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Old 08-09-2021, 07:50 PM   #1
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Default DIY: How to Replace the ABS Sensor on Late-Model Hardbodies


The ABS light on my dash came on a couple of months ago, and after doing the diagnostic procedure from the repair manual, I concluded that the ABS speed sensor had failed.

Now, the ABS sensor on the Hardbody is something special: there's only one sensor, and it's not at the wheels. It's on the rear differential, near where the pinion mates to the prop shaft. I couldn't find a lot of information online about it, and it took me a couple nights' research to figure out what I needed to do to replace it without taking the whole diff apart, so I'm paying it back here on IN.

The sensor is expensive and hard to find, and mine cost me about $500 and several hours of time spent searching. I chose to get a nice one from NTK; maybe you can find one cheaper. Here's where I got mine.

The sensor is also extraordinarily tough to replace: this ain't no half-hour wheel sensor job. It's a solid metal ring, integrated into the rear diff, behind the companion flange/yoke where the prop shaft bolts on to the diff, and notably behind the pinion nut. This means we have to remove the pinion nut to get at the sensor.

As the red warning at the top states, this guide is only for the H223B rear axle. This rear axle has no crush fittings on the pinion, which allows us to take off the pinion nut without replacing any crush washer/sleeve inside the diff, and thereby do this whole job with the diff still on the truck. This is not the case for the other typical rear axle on 90s Hardbodies, the H190A axle; that one has a crush sleeve which must be replaced every time the pinion nut is loosened, requiring full disassembly of the diff. If you're not sure which axle you have, check your door card.

To do this job, you will definitely need:
  • 14mm and 17mm wrenches and sockets
  • 30mm (may also be 31mm or 32mm if you're unlucky, by what I've read) impact socket; deeper is better
  • Paint pen, or some other way to make permanent marks
  • Breaker bar
  • Deadblow mallet
  • Gear oil (75W90)
  • Oil drain pan

I also highly recommend:
  • Impact wrench
  • A 3-4" gear puller
  • Ballpeen hammer
  • Chisel, small metal pry tools
  • 80 grit sandpaper
  • Penetrating oil (PB Blaster)

You may also appreciate:
  • Big torque wrench (200 ft-lbs at least, ideally 300)
  • Red Loctite
  • Blue or black RTV
  • Inch-pounds torque wrench
  • Specialty "drive pinion flange wrench", Nissan tool no. KV38104700 / Kent-Moore no. J34311
  • Heat gun

Now we're ready to begin!

Step 0

This job will result in the loss of about a quart of your diff's gear oil; if you haven't changed it in a few years, you might as well drain it all before you begin. The H223B diff takes a total of 2.8 quarts of gear oil.

Step 1

Jack the rear of the truck up, put it on some stands. Loosen and remove the four bolts holding the rear prop shaft to the rear diff flange: they're 17mm bolts with 17mm nuts on the back. Leave just one bolt through and loosen the two bolts on the center support bearing (see red circles in image below) to get enough play in the prop shaft that you can slip it off the diff and set it to the side.

Once you get the prop shaft separated from the diff, you should be looking at something like this (bonus: note the huge pinion flange wrench, bottom-right):

Now is a good time to release your parking brake and give the flange a gentle spin and feel how easy it is to turn. Do the same thing with one of your wheels and see how easily the whole assembly turns. Remember this feeling for reassembly later.

Step 2

Next, use your paint pen to mark a line on the threaded end of the pinion rod and the pinion nut. Here's a picture to show what I mean:

It's a bit hard to see in the picture, but there's blue paint on the inside of the flange too (it can be seen near the bottom of the picture); this will make sure that the flange goes back in the same place, for bonus points. I don't think the flange position really matters (the only thing I can think that might go wrong is that the balance of the prop shaft may be affected a little), but it's nice to put things back in the same way they came apart. What is important is that you mark the pinion nut's position; this is possibly the most sensitive part of the whole job, so do it right!

Measure the pinion nut with some calipers, before you buy the wrong kind of socket; it's probably 30mm, but I've read that it might be 31 or 32 instead.

Now it's time to take off the pinion nut. If you have the optional pinion flange wrench, put it on the flange. (If not, then just set the parking brake to prevent the diff from spinning.) Then put your big 30mm socket through the hole in the center of the flange wrench, hold tight to the flange wrench and start turning that socket! A high-torque impact wrench really helps here, but you could conceivably do it with a big breaker bar.

Here's a picture of the pinion nut off:

Step 3

Next, get your drip pan and put it under the diff. We're about to get messy. If you don't have a gear puller, then a big mallet and some brute force 'n' ignorance should get it off, though I really recommend the puller... it makes it so much easier. (You can get a cheap one for less than $20.) Fit your gear puller over the flange and start pullin'!

You may have to give the flange a final tug to get it off, once it's free of the pinion splines. As soon as you do, about a quart of diff fluid will come spilling out (assuming you didn't already drain it).

Step 4

Once the fluid has mostly stopped dripping, unplug the sensor and remove the three bolts holding it on. If your sensor is anything like mine, then it will not come off without a fight! I couldn't tell for sure, but mine appeared to have been glued onto the diff, in addition to being bolted on. It took a lot of hammering with a chisel and then a lot of prying to get mine off, and I did some damage to the sensor housing just to get it off:

If I were to do it again, I'd try a heat gun. That might have made it a lot easier.

Once you get the sensor off, you'll want to clean up the mating surface with some 80-grit sandpaper, especially if yours was maybe-glued like mine. Don't worry about getting it perfectly clean-looking, just remove most of the rough stuff. Wipe it clean, then inspect the rubber seal for dryness or cracking (mine was still nice and supple, which was nice for a change).

Step 5

As they say, "assembly is the reverse of disassembly". I stopped taking pictures at this point, so forgive the following wall of text.

Slide the new sensor on. Optionally, you can first apply a little bit of RTV where you sanded; I skipped it since there's already a rubber seal internally, and the sensor is held on very tight by the pinion nut. I gave it about a dozen gentle taps with my deadblow mallet, in a circular pattern to make sure it went on straight. Put in the three bolts that hold it in place, torquing to a gentle 25-30 ft-lbs. Nissan used grade 7 bolts to hold the sensor on and I broke one as I was removing it (IMO, grade 8 bolts wouldn't have broken), so I also chose to replace all three bolts holding the sensor. You definitely don't need to, but mine were quite dirty and rusty, so I went with clean, stronger bolts.

Don't forget to plug the sensor cable in, too!

Step 6

Push the pinion flange back on, again tapping it with the deadblow mallet to get it most of the way on. For bonus points, line up the paint marks you made on the pinion flange with the pinion bolt, so the teeth spline to the same teeth as before (like I said earlier, this doesn't really matter, but it's a nice-to-do). The pinion nut will help squeeze the flange on all the way, but try to get it as far on as you can with your hammer (gently!).

Step 7

Optionally apply a little bit of red Loctite to the inside of the pinion nut threads; this isn't necessary but may give you some peace of mind. Spin the pinion nut on with your fingers as far as you can, then set your big torque wrench to 250 ft-lbs, fit back on the pinion flange wrench if you've got it (otherwise, set the parking brake), and start tightening. If you don't have a big torque wrench, then a big breaker bar will do. It's more important here that you get the pinion nut back in the exact place it was before (you did mark it with paint, right?) than it is to get a full 250 ft-lbs of torque on it, especially if your diff is original and has gone many hundreds of thousands of miles: it's settled into a way of being that's best not interfered with, short of a full rebuild. Whatever you do, do not over-torque it, lest your diff burn itself up due to being too tight. Resist the urge to use your impact; this is really best done by hand.

After you've put the pinion nut back on, release the parking brake and give one of your wheels a gentle spin. Ensure that it still turns as easily as it did before disassembly. If you've got an inch-pounds torque wrench, use it to spin the diff and make sure it only takes between 5-20 inch-pounds of force to turn the diff.

Step 8

Reattach the driveshaft (the bolts only need about 40 ft-lbs of torque, no need to overdo it) and don't forget to tighten down your center support bearing if you loosened it.

Refill your diff with fluid, then take it for a test drive! Hopefully your ABS works again now.

Last edited by suntenti; 08-10-2021 at 04:10 PM. Reason: Replace images with links from imgur
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Old 08-10-2021, 05:54 AM   #2
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Good info. Got pics? Looks like the post is spaced to include some, but not seeing any.

And yeah, this style of sensor sucks. It was also on WD21 Pathfinders. The other style with separate sensor held by a single bolt was the way to go. It did appear on other Hardbodies with H233B (such as the V6 2WDs), though, and eventually was the style on Frontiers and Xterras with the H233B and H190A. The harnesses were even the same, although the sensor changed a little.
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Old 08-10-2021, 03:52 PM   #3
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Originally Posted by Hawairish View Post
Good info. Got pics? Looks like the post is spaced to include some, but not seeing any.

Hmm, I uploaded the pictures to an IN album (https://www.infamousnissan.com/forum...p?albumid=3218), like the "how to post pictures" thread said to do, but they only show in the post for me when I'm logged in, despite the fact that the album is marked as "public"... guess public ain't really public. Let me upload them to Imgur instead.

edit: uploaded and changed. Pics should appear now.

Last edited by suntenti; 08-10-2021 at 04:01 PM.
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Old 08-10-2021, 04:41 PM   #4
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Looks good!
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Old 08-10-2021, 05:22 PM   #5
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Good writeup suntenti! ...and a bunch of great info! Thanks!
. . . Factory Service Manuals: https://www.nicoclub.com/FSM/Hardbody/
Originally Posted by Deerhurst
What he is saying is the aerodynamics of a D21 is a brick in the wind.
Probably at least as bad as a Jeep so worse than a cow.
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