CarlJ

I’ve got a 2013 C4S and just wanted to see if anyone else with a COBB PDK tune was having terrible rattling from the transmission, especially in 7th gear under 2k RPM. I first suspected some LSPI (detonation due to mild lugging), so I switched back to the stock map and filled back up with premium gas with no difference.

I then flashed back to the stock PDK map and it completely went away. So I’ve spent the afternoon flashing and trying various scenarios and ALL the PDK maps cause this terrible rattle in 6th and 7th at low rpm under any load EXCEPT the stock map. Basically cruising on the interstate/highway. This a large majority of my daily commute...

I’m assuming this is due to the decrease in clutch slip they program for at low RPM. Anyways, it’s bad enough that I can’t stand to leave it on there. I’ve done a couple PDK relearns and it hasn’t made any difference.

Anyone else experienced this? I really enjoy the remapped shift points, but it sounds like an old dump truck cruising the interstate.

Bob Z.

What response have you had from Cobb?

Penn4S

First call should be Cobb.

No issues with mine.

CarlJ

I’ve passed emails back and forth with their tech support all day. They said it could be transmission chatter, or normal wear and tear. They said they haven’t experienced it with their shop car. They said I could confirm I don’t have a mechanical issue with the dealership, but when I flash it back it doesn’t exhibit any symptoms, so there’s nothing for them to diagnose... car drives perfect and makes no chatter with the stock PDK shift map and they’re not going to chase issues I’m having with an aftermarket tuner. That’s why I was curious to see if anyone else with an accessport and PDK map has experienced this.

it’s really jerky at low rpm In lower gears too when shifting manually, like the clutch is trying to slip, but there’s not quite enough pressure to hold it so it kind of jerks where it slips and grabs and slips and grabs instead of smoothly slipping. I’m guessing it’s the same thing at speed in 7th and the clutches are chattering. It wouldn’t even be huge deal if it was just in manual mode driving lower in the RPM band than it likes, but it’s still within operating conditions while in automatic mode, so driving on the interstate at 70 is just a constant chatter.

Bob Z.

Fair enough and yes, your thread is justified. I have a manual so I cannot really help but my car stumbled a little for in low gears for a couple hundred miles or so on occasion after I first loaded the tune; however, no noises, etc. How long have it had the tune?

CarlJ

About a week and a half. Driven it quite a bit every day. I’ve got a 60 mile round trip commute to work. I did another PDK clutch relearn and ECU reset this afternoon. Maybe the clutches need to “wear in” a little so they allow for a little extra slip. Just weird that I can go back to stock PDK map and it all goes away. However, they do eliminate a lot of slip in their tune, so maybe it will settle down some.

I’ve got a week or 2 before I run out of their “30 day Guarantee” where I can get my money back if I’m not happy. If I drive on it for another 1000 miles to see if it breaks in, and it never does then I’m stuck with a $2000 paperweight. I’m happy with the tuning and modified shift pattern if it wasn’t for this. Minimal gain on power from the ECU map. Don’t think it’s worth it without the PDK portion.