[Flyboy161]

2012 335i with N55 and 46,000 miles, transmission in normal drive mode. So last night leaving work I got to a traffic light leaving the base. It's a left turn for me onto a 4 lane divided highway and I was turning to the far lane. Light turns green and I half-punched it! As I'm about halfway through the turn, I notice the tach is climbing through 4K until it hit about 5k but I'm not really accelerating any quicker. About then I feel a little bump in the seat of my pants and the car starts accelerating again.

Three theories:
1. The torque converter didn't grab right away between shifts from first to second, or...
2. Transmission slipping, or....
3. Just a long shift between first and second gear

I don't make too many right hand turns from a stop like that so I haven't really noticed it. But this happens in wide left turns from a stop.

Thoughts?

[fun2drive]

You missed the real cause low Life Guard 6 transmission fluid. I suspect your transmission is leaking via the mechtronic sleeve or another seal on the top of the transmission. Don't screw around with this. Go to the auto hobby shop and put it on the rack. Take the fiber cover off the transmission and locate the fill plug which is on the side. Break it loose and it will take incredible force to do so. I think it is a torx. Don't remove it just break it loose. Lower the lift start the car and then raise he lift back up. Your transmission temp needs to be between 80-120F to do this. Now with a pan under the fill port take the fill plug out. If anything weeps out your transmission level is fine. My guess is that you need LG6.
You can order it from our vendors and not many places carry it but a compatible substitute is Mercon SP which you can get at most parts stores. They may have to order it for you but it is 6 bucks a L vs 20 bucks a L. I know it is compatible as I sent samples to Blackstone for analysis and they came back the same and Ford required ZF to function with Mercon SP.
Hope that helps....

[Flyboy161]

I appreciate that response. Auto hobby shop...Robins AFB closed their auto hobby shop about 2 years ago.

I'll check it out though.

[tdavis42]

Try making the same turn with all the nanny's off. If it still happens you have a problem if it doesn't then its DSC/DTC kicking in.

[fun2drive]

Your symptoms are classic for low fluid and that would be the best of all things since other things could be expensive.
How about Warner Robbins do they still have an auto hobby shop? Either that or find a good indy BMW tech since doing this on jack stands is a royal PITA.

Always do the simple things first and that is the very first thing to check.
Sucks that they closed the auto hobby shop one of the benefits that really helps maintain your ride...

[Flyboy161]

Originally Posted by tdavis42

Try making the same turn with all the nanny's off. If it still happens you have a problem if it doesn't then its DSC/DTC kicking in.

I'll try that tonight. That was something that crossed my mind

[Flyboy161]

Originally Posted by fun2drive

Your symptoms are classic for low fluid and that would be the best of all things since other things could be expensive.
How about Warner Robbins do they still have an auto hobby shop? Either that or find a good indy BMW tech since doing this on jack stands is a royal PITA.

Always do the simple things first and that is the very first thing to check.
Sucks that they closed the auto hobby shop one of the benefits that really helps maintain your ride...

Yeah, I'm retired from the service now. Work civil service, though. So many benefits have gone over the years, it's really disappointing. I'm afraid that turning wrenches on your ride is a lost art. I have a pretty well stocked garage at home and enough skills to tackle any job.

So tonight I duplicated the rev-thump same place with DTC and DSC "ON". I think tDavis42 may be on to something. I'll confirm it tomorrow night. I did flop over to Sport Mode at another left turn later and had no issue. The car is a CPO with maintenance plan, so if it gets to ugly I'll swing by the dealer and let them check it out. Right now it's a very limited occurrence. But I'll keep a close eye on it. I have no leakage from underneath the car (I check often).

[doru]

Originally Posted by Flyboy161

Stuff deleted

So tonight I duplicated the rev-thump same place with DTC and DSC "ON". I think tDavis42 may be on to something. I'll confirm it tomorrow night. I did flop over to Sport Mode at another left turn later and had no issue. The car is a CPO with maintenance plan, so if it gets to ugly I'll swing by the dealer and let them check it out. Right now it's a very limited occurrence. But I'll keep a close eye on it. I have no leakage from underneath the car (I check often).

With the transmission leak (if any), you would be really "lucky" to see spots under the car (or maybe that won't be that lucky, because it would be a massive leak). You need to physically raise the car, take off the protective shield and inspect, because as you drive, the leak will go on the pavement as you drive. In the garage, with car not running it won't leak, hence no obvious signs. I had a car where the mechatronic O-ring was leaking badly and had similar symptoms as yours. The old O-ring was black and was a known source for leaks. The updated O-ring was orange in color (if I remember correctly) and fixed the issue (At that time I did also fluid & filter change). There is special method how to replace the O-ring, the sealing sleeve has only a small gap after installing it correctly, otherwise it will leak badly. I have that document at home somwhere on my computer, it's for a ZF tranny (I believe you have the French GM), but it's the same procedure I believe. If you need it, pm me and I will send it to you.

GL

[Flyboy161]

It's a ZF6HP19. So the mechatronic sleeve you guys are referring to is the sleeve that the electrical connector attaches to right? And the gap should be 2.5-3.0mm?

[Flyboy161]

Found it. Not a leak and not low on fluid. It is a known condition that affects the ZF6HP19 during engine warm up. Does not occur in Sport mode. The NIC (Neutral Idle Control) feature disengages the torque converter from the transmission when the vehicle is stationary in the Drive position; the service brakes are applied; and the engine is still in the warm- up phase. The NIC function eliminates engine load when vehicle is stopped, reducing fuel consumption.
Their solution is to reprogram and recode the complete vehicle with a current Progman version. If it is still to harsh then deactivate the NIC function by performing the "Converter lockup clutch" retrofit, using the current Progman/ISTA P version.

[tlow98]

Interesting. I think the n51 does something similar.