[nsjames]

I suppose it's possible that if there's something physically wrong inside the case it could jam and the servo motors position maybe knock something into or out of the gear mesh. It's a completely gear driven case, so short of not having fluid in it or a bearing failure it's pretty bulletproof mechanically.
I still think you have some sort of mechanical issue in your drivetrain.
the speed sensors will absolutely affect the awd system. It uses that speed sensor data to route power between the front and rear when it detects a difference in wheel speed indicating slip.

[nsjames]

Originally Posted by BMWsandDobermansGirl

That's right. Sucks they didn't have them before. Did you have a rattle?
I'm trying to upload a video of the rattling noise but it won't let me upload mp4.

there's no mechanism to upoad video directly to the message board.
you'll have to stick it on youtube and then post a link.

that's the easiest way anyhow.

[BMWsandDobermansGirl]

Originally Posted by nsjames

I suppose it's possible that if there's something physically wrong inside the case it could jam and the servo motors position maybe knock something into or out of the gear mesh. It's a completely gear driven case, so short of not having fluid in it or a bearing failure it's pretty bulletproof mechanically.
I still think you have some sort of mechanical issue in your drivetrain.
the speed sensors will absolutely affect the awd system. It uses that speed sensor data to route power between the front and rear when it detects a difference in wheel speed indicating slip.

So if the AWD(I mean speed sensors) sensors aren't working and causing this failure, what's the rattling noise about? It was very loud and constant when I took the fuse out for the AWD. I'll try to upload the video to YouTube and link it here so you can hear it.

[nsjames]

Originally Posted by BMWsandDobermansGirl

So if the AWD sensors aren't working and causing this failure, what's the rattling noise about? It was very loud and constant when I took the fuse out for the AWD. I'll try to upload the video to YouTube and link it here so you can hear it.

rattling noise happens in park?
related to engine speed or wheel speed?

if it's a rattle that happens right at startup and before you put it in gear it's probably an exhaust heat shield or something that's hitting an exhaust pipe. That's the most common issue for rattles, especially in cars exposed to salt. The salt eats the heatshields up right at the fasteners and they fall down.

if it rattles in park it's likely not related to your drivetrain problem, as the only thing in the drivetrain that would be getting power is the transmission input. The output wouldn't be doing anything.

[BMWsandDobermansGirl]

Here's the rattling noise which came out after I took the fuse out and the car became "unstuck".

[nsjames]

also, a completely failed sensor will be ignored by the car with an error.

the problems with wheel speed sensors are when they are intermittent, or the tone rings are all corroded up and make the sensor read the wrong wheel speed.

that's what will freak out your ABS/AWD systems. If the car gets incorrect wheel speed data it will elieve that you're spinning or slipping and then the DSC will take action, but it's bad for the case to fully engage the clutch discs on a hard surface with no wheel slip. Wears the clutches.
same reason BMW says you can't have differing wheel diameters on XI cars.

[nsjames]

does the noise change ith engine speed?
where exactly were you filming in that clip on the car?
at the transfer case or farther forward. The transfer case is basically beneath your drivers seat for reference.

but like I said, if the car is in park, the transfer case input isn't getting power and it's not spinning.

[BMWsandDobermansGirl]

Originally Posted by nsjames

does the noise change ith engine speed?
where exactly were you filming in that clip on the car?
at the transfer case or farther forward. The transfer case is basically beneath your drivers seat for reference.

but like I said, if the car is in park, the transfer case input isn't getting power and it's not spinning.

Yes I put the phone under the car near where the driver and passenger seats are, it seemed to be coming from there. No it doesn't matter if I press gas or not. I thought it was a lose piece of metal because I heard it for a second when starting the engine then it's gone. Then I started hearing it while driving fast on the highway, maybe during gear shifts? Only for a second again. But when the car got stuck and unstuck, it became very loud. It's not doing it now that I've been driving it rear wheel.

I will mention the things you said to the mechanic on Monday and I guess we will see what we find then.

I see how getting wrong wheel speed data can really screw up the whole mechanism. There was a noise coming from the back wheel when moving, kind of like tsk tsk tsk, very low. The mechanic thinks it's rust on the sensor. He said if it's rust, he can clean it and put the sensor back hopefully it works. I have no idea how any of this stuff works but I'm using my common sense and imagination. My father has worked in electronics since before I was born so that helps a bit.

Cars are more complicated than woman, that's for sure yet so many men seem to understand them so well! It's very intriguing. 😊

[nsjames]

as someone that's been working on his own junk for 20 years, women are definitely more difficult to figure out.

so the wheel speed sensor is essentially a magnet, and when you pass metal through a magnetic field you get voltage. So you have a magnet very close to a tone ring. The tone ring looks very much like a gear (splines really) and there are high and low spots in it. As the high spot comes to the magnet it changes the voltage, the computer sees this and counts one tooth. It knows how many teeth there are in a revolution.

The problem with cars in a northern climate that deal with corrosion is that the rust fills in the little valleys between the high and low spots, so now the sensor doesn't have nice defined voltage peaks and valleys for the computer to read. and it may count 2 as one if the rust bridges over them, and that's when they will read the incorrect speed, as two "teeth" went by by were counted as one.

commonly this manifests in older vehicles here as ABS issues at low speeds. usually the ABS system engaging when coming to a stop. Cleaning the tone rings with a wire brush fixes them, unless the rust has grown the tone ring in size and eaten the sensor tip.
or in the case of ford explorers they like to rust jack the tone ring and then snap them in the rear.

fun times.
and not a bmw specific issue, just a rust belt one.

regarding your noise.
you hear it at startup and during shifs because that's when the motor moves the most in it's mounts. the mounts are probably a little worn by this point as well.
You heard it when the drivetrain was locked up because when the drivetrain was stuck and you applied power to the transmission it tried to roll the motor over the opposite way. Just like if you revved the car up against the converter with the brakes applied.

I can't say with certainty obviously, but I believe it is unrelated to your drivetrain issue because it was present before hand and it presents while in park, when the rest of the drivetrain passed the transmission isn't doing anything.

[BMWsandDobermansGirl]

Originally Posted by nsjames

as someone that's been working on his own junk for 20 years, women are definitely more difficult to figure out.

so the wheel speed sensor is essentially a magnet, and when you pass metal through a magnetic field you get voltage. So you have a magnet very close to a tone ring. The tone ring looks very much like a gear (splines really) and there are high and low spots in it. As the high spot comes to the magnet it changes the voltage, the computer sees this and counts one tooth. It knows how many teeth there are in a revolution.

The problem with cars in a northern climate that deal with corrosion is that the rust fills in the little valleys between the high and low spots, so now the sensor doesn't have nice defined voltage peaks and valleys for the computer to read. and it may count 2 as one if the rust bridges over them, and that's when they will read the incorrect speed, as two "teeth" went by by were counted as one.

commonly this manifests in older vehicles here as ABS issues at low speeds. usually the ABS system engaging when coming to a stop. Cleaning the tone rings with a wire brush fixes them, unless the rust has grown the tone ring in size and eaten the sensor tip.
or in the case of ford explorers they like to rust jack the tone ring and then snap them in the rear.

fun times.
and not a bmw specific issue, just a rust belt one.

regarding your noise.
you hear it at startup and during shifs because that's when the motor moves the most in it's mounts. the mounts are probably a little worn by this point as well.
You heard it when the drivetrain was locked up because when the drivetrain was stuck and you applied power to the transmission it tried to roll the motor over the opposite way. Just like if you revved the car up against the converter with the brakes applied.

I can't say with certainty obviously, but I believe it is unrelated to your drivetrain issue because it was present before hand and it presents while in park, when the rest of the drivetrain passed the transmission isn't doing anything.

That's really amazing how the speed sensor works. Thanks for explaining that to me. I really do love learning new things. The problem here is the salt that gets sprayed in the streets every winter to melt the snow in the streets. There could also be salt in it. I felt bad this winter because I kept my all season tires on and didn't put my winter tires on so maybe from the lack of changing tires through seasons (not sure if mechanics usually clean whatever's there when changing tires) caused a build up of some sort. I think I noticed them even using a new type of liquid spray on the pavement I think for the back ice and because the salt is actually affecting our lakes as well.
Ford's don't last 5 years here, they rust so much if not sprayed for rust protection.

Yeah I do feel that the noise is just something lose. I'll ask the mechanic to keep his eye out for anything loose. I just hope whatever the problem is doesn't end up costing an arm and leg.

My brother has been fixing cars for a long time too. I always like to learn from him when I can but he lives in another country. Or else we would def have a car lift.

And I think you're right about your first comment. Humans are def more complex than cars, we did make them after all.

[BMWsandDobermansGirl]

Damn, I don't know what's going on! Isn't the car supposed to work rear-wheel-drive with no issues without the transfer case?

I drove it yesterday sort of long distance on the highway and on the way back I had to take the regular roads because the car started making noises on and off while driving. I have no idea what this can be but it sounds pretty bad. Others with bad transfer case or servomotor never mention this symptom.
I recorded 20 seconds of it. I think this noise is connected to whatever caused the car to get stuck and not move at all, accompanied with the screatching noise which is this sound, full blast! 😭

This is quite the mystery.

[BMWsandDobermansGirl]

Dropped my baby off at the garage. He's checking tire sensors first then opening the transfer case. I'll update with results.
Hope y'all have a great Monday.

[BMWsandDobermansGirl]

The servo motor turns and even though it doesn't look like it's in the best shape, the mechanic said it turns and it looks good so that noise while I'm driving that started out yesterday and went away is the actual transfer case.

Not sure it's worth fixing.

[BMWsandDobermansGirl]

I have to update: one mechanic says transfer case, others saying electrical issues!

After the mechanic opened up the transfer case and put it back, the car hasn't made rattling noise again. Apparently this mechanic doesn't change transfer cases (you think he would tell me that from the start! Wth!) so I had to look up a transmission place and there's a place where they are apparently experts about this kind of stuff (I should have went there from the start!)
So I asked for a quote to change the TC, they said they must do a free inspection first they won't do any job before inspecting. What was meant to be a 15min inspection, car ended up staying 2 days with them. They tested it over and over but the noise is gone. The car is back to smooth but still in rwd. The mechanics there also have the same cars BMWs 325xi and they are experts apparently with them.

They are convinced that the issue is ELECTRICAL because the noise comes and goes and wanted to bring in their electrical specialist that charges 250 an HR or something. Geeze! I should have just taken it to BMW for $169! Paid the other mechanic $90 already to check the servomotor but didn't even do what we agreed on. He didn't check the wheel speed sensors which is what we agreed he would do before even opening the TC. (From now on I'm putting everything in writing!) So I'm going back to the first mechanic today and telling him what I think. The other guy should finish what he started right? Can't just tell me he got swamped.

Damn it next time I'm taking it to BMW for diagnostic and none of this headache! I'm going to end up putting much more than that trying to figure out what the issue is.🤯

[nsjames]

and this is why I work on my own junk.


mechanics have proven to be quite unreliable for me.
Even the BMW dealer dicked up a simple drivebelt install and then took three days to respond to me.

[BMWsandDobermansGirl]

Yeah it's true. The BMW guys messed up something on my car as well when I first got it. They had to bring in 4 different ppl to try to figure something out. Same ****, different smell.

My dog is really sick right now and vets are pissing me off even more than mechanics!
I don't know what's going on with the human race....🥴

I'm putting my car on hold in the meantime until my dog gets better. I have to give her IV and medicine everyday, and try to figure out what's going on with her because vets are worst than mechanics & more expensive too! It's mentally exhausting. Once she gets better, I'll get working on my car again. I won't stop till I get to the bottom of everything. As for the car, I do have a huge feeling the problem is in the wheels. The noise in the tires began when the AWD stopped working. Can't be a coincidence.

The car is driving fine RWD right now with the fuse in, just a small rattle when the gear shifts which has been there for a while.

You see, if it was mechanical and the car was stuck not moving, it wouldn't start working again just by taking the fuse out. The fact that it got unstuck when I took the fuse out points to it being an electric issue, right?