Vibration when driving through water

[longtallsally]

This one is a bit strange.  At speed, and when it is raining pretty hard and there is a bit of standing water in the road, I get a pretty gnarly vibration in the driveline.  Basically everything from the guibo back (csb, lsd, half shafts, wheel bearings, sub frame and trailing arm bushings) has been replaced.

Under throttle, I get a pretty good growling noise and a bit of a vibration at just below freeway speeds.  ONLY time it does it.  As soon as I slow down, it goes away and never comes back.  I have all the heat shields and the like in place.

I'm a bit stumped.  Ideas?

[YetiX]

This one is a bit strange.  At speed, and when it is raining pretty hard and there is a bit of standing water in the road, I get a pretty gnarly vibration in the driveline.  Basically everything from the guibo back (csb, lsd, half shafts, wheel bearings, sub frame and trailing arm bushings) has been replaced.

Under throttle, I get a pretty good growling noise and a bit of a vibration at just below freeway speeds.  ONLY time it does it.  As soon as I slow down, it goes away and never comes back.  I have all the heat shields and the like in place.

I'm a bit stumped.  Ideas?

It's a California car and that shuddering you're feeling is confusion?

[longtallsally]

It's a California car and that shuddering you're feeling is confusion?

Confusion as to what the heck we were thinking moving here!  But seriously, in my other E30s, I never got this, so I'm thinking something is wonky...

[YetiX]

Confusion as to what the heck we were thinking moving here!  But seriously, in my other E30s, I never got this, so I'm thinking something is wonky...

When I was driving mine through the insane rain we had here last month I didn't get any vibration.

I've been trying to think about how water could cause a vibration that didn't happen in the dry. Can't think how blocked drains or anything like that would make a difference.  Maybe it's something to do with the tires?  Like maybe they're breaking lose under the immense torque of your M42 monster?  

Yeah, I've got nothing . . .

[rjcaptsean]

Vibration under throttle usually points to the driveshaft.  Is there any loose bolts either on the guibo or the csb?  Perhaps the csb is not exactly lined up correctly?   Did you lose a balancing weight on the driveshaft?

Yeah, all fun stuff to check since you have to remove the heat shields.   Let us know.

[longtallsally]

I've had a heck of a time with the drive shaft as i recently replaced it. This does point to the CSB, but why only when REALLY wet?

[DesktopDave]

I don't have any idea either.  If I had to guess...hypothetically...I'd think that driving through water is providing maximum resistance.  The standing water decelerates the tires pretty forcefully.  That wide range of force and your description of the noise would make me suspect a bearing.  The rear outer bearings would vary the vibration in turns, so I'd eliminate them as a cause.  It might be the input or output bearings on the diff.  If a seal has failed it might only make noise when fresh water is splashed into the seal.  Diagnosis is pretty easy for that...change the diff oil & check for any water contamination...

The thing that bugs me is that it only happens at a single speed, that's usually a balance issue with a wheel or rotating assembly in general.

[longtallsally]

I don't have any idea either.  If I had to guess...hypothetically...I'd think that driving through water is providing maximum resistance.  The standing water decelerates the tires pretty forcefully.  That wide range of force and your description of the noise would make me suspect a bearing.  The rear outer bearings would vary the vibration in turns, so I'd eliminate them as a cause.  It might be the input or output bearings on the diff.  If a seal has failed it might only make noise when fresh water is splashed into the seal.  Diagnosis is pretty easy for that...change the diff oil & check for any water contamination...

The thing that bugs me is that it only happens at a single speed, that's usually a balance issue with a wheel or rotating assembly in general.

Yeah, good input, Dave.  I'm starting to lean toward the diff as I've got a howl at 50mph.  Wheel bearings are brand new.

[DesktopDave]

Process of elimination.  You've replaced everything else...unless it's something silly like a loose brake pad or something else unlikely.  I was listening to my diff after I posted this and mine is not quiet either...the rest of the car is just drowning it out.  Either that or the car is making me paranoid.

[YetiX]

Process of elimination.  You've replaced everything else...unless it's something silly like a loose brake pad or something else unlikely.  I was listening to my diff after I posted this and mine is not quiet either...the rest of the car is just drowning it out.  Either that or the car is making me paranoid.

Neither of mine has ever been what I would call quiet.  They're not overwhelmingly loud, I just notice it if my radio is off.  The owner of the shop I go to for the bigger stuff drove it and said it's just normal diff noise.  I figure I'll just throw down some Dynomat when I replace the carpet.

[318lotis]

my previous e30 318is did the exact same thing in water. and this car was transported from Honolulu, Hi. , it was mint, no rust, no corrosion. Dave has a good point bout resistance along with not having a great set of tires. I had a very inexpensive st of tires on this car...but the car was awsome till  a drunk women in a tahoe slamed into my rear-end in front of Applebees.

[longtallsally]

Thanks again guys.  I think I must be being paranoid and it is the resistance of the water.  It didn't happen yesterday despite Noah's Ark floating by me on the morning commute and I tried to get it to do it again.

The only thing I can think is that the water is somehow spraying up on the diff or something and causing a cavitation somehow as I have NO symptoms at any other time- and it is not even very often at all when it is wet.