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I'm honestly afraid of what y'all are going to teach me in this post, smh...
This weekend I replaced the RH rear bearing, carrier and axle on BooBerry. The PO, for a temp fix, had placed a carrier and axle from what I think was a 1981 928 that was made (I think) before ABS was an option. It sucked, the bearing moaned, it was all bad in everyway so I parked her a while back until I could get the parts and do the work.
I have an axle and carrier if anyone needs. PM me and we can talk.
The parts I got, carrier and axle are ABS type, and fit together nicely. Having the carrier first and the axle second I placed the carrier two weeks before finding and receiving the axle. Thru the axle in just a few minutes. Then, I went to place an ABS sensor that I got from (top secret information, lol) and BAM it only seemed to press about 2/3 of the way in before bottoming out on the teeth for the ABS. ****!
More, the teeth are different. Original have smaller more closely spaced teeth... What explains this? Will the tooth intervals and numbers matter to the sensor?
I will send along some photos of the sensors but they are exactly the same size and barrel.
What to do??? I've been thinking of machining a spacer of some sort to make up the 1/3 difference...? Any suggestions?
Here's some pictures - and yup, I've got some cleaning to do.
Driver's LH side... Small teeth deeper recess Passenger RH side,,, new set,,, larger teeth shallower recess.
I think you might be fooked. Looks like you got a 1986.5+ axle. That looks just like the axles on my 1986.5 and on the 1988 S4 donor rear suspension I am using.
To my understanding, early ABS, 1985-86, used more/smaller teeth on the reluctor, a different speed sensor, and a different ABS computer than the later 1986.5.
Search ABS here on Rennlist and go from there. I don't think your carrier is any different, though. I could be wrong.
I think you might be fooked. Looks like you got a 1986.5+ axle. That looks just like the axles on my 1986.5 and on the 1988 S4 donor rear suspension I am using.
To my understanding, early ABS, 1985-86, used more/smaller teeth on the reluctor, a different speed sensor, and a different ABS computer than the later 1986.5.
Search ABS here on Rennlist and go from there. I don't think your carrier is any different, though. I could be wrong.
I just dug through the 1986 Technical Manual and the 928 WSM. Major changes were made to the ABS system for model year 1986, NOT 1986.5. So, your 1986 SHOULD have all the later gear.
Please go to WSM Volume 4, Section 45, and read up on the ABS system.
The 1984-85 axles had 90 teeth and used a sensor with a rectangular top and a round plug. The 1986 and newer axles had 45 teeth and used a sensor with a round top and an oval shaped plug.
Post photos of your sensors and we will go from there.
Also, looking closely at your photos, I think I see a discrepancy in the sensor mounting bores.
Passenger's side with the wide teeth on the axle, that hole looks like the one in my 1986.5, the counter bore for the O-ring at the top of the sensor is relatively shallow.
Driver's side with the narrow teeth on the axle, that hole looks like the counter bore is deeper. This could be an optical illusion I am seeing.
I have looked in PET, and have noted different part numbers for pre 1986 and post 1986 rear wheel carriers. I don't know what the difference is in them. Could be related to ABS wheel sensor mounting.
I trust Roger Tyson. What he is saying here is that early 1986 928s had the same ABS set up as the 1984-85 928s. Meaning your driver's side carrier and small tooth axle are correct. And your passenger's side carrier and large tooth axle are not.
Please post photos of your rear ABS wheel sensors. Those will be the telling point.
Also, I am hoping more experienced Rennlisters will chime in here soon...
Looks like Seth has unraveled the mystery for you- unfortunately you have some more work to do. I chased an ABS problem for some time before resolving it on my 84 model. I'll offer some info, just in case it is of any help to you.
All four reluctor rings need to have the same number of teeth otherwise the system will not work properly due to the resultant signal generation mismatch. Also the sensor positioning is particularly sensitive from a dimensional standpoint in the bore.
Due to the transition across model year ABS systems, the most straightforward way for you to tell which one you have is to visually inspect all four reluctors in their hubs looking at their 'tooth count'. The odd single one is incorrect- Mr Obvious at your service. You will need to replace the odd hub carrier and ensure you have the appropriately matching reluctor (tone ring) and ABS sensor. (Once that is done, make sure that grounds, harness/connector integrity and relay are all good and functioning, also that the teeth are clean in the gaps with no bridging).
Just to give you a few, 'visual' data points, here are the 84 MY ABS components (this is rear, left hub):
If your rear ABS wheel sensors do NOT look like the below photos, then your 1986 928 has the earlier ABS system:
Hmm. No. My sensors do not look like this... I will add another post with photos soon,,, but they are same (or similar) to the sensors posted in the next post in the thread by Kiln...
Hey! First and foremost I want to thank you guys for the amazing and hard worked (and paid) for information, wisdom and experience! Really...
This is a hard lesson learned but I was foolish to go at this without checking in here with you guys, first! Who would have thunk it. I hear and understand what y'all are putting down. Thank you.
I have some considerations to make...
I will post photos of the sensors, but they match and are like the single bolt on's and deep bore shaft. The donor sensor is from a 85 or 86 928 (same large intake system as mine)...
Clearly, what I have assembled is a hodge podge... So let me ask this first... Should/can I just leave things as are UNTIL (for some reason) I have to deal with a RH rear carrier issue down the line? I mean, the reason I ask, is that let's say I go, find a new and right RH carrier, axle and replace the bearing and put all back together with right parts... Say I do all of that to find the 1, 2 or even 3 of the other sensors are not working properly...? Then what? Sensors (from what I understand) are unobtainable... Then, a few other potential problems may arise. I have never seen the ABS system function properly on this car.
I'm a Sunday style driver, except occasionally, and wonder how often I would need the ABS system..? Sounds lazy,,, but really. Does the ABS system have a negative effect on regular brake function?
Cuz,,, basically,,, what I'm gathering (and I have ZERO concerns with re-selling these incorrect parts) is I need to find an 87 tooth carrier and axle combination... And then MAAAYBE (all stars lining up) I will have a working (but precarious) ABS system.... Still, even if the stars line up and I get it working, problems might be right around the corner.
Ohhhhhhh what to do!
I'm sorry to sound so lax... I LOVE the feel, air, engineering and lots about this amazing machine --- and absolutely respect people's dedication and reverence for the 928, BUT I also am in the middle with a v12 XJS I am trying to sort out. Then an XK8,,, then a Honda Goldwing teardown and cafe racer mode build up. Loooong list.
Q: if I were to find a 87 toothed axle,,, have you heard or have you any experience with a machined SPACER that will work with the tooooo long sensor, in the carrier I have? And since I am asking,,, what the hell carrier do I have anyways, lol? 86.5?
First, inspect and post the pictures of the remaining hubs so when all 4 are compared it will be clear which ABS system you are dealing with.
Second, the spacer idea won't work with mismatched hardware (sensor/reluctor ring combination).
Third, If you are worried about other faulty sensors then conduct this test before buying more items: Jack up the car so wheels are off the ground. With engine on, spin one wheel at a time with a drill attachment or similar and look at the ABS warning light. If you get an error from one wheel when the others are stationary that means the sensor to that spinning wheel is properly working. IIRC, The wheel needs to spin at an approx speed of 5mph or greater to register.
Also, You can check the resistance across each sensor looking for a short between terminals, short to ground or infinite resistance which are failure modes. However, The wheel spinning test will quickly point you to the bad corner.
As an aside, I replaced my faulty carrier hub with one from a parts car, the bearing inside it was good so I didn't have to replace the wheel bearing thankfully.
Just to add, if you pursue the ABS refurb, it might help to get a photo of the hub stampings. On my car (84MY) the part number for left hub carrier was 928.331.219.04 with the upright hub carrier stamping being 928 331 219 OR).
The right rear hub carrier stamping was 928 331 219 OR – photo attached below of stamping number for your reference.
First, inspect and post the pictures of the remaining hubs so when all 4 are compared it will be clear which ABS system you are dealing with.
Second, the spacer idea won't work with mismatched hardware (sensor/reluctor ring combination).
Will not work with wrong hub but RIGHT axle/reluctor if one can be found???
Third, If you are worried about other faulty sensors then conduct this test before buying more items: Jack up the car so wheels are off the ground. With engine on, spin one wheel at a time with a drill attachment or similar and look at the ABS warning light. If you get an error from one wheel when the others are stationary that means the sensor to that spinning wheel is properly working. IIRC, The wheel needs to spin at an approx speed of 5mph or greater to register.
So your saying that proof of it working in this test is that it signals the computer and triggers a FAULT... Clever. On the other hand if it sends no signal (no FAULT detected) it's dead?
Also, You can check the resistance across each sensor looking for a short between terminals, short to ground or infinite resistance which are failure modes. However, The wheel spinning test will quickly point you to the bad corner.
Im terrible with electrical stuff...
As an aside, I replaced my faulty carrier hub with one from a parts car, the bearing inside it was good so I didn't have to replace the wheel bearing thankfully.
Please see above...
Maaaan!!! I want to say how thankful I am for your time and attention. For sharing this!
...Replies in bold below, I'm no expert but hopefully this is of some use.
First, inspect and post the pictures of the remaining hubs so when all 4 are compared it will be clear which ABS system you are dealing with. -
This would be helpful and there are 2 reasons for needing these photos, firstly, to identify which ABS system you have, as the three identical hubs (and hardware) will tell you which toothed version you have. The odd hub will be the incorrect one to be replaced. Secondly, to make sure that the overall hardware combination is correct for the corner that you are refurbing, namely that the correct hub is used with the correct (half shaft) reluctor ring and correct ABS sensor ...and that it matches the other corners. This is 'just to be sure'!
Second, the spacer idea won't work with mismatched hardware (sensor/reluctor ring combination).
Will not work with wrong hub but RIGHT axle/reluctor if one can be found???
I'm not sure what you are thinking of doing but ... The reluctor rings and sensors need to be the same. This is because each ABS sensor sends a signal voltage in millivolts to the ABS controller, the ABS controller compares/ looks for the signals to be matched (within tolerance) between the wheels, because if they are not, then it assumes that one wheel is travelling at a different speed to the other (ie, skidding in rain, etc) which causes the ABS pump to apply brake pulsing. This signal voltage output is (magnetically induced) generated by the sensor as a function of the relative spacing of the reluctor ring teeth.
Third, If you are worried about other faulty sensors then conduct this test before buying more items: Jack up the car so wheels are off the ground. With engine on, spin one wheel at a time with a drill attachment or similar and look at the ABS warning light. If you get an error from one wheel when the others are stationary that means the sensor to that spinning wheel is properly working. IIRC, The wheel needs to spin at an approx speed of 5mph or greater to register.
So your saying that proof of it working in this test is that it signals the computer and triggers a FAULT... Clever. On the other hand if it sends no signal (no FAULT detected) it's dead?
Yes, the one spinning wheel will 'appear' different to the 3 stationary wheels and should trigger a warning. If it doesn't trigger a warning that corner is bad because it is not generating a signal. (If this is the case, the corner investigation should include sensor, harness, ground, positioning, reluctor, debris, connections, etc). Hopefully you are only dealing with an issue on the bad hub - is this the Rear Right - Passenger side LHD?
Also, You can check the resistance across each sensor looking for a short between terminals, short to ground or infinite resistance which are failure modes. However, The wheel spinning test will quickly point you to the bad corner.
10-07-2019, 09:01 PM
1986 Porsche 928 - ABS type hub carrier & sensor issues
