General Question about your Z4M

[SaltyNC]

Ever since I've owned my Z4MR, I've had the drivetrain clunk that is evidently fairly common. I've ruled out the dual mass flywheel explanation. My clunk or thud is further back than the transmission. I've done the BMW bulletin where the differential flange is greased. I thought that fixed it, but it was a placebo. On my list of possibilities are: differential bushings, rtab bushings or other suspension related thuds, center bearing, driveshaft, and guibo or however you spell it.

I have a few interesting things going on, and I wanted to see if any of you have this with your Z4M.

1. Going down a mountain or long steep hill in 6th gear, the car never gets runaway fast. In most cars I've had, this one mountain drop will cause you to go 90 MPH if you don't tap the brakes. In the Z4M, it never gets above 60. Is that normal? A condition of the gearing? Could it point to an issue with the differential?

2. 1st to 2nd is problematic. I'm not talking about the notchy shifting. Mine is smooth as butter after installing new engine and trans mounts and replacing the fluid. But, when I let the clutch out in 2nd, it sometimes wants to jack-rabbit, surge, pulse, or whatever you want to call it. I have driven manuals for years, so I don't think it is operator error. The CDV has been removed. This seems to be significantly worse when cold.

3. Not often, but every once in awhile, I feel jerkiness, almost like my wheels are slipping when starting in 1st. I'm not launching aggressively when this occurs. I've never noticed any DSC lights flashing. First gear is the only gear I've noticed this. I'm hoping it isn't the trans, but a bit worried.

Any of you ever experience any of the above? Is #1 normal? The car only has 37K on it.

Thanks,
Salty

[StickMon]

1. I've never gone as slow as 60 in 6th, but my car holds 80 with no breaking coming down the Cajon Pass, which is 6% grade for 4 solid miles. I always wrote it off to the high compression engine.

2. I've been driving stick for over 40 years, and still 1st to 2nd is harder to get right in the Z than anything else I've driven. I write it off to the car being very unforgiving due to the high torque to weight ratio. A lesser car will speed or slow the engine slightly using the kinetic energy of the mass of the car. In our cars, the engine dominates.

3. Greasy road? Doesn't take much to get a little slip. Mine chirps the tires on a gentle takeoff just crossing the painted crosswalk lines. A little slip like that won't set off the DSC.

[SaltyNC]

Originally Posted by StickMon

1. I've never gone as slow as 60 in 6th, but my car holds 80 with no breaking coming down the Cajon Pass, which is 6% grade for 4 solid miles. I always wrote it off to the high compression engine.

2. I've been driving stick for over 40 years, and still 1st to 2nd is harder to get right in the Z than anything else I've driven. I write it off to the car being very unforgiving due to the high torque to weight ratio. A lesser car will speed or slow the engine slightly using the kinetic energy of the mass of the car. In our cars, the engine dominates.

3. Greasy road? Doesn't take much to get a little slip. Mine chirps the tires on a gentle takeoff just crossing the painted crosswalk lines. A little slip like that won't set off the DSC.

You're already making me feel a lot better, Stickmon! Sounds like it is all probably normal. Do you get the thuds, also, when coming off the clutch quickly say in a parking lot or reversing?

Thanks, man!

Salty

[StickMon]

That I don't get. Plenty of racket from the dual mass flywheel if I push the clutch in with the slightest positive or negative load.
Especially in 1st gear pulling into a driveway or parking space.
I give it the slightest little gas before hitting the clutch to try and get neutral loading.

[kaybat]

I get no clunking from my clutch.
1)have you done any brake work?My 06MR only has 24K and it had a sticking front caliper when i bought it.(from a dealer,no less)

[SaltyNC]

Originally Posted by kaybat

I get no clunking from my clutch.
1)have you done any brake work?My 06MR only has 24K and it had a sticking front caliper when i bought it.(from a dealer,no less)

I had the brakes/clutch fluid replaced, but no other brake work. I'll check it out.

Salty

[Vanne]

Checked the drivrshaft carrier thingy? Mine made bad clunks on loading and unloading the diff. Replaced that bearing thingy and all was good...

[ShakyDog]

My 3.0i on a grade will just go, no matter the gear. It is like it has no drag, it will just take off. My Tundra will maintain and even downshift if on a grade.

Steve

[3002 tii]

Originally Posted by StickMon

2. I've been driving stick for over 40 years, and still 1st to 2nd is harder to get right in the Z than anything else I've driven. I write it off to the car being very unforgiving due to the high torque to weight ratio. A lesser car will speed or slow the engine slightly using the kinetic energy of the mass of the car. In our cars, the engine dominates.

I don't know what combination of mods did it for me but over the years I've been able to eliminate the first to 2nd first issue

Rogue trans bushing
SSK shifter with taller knob
Mason Engineering clutch pedal (which required me to put back original clutch stop)
Trans fluid drop and fill every 40k with oem stuff

And I generally rev higher and let the clutch out milli second slower from first to second

[SaltyNC]

Originally Posted by Vanne

Checked the driveshaft carrier thingy? Mine made bad clunks on loading and unloading the diff. Replaced that bearing thingy and all was good...

Vanne,

Is this what you're talking about? That's high on my list of suspects. That sounds about where the clunking is happening under the car.



Did you replace it, yourself? Tough job?

Salty

[dc_wright]

Originally Posted by SaltyNC

Vanne,

Is this what you're talking about? That's high on my list of suspects. That sounds about where the clunking is happening under the car.



Did you replace it, yourself? Tough job?

Salty

That's the part Vanne is referencing. That would be the first thing I'd check and the giubo (proper spelling and pronounced jew-bo) would be next.

[SaltyNC]

Originally Posted by dc_wright

That's the part Vanne is referencing. That would be the first thing I'd check and the giubo (proper spelling and pronounced jew-bo) would be next.

Thanks, DC.

Salty

[jdoublehcubed]

Originally Posted by SaltyNC

You're already making me feel a lot better, Stickmon! Sounds like it is all probably normal. Do you get the thuds, also, when coming off the clutch quickly say in a parking lot or reversing?

Thanks, man!

Salty

I also have experienced all three. The first I agree is the high compression engine. The second two I think are some kind of quirk due to the combination of our high torque engine, middling transmission and very low weight.

I also occasionally get thuds coming off the clutch quickly. I've always attributed it to the "m clunk" that many people report in the e46. If you change the driveshaft bearing and it goes away I'd be very interested in knowing.

Also I'm curious how hard it is to change that bearing. I'm thinking you probably need to drop the whole exhaust and driveshaft, and maybe the diff.

[Finnegan]

Sounds normal to me. The first - second is like a secret handshake in this car. Its totally unlike any other manual. My approach has been to keep the revs up by not letting off the throttle-keeping them at 3-4k (or whatever speed req'd to match where revs will land in 2nd). Almost like a heel toe upshift. And yes way more pronounced when cold.

As for the clunk i always shift to 1st let out the clutch a tad then go to reverse. Thats where i notice it most and this other secret handshake seems to work for me.

Car doesn't run away either on a grade--high compression engine there.

Note: this is the same on both Z4Ms we have which is why I ascribe it as normal.

[SaltyNC]

Originally Posted by jdoublehcubed

Also I'm curious how hard it is to change that bearing. I'm thinking you probably need to drop the whole exhaust and driveshaft, and maybe the diff.

Yeah, the exhaust has to drop and the driveshaft. I think it can be removed without removing the diff. I hope so, anyway. I'll definitely update if the center bearing turns out to be the cause. I want to get it on a proper lift and try to reproduce it to see if we can isolate where the thud/clunk is coming from.

I've read so many threads on this, and there seems to be a number of things it can be, and a variety of sounds. Some have chatter and forward clunks (clutch normal), some have metallic clicks/clacks (diff flange splines - technical bulletin fix), some have dull thuds (diff bushings, suspension bushings, ball joints, center bearing, giubo). Some people have Z4's that have never had a single clunk/thud.

Salty

[SaltyNC]

Originally Posted by Finnegan

Sounds normal to me. The first - second is like a secret handshake in this car. Its totally unlike any other manual. My approach has been to keep the revs up by not letting off the throttle-keeping them at 3-4k (or whatever speed req'd to match where revs will land in 2nd). Almost like a heel toe upshift. And yes way more pronounced when cold.

As for the clunk i always shift to 1st let out the clutch a tad then go to reverse. Thats where i notice it most and this other secret handshake seems to work for me.

Car doesn't run away either on a grade--high compression engine there.

Note: this is the same on both Z4Ms we have which is why I ascribe it as normal.

Finnegan, I hear ya, man! What is crazy is that I've been driving this car for 7 months, and thought I finally had shifting perfected, and then this week, it was like I was learning to drive a stick for the first time. Maybe I have a bunion that is affecting my perceived pedal position. I guess it is little quirks like these that make the Z4M a special car. It takes some finesse to learn how to shift, how to handle it properly, etc.

Like you, I rev match quite often, and that does seem to make for smooth shifts when I get it perfect.

Thanks all for the feedback. I know it's an old subject that gets tossed around from time to time. It's one of those things like the vanos rattle -- it's hard to know what is normal and what requires attention.

Salty

[Finnegan]

It's an odd duck!

That "clunk"--is it when going from R to 1st, to R, or at speed? At speed wouldn't be normal.

[SaltyNC]

Originally Posted by Finnegan

It's an odd duck!

That "clunk"--is it when going from R to 1st, to R, or at speed? At speed wouldn't be normal.

The clunk I'm talking about happens on my car in Reverse, 1st, and very seldom in 2nd, but 1st and 2nd are most common. It's definitely when the drivetrain is coming under load or coming off load. For instance, I can put the car in reverse and begin feathering out the clutch. When the car begins to roll about 5 MPH, I can quickly press the clutch in, and "clunk" or "thud." I know that sounds like the clutch, and maybe it is, but the sound to my ear is coming from the area below the car about where the handbrake is located, which is not near the clutch.



Salty

[inTgr8r]

^ It sounds like you're coming off the throttle a little too soon.

[XMetal]

Does the clunk sound like this?

[Vanne]

Just one thud? or tramping?

[SaltyNC]

Originally Posted by Vanne

Just one thud? or tramping?

Vanne,

Just one thud/clunk.

Salty