[VP-jiminy]

Hi all! Happy New Year to you!

I wonder if anyone can guide me as to what might be wrong with my E90 328i with 6-speed MT . For the last couple of years the shifter jumps back from the 1st gear into neutral with a forceful thunk only within the first couple of seconds after the car moves. It happens only very occasionally. It doesn't happen if I shift into 1st slowly and hold it in place for a couple of seconds.

Furthermore, what I've noticed lately is when I row through the gears first, i.e shift into 3rd, 4th, 2nd , etc and THEN shift into 1st, it shifts smoothly and the problem has never recurred.

Any thoughts?

I've changed the tranny fluid only once at 94k miles (now car has 149k miles) and used Redline MTL. I read afterwards that Redline MTL is a LT2 fluid, and not the LT3 kind this car needs. Wonder if that's relevant or not.

[marvinstockman]

From Doc Google:

Popping out of gear is a common problem when it comes to manual transmissions. The most common reason a manual transmission would jump out of gear is due to low or contaminated fluid, worn synchronizers inside the transmission, or improperly adjusted shift linkage.

Or you can just start in second gear.

[Slade_]

This happened to me a few weeks ago and scared the hell out of me.

Guess it’s time to change fluids and start poking at the shifters mechanisms.

Currently full bolt on at 106k miles.

[VP-jiminy]

Wonder if a bad clutch slave cylinder could do it.

[e90yyc]

Originally Posted by VP-jiminy

Wonder if a bad clutch slave cylinder could do it.

In the absence of hydraulic pressure the clutch will still be fully engaged—it just won't be possible to release it. So there's no way a bad slave cylinder would cause this.

Check your fluid, shift linkage, and transmission mounts. Unfortunately if it's not something "easy" like that, it's likely internal (synchros, for instance) and would require pulling the tranny to fix.

Regarding fluid choice: I used LT-2 when I filled my gearbox because that's what the sticker on it called for. I've attached a table that shows the recommended fluid based on build date and transmission. Guessing you have a RWD so you'd have the Getrag GS6-17.

[Brian86]

Originally Posted by VP-jiminy

Wonder if a bad clutch slave cylinder could do it.

No

Sounds like every once in a while it's just reluctant to fully engage.

[VP-jiminy]

Thanks, e90yyc. Yes, mine is a Getrag GS6-17BG type. It calls for LT-3 but I'd replaced the factory original fluid with Redline MTL, which I think is LT-2 rated though not sure. Wonder if that has anything to do with the symptoms.
I have 2 liters of fresh Febi Bilstein LT-3 oil. Maybe I ought to start by replacing the current Redline one to that.

[e90yyc]

No problem.

Might as well start with fluid replacement. Let us know how that goes.

[schwing]

My friend's 2006 325i with 6 speed ZF transmission had same issue. Replacing worn synchro solved problem

[e90yyc]

Originally Posted by schwing

My friend's 2006 325i with 6 speed ZF transmission had same issue. Replacing worn synchro solved problem

This is what money’s on.

Did he do it himself? If not, any idea what that ran him $?

[MadJoe]

Originally Posted by schwing

My friend's 2006 325i with 6 speed ZF transmission had same issue. Replacing worn synchro solved problem

My 06 with MT had this problem in 4th due to a damaged synchro. If changing the fluid doesn't help, it's almost certainly a worn out or damaged synchro.