E46 M3 6MT Shifting Problem

[sbay]

Hope all is well and everyone’s safe and sound. Originally had a problem with the trans where it wasn’t catching gears all of a sudden. Literally went bad in one day and wouldn’t catch gears anymore, especially 3rd and 4th. Got to a point where wouldn’t go into reverse or first at all until i caught it at the right rpm range. Figured it was a sloppy shifter bushing so I changed the lower shifter bushing white cup thing. Nothing.

I got a used trans bc thought it was synchros, clutch was pretty bad, flywheel meh so I changed all three out. Still getting that car not catching gear/throwing me out when shifting. Now it happens mainly in 6th gear, sometimes when i downshift to 4th, but best way to describe it is I’ll be going highway speeds in 5th then shift to 6th and it just doesn’t catch and then I’ll end up revving the engine. I have to really bang it into gear for it to catch almost like I’m tracking the car but I’m going normal highway speeds. Feels like I’m going to break something. Happens when trying to go into first at stop light too, sometimes doesn’t go into the gear and I have to continuously work it until it goes in while everyone’s honking behind me. 3rd and 5th haven’t given me any issues.

Hoping it isn’t a synchro problem with the “new” trans but when I’m going highway speeds and I miss that 6th, rpms drop as usual, and then I catch 6th and it raises rpms and smoothly shifts into 6th so synchros seem fine. Somethings just wrong with the catch/physical shifting into the gear itself. Any ideas on what that might be? Maybe something with the shifter/fork? Maybe I’m doing something wrong since it’s a new clutch and I have to get used to it but I’ve honestly never had a problem with shifting the car. Car has a UUC SSK and DSSR. Appreciate any help and taking the time to read this.

[Slideways]

How are the clutch hydraulic components? Maybe there is air in the system and the clutch is not fully disengaging at times.

Did you replace the guide tube and pivot pin for the clutch fork? Usually, the clutch fork can be reused and synco issues tend to be more common for 2nd and 3rd, but you already replaced the transmission.

[terra]

Maybe a bad compression spring? Tend not to go bad on manuals, but would cause similar symptoms. Bent forks is also possible.

Are you able to get into each gate when the engine is off? Can you get into 6th if you double clutch?

[sbay]

Slideways I did a clutch bleed, changed the slave with an OE slave cylinder, and the pivot pin. Guide tube looked fine. There was an issue where I would press the floor down to the clutch and I would get a vibration/grind in the pedal but I put a clutch stop in and that stopped that. Maybe that can help guide but doubt that’s related. Thank you for the reply.

[sbay]

terra yeah when i try to go into 6th, i get booted out/can’t go in and that’s when I rev the engine. I let go and press the clutch in again, shift to 6th, it catches, raises rpms, and all is good. I did try shifting while off, it’s fine, maybe feels too short but I would’ve noticed something being that I’ve been driving it for a while until it all went crazy past few weeks.

[terra]

terra yeah when i try to go into 6th, i get booted out/can’t go in and that’s when I rev the engine. I let go and press the clutch in again, shift to 6th, it catches, raises rpms, and all is good. I did try shifting while off, it’s fine, maybe feels too short but I would’ve noticed something being that I’ve been driving it for a while until it all went crazy past few weeks.

That does sound like it could be bad synchros on the new transmission too unfortunately.

[reevsy]

Hi... I am experiencing the exact same issues... did you ever find the cause of this? Was it synchros?

Thanks

[sapote]

terra yeah when i try to go into 6th, i get booted out/can’t go in and that’s when I rev the engine. I let go and press the clutch in again, shift to 6th, it catches, raises rpms, and all is good. I did try shifting while off, it’s fine, maybe feels too short but I would’ve noticed something being that I’ve been driving it for a while until it all went crazy past few weeks.

"Hi... I am experiencing the exact same issues... did you ever find the cause of this? Was it synchros?

Thanks"

The OP issue seems to be clutch dragging -- not completely disengaged and caused the synchro not able to let the slider gear to engage the target gear. I don't think this issue is due to bad synchro especially the 6th gear synchro should be like new.

To check if clutch dragging: engine off, shift into first gear, jack both rear wheels off ground, have someone press down the clutch to stopper or wherever you normally target height, then you try to turn the wheel by hand and if it's hard to spin the wheel then it's dragging. Do you have clutch pedal stopper set at proper height? Remember if the pedal is pressed beyond the clutch release point too far, this can cause the PP diaphragm to reverse and grasp the clutch again causing dragging instead of completely releasing.

Doing solo: on a slightly slope place: engine off, shift to 1st, no braking, slowly press down the clutch pedal until the car starts to roll, capture this pedal position. Set the stopper about 1/2 to 1" below the captured point. Obviously if the car won't roll (not by seized brake calipers) with pedal all the way down, then it has issue with master/slave/ or exploding clutch or PP.

[reevsy]

Thank you for your reply.

I guess it makes sense that 6th gear synchro should be ok... Of all the gears 6th should be ok.

if the clutch is dragging, is this the sign of a worn clutch? Cab the travel of the clutch pedal be adjusted from inside the car? I would of thought this we have been self adjusting?

Thank you

[sapote]

if the clutch is dragging, is this the sign of a worn clutch? Cab the travel of the clutch pedal be adjusted from inside the car? I would of thought this we have been self adjusting?

Normal worn clutch should not cause dragging.
Things can cause dragging:
dirty sticky input shaft splines which prevent the clutch disk from sliding freely to free itself from PP and flywheel,
worn and exploded clutch with the fragments dragging between PP and flywheel,
exploded PP touching on clutch,
slave doesn't push the rod far enough


The pedal has the floor stopper for a reason: not let the slave push rod pushing the PP fingers too far and cause dragging.

[sbay]

Hi... I am experiencing the exact same issues... did you ever find the cause of this? Was it synchros?

Thanks

Hey, the fix was changing to another trans. Just had bad luck and the used trans that I got also had bad synchros. Luckily, I had warranty on the used trans so got another one warrantied out. After that, no issues. Guess it’s just luck of the draw with used transmissions for these cars since you can’t fix the synchros.

Best of luck!

[simonnim]

I keep a spare I know works in the corner because of this.