SMG - Does yours blip the throttle on upshifts?

[r4dr]

Something’s wrong. Especially since the car is fully warmed up. That’s the laziest SMG shift I’ve ever seen.

[r4dr]

Also... do you have a carbon airbox? That video just convinced me to get one.

[R1pilot]

Also... do you have a carbon airbox? That video just convinced me to get one.

Fully stock except for the exhaust. I have euro headers + euro cats and a Supersprint exhaust.

[Icecream]

It does look to be shifting slowly. How are foot to floor shifts in S6? I would try that and see what it does. Could be a spring that is weak/broken and slowing the shifts. I can make mine shift like that in S2 and letting off the gas. Do this with caution/last resort (since it has a tendency to induce slurred shifts) but a hard reset might fix it too.

Exhaust sounds really nice in that clip. Is that the SS sport?

[Arith2]

Looks like it's not engaging the gear quick enough. Notice how it flashes and is searching. Once it stops, the clutch engages. Check your SMG codes. There may be a stored fault. You could always try a relearn procedure to see what that does. It tests the system. Did you just convert to CSL?

[R1pilot]

It does look to be shifting slowly. How are foot to floor shifts in S6? I would try that and see what it does. Could be a spring that is weak/broken and slowing the shifts. I can make mine shift like that in S2 and letting off the gas. Do this with caution/last resort (since it has a tendency to induce slurred shifts) but a hard reset might fix it too.

Exhaust sounds really nice in that clip. Is that the SS sport?

I will try it out tomorrow, but I drove it on S5 and it will shift pretty quick.

I bought the exhaust probably 5-6 years ago, I think its the performance one. Its not the race, thats for sure.

[R1pilot]

Looks like it's not engaging the gear quick enough.

Did you just convert to CSL?

I agree on your first statement.

Tune was installed in October of 2016!

[R1pilot]

Thanks for all the comments guys!

I am convinced that this is related to the springs. A year ago I was going through a problem that solved itself, the car would pop out of gear under hard deceleration. Might be related as well even though it stopped all of a sudden.

Time to order some parts, I guess.

[sapote]

I am convinced that this is related to the springs. .

Which one? I would check the one on the long detent pin with a roller with the neutral/gear/ sensor. This detent on the main external shift rod and it can break and jammed. The other rods (1st/2nd and 3rd/4th and R) are on the right side of the box under the cover plate that early model have ball and spring detent that tends to cause high resistance as they worn down the aluminum cylinder edge -- replace the balls with new sleeves; the later cars have sleeve and spring instead which keeps the alignment better. Don't touch the 2 fat pins under the same cover.

[sapote]

[USER="1470"] The 1-2 shift below 2500rpm has to be relatively quick and getting that change in time means putting a bit more unnecessary force on the second gear synchro with cold fluid. Double clutching allows you to be far more gentle with the selector while still matching the synchro speed. These are pretty stout boxes, but it doesn't change that things like synchos are just wear items. They will last a long time if treated correctly. Is it necessary for every M3 driver to double clutch while the car is warming up? No. Will it extend the life of the gearbox? Absolutely. Every M3 owner I know has experience a crunch in second or third gear in their car, and it's because people are too quick with them when it's not appropriate. I have seen these gearboxes stripped down and have seen how they wear. I have talked with one of the few people in the southern hemisphere who is able to service these boxes about this exact topic and the advice is take your time, which sometimes means double clutching up the box.

1) No stress on 2nd gear synchro if slider gear and dogteeth gear are at near same speed and shifting fast. A quick shift is not bad at all if the gears are at same rpm. As about double clutch in this case, what rpm to blip up to bring the input shaft speed up? All are guessing as best, and after blip the input shaft up, then de-clutch, then shift, the cold oil will slow down the input shaft before synchro engagement. Are you blip the input shaft higher than the previous gear rpm to compensate that the shaft will drop off? The only reason to double clutch and blip the input shaft is if the shaft speed drops off too fast from the time de-clutch to next next engaged, and this is the reason why I say to shift faster when upshift with cold oil, and slow down with hot oil, to have matched rpm.

2) I know many boxes have worn 2nd and 3rd synchro but I doubt this was caused by quick shift up with cold oil. It's bad to have a quick up shift with hot oil as gears rpm are not matched.

I do double clutch all the time on down shift, but no need for upshift as I can control the shifting time: fast or slow to have a matched speed gears.

[Thoglan]

sapote Simply put when changing first to second in a single motion means you are applying more leverage on the first set of teeth on the second gear synchro even when the rpm is 'matched'. Two rotating masses will almost never be aligned perfectly even if they are rotating at the same speed, hence why the need for gear oil and why a synchro is a 'wear' item. This extra force is no problem when the trans fluid is at temp but below that splitting the change into two movements means overall less pressure on the synchro. Again, splitting hairs here. This is probably not necessary to keep the gearbox running for the life of the car but it can contribute to wear.

As others stated in this thread, OP's issue is likely something wrong causing the shift to be too slow and the computer is compensating by blipping the throttle. I imagine it runs off a simple program of calculating RPM for the current wheel speed and the selected gear and either blips on a downshift or lets the clutch out when the input shaft drops to the right speed. All I said originally was that it made sense that the SMG system would blip the throttle if it was not able to make the change up in time the same way you might in a manual car on a slow shift or if you were double clutching up the gearbox.

[sapote]

Most of the damages on worn synchro is the blunt dogteeth -- no longer pointed but flat and shorten. It's not the friction material in most case. I had been driving an old 1967 Porsche 912 for many year with worn 1st and 2nd synchros and learned to match rpm to avoid grinding noise. I also rebuilt quite a few transmissions and understand the inside parts. When I say doing a quick shift I don't mean just slam into the next gear, but make a quick motion until touching the next gear synchro, then ease it in. People might declutch then delay too long to bring the next gear synchro into contact, leaving the input shaft speed dropped off too low, then it's bad for synchro. IOW, beside doing double clutch, one can use time to control the input shaft speed for a good match.

[m3nt0s]

Those shifts are way too slow for S4. Curious if the system is low on fluid, and to run through SMG adaptation while our for a drive as it takes only a few seconds.

[R1pilot]

Which one?

No clue! Lol.

I need to start researching this whole thing.

[sapote]

No clue! Lol.

I need to start researching this whole thing.

Yours is SMG so the long detent pin with roller is capped by a plug, LH side. If it broke it could put high resistance on the tail shift rod and cause delay. It located at the same level as the said shift rod.

Also remove the cover plate on the RH side and pull out the 3 springs and 3 balls or sleeves. Replace the balls with the sleeves. Don’t touch the 2 fat pins nearby.

This should ensure no resistance on all shift rods.
I have left out the 5/6 shift rod detent ball on the LH side but it has less chance of being worn.