Z4M is back on the road after 3 years

[RossBMWZseries]

I’m sure some of you recall the issues I had with the EWS not syncing to the DME and having no start problems. Well, that was resolved with Severn Tuning’s EWS delete. I have my car back on the road but after 3 years of just being parked in the garage, I may have new issues arising.

Let’s start with a list of performance mods I’ve done to the car while it slept;

I’ve installed;
* Turner’s CSL airbox (Severn Tuning Alpha-N tune currently going through data logging with Josh)
* Turner’s power pulley kit
* AFD Proflex Commander FlexFuel kit
* Section 1 DKF resonators
* Custom straight through X-Pipe
* I burned through the old Premium gas in the tank, poured a bottle of Techron and filled it up with E85

Things I have not done that I probably should do;
* oil change (oil seemed “good” when I checked it but still…)
* I checked all fluids, they’re all topped off but haven’t flushed/replaced any in probably 4 years now


Old issue;
I still seem to be having problems with the K-bus where it’s not communicating any functions on the steering wheel/instrument cluster. Now that I’m able to drive the car I’ll probably take it a few hours from here to a reputable Indy shop.

New issue;
I feel/hear a kick, a thump, coming from the rear. It usually happens when I start to accelerate in 1st gear and/or reverse, sometimes in 2nd gear. It feels odd and concerning to be honest. I don’t know if this has anything to do with the new mods I’ve installed, the old gas that sat in the tank for 3 years, or the tune that still might need some tweaking. Worst case scenario would be the transmission is on its way out or clutch is slipping but I don’t think that’s something that would happen by just having the car sit there.

Also, for the ones that have any type of CSL airbox, i understand the sound changes to a more aggressive deep tone up front, but did your exhaust note also change? Mine sounds angry AF, I love it, but my guess is it’s not normal. It’s not the DKF resonators/custom X-Pipe because it didn’t sound like this until I installed the airbox.

Thanks for taking the time to read. Any insight is always helpful. TIA!

[wdb]

Congratulations on getting it back on the road!

The kick/thump is concerning. I would take a nice long look at the exhaust setup and make sure it isn't fouling something. Also double check all of the bits you had to remove to do the exhaust work.

[maupineda]

It is your exhaust… period. After 3 years you can’t trust your memory.

[RossBMWZseries]

Thanks for the response guys. I should clarify; I installed everything I mentioned except the X-Pipe and section 1 resonators. With that said, I’ve driven the car a few times within those 3 years when the EWS issue was “resolved” with the exhaust already modified and there was no thump. I did drive by my mechanic’s shop and went for a test drive with him. He had all lifts taken up but he sakís it’s not the transmission. Taking his best guess, he stated it was the exhaust rocking back and forth due to some brackets being loose and/or bushings on the transmission. I’ll finalize the tune with Josh first and then address this issue.

[maupineda]

As said, check clearances. I had RE x pipe and it had contact in several places. However, the noise you described may be more of the differential clunk. My car does it.

[RossBMWZseries]

Originally Posted by maupineda

As said, check clearances. I had RE x pipe and it had contact in several places. However, the noise you described may be more of the differential clunk. My car does it.

That’s kinda what it sounds like. How long has your car done it?

[RossBMWZseries]

Im at the muffler shop that installed these sections. They put the car on the lift and found section 1 cracked on the small part that connects both pipes from bank 1 and bank 2. I doubt that’s the issue though

[RossBMWZseries]

They checked the exhaust, retightened everything. I left the shop, still have the thump.

[maupineda]

Originally Posted by RossBMWZseries

That’s kinda what it sounds like. How long has your car done it?

Since I bought it 3 years ago. To the point i wanted to rebuild the diff but apparently is more common that not. So I have accepted it. I will change the gear ratio to 4.1 soon, and will change fluids and use the friction modifier. The prior owner did not use the OE fluid, but since is a thud noise rather than a groan, I think I just suffer of the M clunk 🤬

The car has 80k km, and fluids where changed at 60k, he used redline.

[RossBMWZseries]

Wait, so what you’re saying is that this is somewhat normal? I wasn’t even aware of this

[maupineda]

Yes, search for “M clunk”. That said though, make sure all bushings (diff and drive shaft CSB) are in good order. But our diffs do have a play inside the LSD unit that when the diff locks make the noise. Check if is more present when you start moving with some steering wheel lock, if so, then is the diff locking what causes the thud noise.

[Vanne]

I'd check the center bearing mate