should try, since I already dropped $230 on a new part. What has been your solution Helmster1363
So, I too tried https://www.yotatech.com/forums/f116...ite-up-250730/ to no avail. Figured I'd buy one from CarQuest, installed it, and my Speedometer/Odomter still don't work.
I haven't reset ECU, but didn't think that would matter. I also haven't checked the harness prongs to see if it's a wiring/relay issue.
I was wondering if anyone had other steps I should try, since I already dropped $230 on a new part. What has been your solution Helmster1363
Thread
Thread Starter
Forum
Replies
Last Post
montanatruck
86-95 Trucks & 4Runners
15
02-26-2017 07:07 AM
