Mystery Vibration

[Finnegan]

I'm posting this in the general section since, well, it's a mystery and I don't know which subsection it would eventually land in.

I'm getting what feels like going over a rumble strip when traveling at 60 to 75 miles an hour. I can feel the vibration through the steering wheel, but also through out the car. It feels ever so slightly like a loss of power, but it feels more like drag than a change in the engine's performance.

It's very difficult to trace the exact location, as the vibration lasts about two seconds or less. It's so short in duration, that it's difficult to localize if it's a left right front wheel, or the drivetrain.

It was repeating itself at intervals of 2 to 3 minutes (almost every 120 seconds, but that pattern didn't hold as I measured it over 60 minutes of driving). Yet on my last drive it only happened twice in 60 minutes of driving.

I don't notice any loss of power on full acceleration or high rpm. I don't notice any unusual sounds turning left or right. I do notice what I would describe as some drivetrain slop when downshifting. (However I'm not sure if that's new or if I'm just paying hyper attention now to everything.) AC on or off makes no difference. Cruise control on or off makes no difference.

Car has 44,000 miles, 15 track days, differential replaced 2,500 miles ago, major inspection (all fluids) done about 500 miles ago.

Potential culprits that I'll be tracing are:

Wheel bearings
Guibo
Driveshaft center bearing

Any other things I should consider?

[dc_wright]

You've got everything I'd put on the list, but I'd change the order and check giubo first just because they seem to wear faster, then center support bearing. Wheel bearings tend to be more continuous.

I just fixed a similar issue on my Toyota Tacoma and it was the center support bearing. It only happened at highway speeds and it would come and go. It seemed to sometimes be triggered by bumps in the road, but not always.

[Finnegan]

Originally Posted by dc_wright

You've got everything I'd put on the list, but I'd change the order and check giubo first just because they seem to wear faster, then center support bearing. Wheel bearings tend to be more continuous.

I just fixed a similar issue on my Toyota Tacoma and it was the center support bearing. It only happened at highway speeds and it would come and go. It seemed to sometimes be triggered by bumps in the road, but not always.

Thank you, that's the kind of direction I was looking for! I'll with your order. Didn't get to the code reader tonight, spent too long fighting with the drip system.

So I get to look forward to the center support barring with my Taco huh?!

[chickdr]

It is funny you mentioned the Taco as I have an '11 base regular cab which has a strange vibration upon deceleration at times. It seems to happen when stopping from around 30-40 miles/hr and was very disconcerting initially(I bought the truck with 20k miles on it in '13). In reading the forums it seems this issue is common in the extended cab truck and has a TSB, but the regular cab is not included although it obviously exhibits the issue.

I wouldn't think mine is the center support since it has been present the whole time I have had my car.

[inTgr8r]

The list so far covers what comes to mind for me.
I also agree re wheel bearings, those are normally consistent, not intermittent

[The HACK]

Street or track pads?

[Finnegan]

Originally Posted by The HACK

Street or track pads?

Track (Pagid RS29 "yellow") plus Stoptech BBK.

I was fighting some uneven pad deposits (street layer wasn't fully removed before bedding the track pads) last time at the track too. Those deposits have probably worn off given cold track pads (kind of sandpaper when cold).

"Pad grab"?

[The HACK]

Do you leave your headlights on the "auto" setting?

Does the "rumble" appear to slow the car down slightly, and happen at intervals almost too consistent to be random?

Has it rained recently where you turned your automatic wipers on?

This may be completely unrelated, but a while back I was chasing a very similar problem. At highway cruising speeds, for long duration of time, I would feel this weird "rumble" that would drive me NUTS. At first it was very faint, I could barely tell anything was going on. It almost felt like the tire noise increased a little, car slowed down just a hair for a second, but not enough to make a difference on the speedo. And it comes and goes, sometimes it does it, sometimes it doesn't. But most of the time when I'm on my way to and from the track, it's there.

Then this one time I got lazy and left the track pads on the car, and on the way to work I felt it again. I couldn't figure out what's causing it except that it's there when the track pads are in the car, not there when the track pad isn't.

One time, I braved the weather and drove to a local track on track pads and track tires, despite the forecast calling for rain (but much later in the day, like at night). As I left the track after a long day (and dinner with track buddies) it started to drizzle. As I sat at a light contemplating whether or not I want to brave the light drizzle to drive home on nearly slick rear tires, the automatic wiper came on and swiped across the windshield.

I made it home that evening without any drama, but it took me a while to put 2 and 2 together. Next time I was driving the MZ4 Coupe, I was going back to Buttonwillow. And there it was. The rumble every few minutes. I was trying to time the interval of the rumbles, but couldn't quite tell because the rumbles varied in intensity and sometimes it just feels like I drove over rough pavement.

Then I noticed on the wiper stalk, the "auto" light is lit.

Something registered on the back of my head. Didn't this generation of DSC have some sort of "brake drying" function that gently put the pad in contact with the rotor every few minutes for a second to keep the rotor dry during inclement weather? I didn't have my manual handy while driving, but I turned my headlight from auto to off, and paid extra attention to the tire noise and sensation through the steering wheel, and it sure seems the rumble has gone away.

Upon further research, the brake drying function applies the brakes lightly every few minutes when the headlight is in ON or Auto, and the wiper is in the Auto mode. For whatever reason, if you switch your wiper stalk to the first position and leave it in auto, if the windshield doesn't get wet, it won't wipe, but it still registers to the car to ASSUME that it's in inclement weather since the condition that both the wiper AND the headlight is in the active position are met to activate brake drying.

While on street pads, the pads in brief contact with the rotor doesn't offer nearly enough resistance to register on the @ss dyno. However, when on good track pads, at cruising speeds near or above the speed limit, the effect is felt through the steering wheel as a temporary grab, a rumble (because cross drilled/slotted rotors on track pads), and a perception that the vehicle is slowing down or losing power. At street speeds, again, this temporary drag isn't felt because you're typically accelerating or decelerating rather than cruising.

So, after that long @ss explanation, check and see if your headlight is set to auto, and if your wiper stalk is up and in auto. If neither conditions are met, then you have a different problem.

[Finnegan]

Originally Posted by The HACK

Do you leave your headlights on the "auto" setting?

Does the "rumble" appear to slow the car down slightly, and happen at intervals almost too consistent to be random?

Has it rained recently where you turned your automatic wipers on?

This may be completely unrelated, but a while back I was chasing a very similar problem. At highway cruising speeds, for long duration of time, I would feel this weird "rumble" that would drive me NUTS. At first it was very faint, I could barely tell anything was going on. It almost felt like the tire noise increased a little, car slowed down just a hair for a second, but not enough to make a difference on the speedo. And it comes and goes, sometimes it does it, sometimes it doesn't. But most of the time when I'm on my way to and from the track, it's there.

Then this one time I got lazy and left the track pads on the car, and on the way to work I felt it again. I couldn't figure out what's causing it except that it's there when the track pads are in the car, not there when the track pad isn't.

One time, I braved the weather and drove to a local track on track pads and track tires, despite the forecast calling for rain (but much later in the day, like at night). As I left the track after a long day (and dinner with track buddies) it started to drizzle. As I sat at a light contemplating whether or not I want to brave the light drizzle to drive home on nearly slick rear tires, the automatic wiper came on and swiped across the windshield.

I made it home that evening without any drama, but it took me a while to put 2 and 2 together. Next time I was driving the MZ4 Coupe, I was going back to Buttonwillow. And there it was. The rumble every few minutes. I was trying to time the interval of the rumbles, but couldn't quite tell because the rumbles varied in intensity and sometimes it just feels like I drove over rough pavement.

Then I noticed on the wiper stalk, the "auto" light is lit.

Something registered on the back of my head. Didn't this generation of DSC have some sort of "brake drying" function that gently put the pad in contact with the rotor every few minutes for a second to keep the rotor dry during inclement weather? I didn't have my manual handy while driving, but I turned my headlight from auto to off, and paid extra attention to the tire noise and sensation through the steering wheel, and it sure seems the rumble has gone away.

Upon further research, the brake drying function applies the brakes lightly every few minutes when the headlight is in ON or Auto, and the wiper is in the Auto mode. For whatever reason, if you switch your wiper stalk to the first position and leave it in auto, if the windshield doesn't get wet, it won't wipe, but it still registers to the car to ASSUME that it's in inclement weather since the condition that both the wiper AND the headlight is in the active position are met to activate brake drying.

While on street pads, the pads in brief contact with the rotor doesn't offer nearly enough resistance to register on the @ss dyno. However, when on good track pads, at cruising speeds near or above the speed limit, the effect is felt through the steering wheel as a temporary grab, a rumble (because cross drilled/slotted rotors on track pads), and a perception that the vehicle is slowing down or losing power. At street speeds, again, this temporary drag isn't felt because you're typically accelerating or decelerating rather than cruising.

So, after that long @ss explanation, check and see if your headlight is set to auto, and if your wiper stalk is up and in auto. If neither conditions are met, then you have a different problem.

Wow and double wow! I thought you were kidding at first with the headlights and wipers but now I see where you're going! I do drive with the headlights in auto or fully on. That makes perfect sense to me--it would also explain the cyclic nature of this. It was so cyclic it was driving me nuts, and I was actually using a stopwatch and lap timer to track its regularity. I kept thinking, how can a mechanical issue repeat itself at such a seemingly consistent intervals. I was thinking is it the ECU running some cycle? It just seemed like it was probably electronic in nature. And your description of what it feels like is spot on.

I'm scheduling a test tomorrow with the headlights totally off, then on.

Note I may have had them fully "off" last Saturday on the first leg of my trip. I didn't notice this issue then. But on the way home I had the lights on, the issue was there, and I know that I had the lights on, because when I got out of the car it pitched a beeping fit because as I'd left the lights in the "on" position!

Thanks!

[The HACK]

No. F**king. Way.

If I'm right about this, I'm going to go and buy me a Powerball Lottery ticket. That was about as wild @ss of a guess as a guess could get. Over the intarweb no less.

Let me know if I need to go plunk down $10.

[Finnegan]

Originally Posted by The HACK

No. F**king. Way.

If I'm right about this, I'm going to go and buy me a Powerball Lottery ticket. That was about as wild @ss of a guess as a guess could get. Over the intarweb no less.

Let me know if I need to go plunk down $10.

Absolutely. Will do!

[AriuSen]

Originally Posted by Finnegan

Wow and double wow! I thought you were kidding at first with the headlights and wipers but now I see where you're going! I do drive with the headlights in auto or fully on. That makes perfect sense to me--it would also explain the cyclic nature of this. It was so cyclic it was driving me nuts, and I was actually using a stopwatch and lap timer to track its regularity. I kept thinking, how can a mechanical issue repeat itself at such a seemingly consistent intervals. I was thinking is it the ECU running some cycle? It just seemed like it was probably electronic in nature. And your description of what it feels like is spot on.

I'm scheduling a test tomorrow with the headlights totally off, then on.

Note I may have had them fully "off" last Saturday on the first leg of my trip. I didn't notice this issue then. But on the way home I had the lights on, the issue was there, and I know that I had the lights on, because when I got out of the car it pitched a beeping fit because as I'd left the lights in the "on" position!

Thanks!

LOL that is crazy!!!
I also feel that my car on highway from time to time loses power for less than a sec. or seems like DCS goes on.....it bothered me a lot....Since I only drive my car to the track, I never change my track pads. PFC 07.
However, my auto wiper is always off and also my headlights....

[Steeler]

Originally Posted by Finnegan

Wow and double wow! I thought you were kidding at first with the headlights and wipers but now I see where you're going! I do drive with the headlights in auto or fully on. That makes perfect sense to me--it would also explain the cyclic nature of this. It was so cyclic it was driving me nuts, and I was actually using a stopwatch and lap timer to track its regularity. I kept thinking, how can a mechanical issue repeat itself at such a seemingly consistent intervals. I was thinking is it the ECU running some cycle? It just seemed like it was probably electronic in nature. And your description of what it feels like is spot on.

I'm scheduling a test tomorrow with the headlights totally off, then on.

Note I may have had them fully "off" last Saturday on the first leg of my trip. I didn't notice this issue then. But on the way home I had the lights on, the issue was there, and I know that I had the lights on, because when I got out of the car it pitched a beeping fit because as I'd left the lights in the "on" position!

Thanks!

You just have to love this freezing forum

[HankDKrank]

That's wild - I thought Hack was pulling your leg there for a bit.

[Finnegan]

Originally Posted by AriuSen

LOL that is crazy!!!
I also feel that my car on highway from time to time loses power for less than a sec. or seems like DCS goes on.....it bothered me a lot....Since I only drive my car to the track, I never change my track pads. PFC 07.
However, my auto wiper is always off and also my headlights....

Common denominator is cold track pads though. We might be wrong about when the drying feature is active.

Originally Posted by dbarton62

You just have to love this freezing forum

Indeed!

Originally Posted by HankDKrank

That's wild - I thought Hack was pulling your leg there for a bit.

Me too!

Update. Inconclusive results as I only had time for a partial test on my way to the shop (alignment). I didn't notice the vibration with the lights off and the wiper stalk in the off position. I did try turning the lights to "on", and I did notice it once. It was hard to do as much open road testing this morning as I wanted given traffic.

I've got a 2 hour drive to the track and back this weekend on 5. I'll run through various testing scenarios.

I really think it's the drying feature being applied in some manner. The clues are adding up and away that strengthens the hypothesis. First, there's the cyclic timing of this. Second there's the common denominator that folks experiencing this having it happen with cold track pads. Third, those affected so far have aftermarket multi-piston brakes. I ran track pads on stock brakes with no issues. (Hack, did you notice this only after going to the RB set-up?) If so the multi-piston set-up may be more sensitive to this. Lastly, there's the way the vibration seems to move forward to rear in a one-two step (at least that's how I'm experiencing it). The vibration seems to start in the front of the car, and then seems to pass through to the rear.

Given brake bias, I think you'd want the front brakes to dry first, then dry the rear. That would be to avoid a situation where you had a lot more rear brake torque than front brake torque in the wet, which would be a very bad thing.

[antennahead]

So, based on the above assumptions, if I had my computer re-programmed to turn the "auto" wiper function to "off", so my intermittent switch works manually, would it be safe to assume I will never have to worry about the computer applying the brakes in wet weather...... especially since I also NEVER use the "Auto" headlight function?

[Finnegan]

Originally Posted by antennahead

So, based on the above assumptions, if I had my computer re-programmed to turn the "auto" wiper function to "off", so my intermittent switch works manually, would it be safe to assume I will never have to worry about the computer applying the brakes in wet weather...... especially since I also NEVER use the "Auto" headlight function?

Probably. The triggers that cause the brake drying feature to be active are still being traced. To cause this issue, you'd also need to run track pads and probably an aftermarket multi-piston BBK.

Edit, found the below from an old press release. Not enough technical detail for me but it does help narrow test parameters.

"Brake Drying improves braking performance in the wet. Driving on wet roads leads to a film of water building up on the brake discs. Naturally this lengthens stopping distances when the brakes are applied as the pads cannot bite the disc as effectively as in the dry. With Brake Drying, the activation of the windscreen wipers or a signal from the screen-mounted Rain Sensor enables a periodic gentle application of the brakes to scrub off any residue. When full stopping power is required, maximum braking force is available. In day-to-day driving, this periodic brake application is unnoticeable and, to avoid any confusion or danger, the brake lights do not illuminate when brake drying is active."

[Finnegan]

Testing shows that to trigger this effect the car must be in auto wiper mode. It doesn't matter if the wipers are engaged. I could trigger it almost at will by moving the intermittent wiping frequency to a faster setting when I'm auto mode. Light switch position did not play into the mix.

[SaltyNC]

Just ran across this thread. WOW!

Salty

[Finnegan]

Originally Posted by SaltyNC

Just ran across this thread. WOW!

Salty

Crazy stuff and a great community ain't it?!

[Huz-Z]

Originally Posted by HankDKrank

That's wild - I thought Hack was pulling your leg there for a bit.

Ditto - but it totally makes sense!