[vinxter]

My car e92 323i (2.5L N52 and GM Gearbox) has been plagued with a weird issue for a while now. It randomly happens, mostly at low gears which I would assume gear 1 shifting to 2 at around 3000rpm. My usual experience would be, the car moves till it reaches above mentioned and the gearbox would act up in a way where it struggles to lock/shift into the next gear. When this happens, rev needle keeps fluctuating around 3k rpm till it catches on to the next gear.. However it’s worth noting that this usually happens only when i accelerate after going through a bump or after a hard break. It also occurred randomly when coming out of junctions which is pretty dangerous as the car would just remain ‘powerless/hunting for the right gear’ for a few seconds. Also happened a few times during slow traffic and when i accelerate to take over some cars. I have taken a video to explain and u can actually hear how the engine/drivetrain and rev needle reacts. This was taken when i accelerated after crossing a small bump.

Ive sent it to a local expert workshop but there were no codes. Cleaned my vanos but doesnt seem to work. Gearbox oil, coils checked out okay. They told me that it would be better to change a gearbox as it would be difficult to figure out whats wrong as there were no codes. Unlike the zf gearboxes, i am not experiencing the usual hard shifts/shudders when coming to a stop. There are times where i can feel a harsh shift though when gears are changing, as if there's a light 'klunking sound'. Hopefully someone can guide me in the right direction. Here is the link to the vid:

When this happened, my foot was still on the pedal. Rev needle stutters and the car loses power (slightly jerks) till it catches on the gear again. What i could not understand is it hardly happens on a straight road.

[vinxter]

Bump. Would love if i could get some help. The issue is getting really annoying and i have changed the trans oil & filter. Vanos was cleaned as well. No codes detected..

[e90yyc]

Hmm. At first glance it looks like a pressure issue, but by no means am I an expert in this area. I don't have a turnkey solution for you; I think you'll need to do more analysis including using a diagnostic tool to look for pressure values within transmission valve body that are not within proper ranges. Once you've got a better idea of what the actual issue is, then you can move to actually implementing a fix.

Something that really grinds my gears (sorry...) is how unwilling most professionals are to actually diagnose and repair things. Don't get me wrong -- sometimes it makes no sense to chase an issue if replacement is more economical. Butttt, if this is the only issue you're having with your transmission, my inkling would be that it can be fixed for less than a replacement. Especially given the mileage on your car. Needing a new tranny at 100,000 kilometers seems a bit unusual, unless there was serious neglect/constant low fluid levels, etc...

The good news is that if you do end up needing a new unit, the GM 6L45 gearboxes are fairly common and can be had for a somewhat reasonable price. I'm not 100% sure what components beyond the control module are specific to the E90.

I'm about to do some transmission work on my 2007 328xi, but my car has 280,000 kms on it...

If you haven't yet, bring your car to an actual transmission specialist. They can hopefully look at the values necessary to home in on the issue at hand, and give you a more informed answer as to whether your problem really warrants a replacement tranny.

Good luck man

[Big Mexican Women]

change transmission fluid and filter. replace solenoids and valvebody.

[labrador]

How about shifting manually? Will it still do it?

And turn off stability control to test.

[pmutuku]

Cool