Thread: Transmission Question.....again

I know that you guys may have seen this post in other sections but from each car I have gotten different answers due to the cars in question having differents setups. So here we go again, I'm reaching out to the community here, what is the noise I'm hearing in between upshifts? Anyone?

In vid 1, rev matching maybe? When you let off the throttle some cars have a crackle... it's prob just that.

Originally Posted by SVTxTERM1NATOR

In vid 1, rev matching maybe? When you let off the throttle some cars have a crackle... it's prob just that.

Well, they are all the Sequential Manual transmissions so that could be a possibilty but why would they let off the throttle? I think it might be something else....

Originally Posted by SVTxTERM1NATOR

In vid 1, rev matching maybe? When you let off the throttle some cars have a crackle... it's prob just that.

Rev-matching is used when down-shifting, not up-shifting, so it would'nt be that if the car is accelerating.

The ecu will pull fuel, retard timing and/or chop the throttle momentarily to help sync the shift and the brief torque limiting can sound weird if the exhaust has been altered. The oem exhaust usually is tuned acoustically to mask this event.

As long as it's not making a scraping sound like gears striping between shifts, you should be fine. If the transmission itself is the source of the noise, a synchronizer is likely damaged.

Originally Posted by JC Hunter

Rev-matching is used when down-shifting, not up-shifting, so it would'nt be that if the car is accelerating.

There are people who do it for both up and down shifting, saw it on the E46 boards. Don't know why you would though.

Idn man, sounds like exhaust crackle to me. I guess go ask the drive what he is doing?

Originally Posted by SVTxTERM1NATOR

There are people who do it for both up and down shifting, saw it on the E46 boards. Don't know why you would though.

Idn man, sounds like exhaust crackle to me. I guess go ask the drive what he is doing?

But these aren't stick shifts, their are sequential manuals (paddles shifters) but yes, the next time I see the driver I am going to ask him.

Originally Posted by SVTxTERM1NATOR

There are people who do it for both up and down shifting, saw it on the E46 boards. Don't know why you would though.

Idn man, sounds like exhaust crackle to me. I guess go ask the drive what he is doing?

If you need to rev-match when up-shifting, you're shifting wayyy too slow. And not everything you see is correct

But I think it's exhaust crackle too.

When you go fron wide open throttle to closed (mid-shift for example) the car engine will spike rich as the intake air slows momentarily and the fuel injection takes a split second to catch up with the change in intake volume. This rich exhaust mixture is then burned by the catalysts and you get your exhaust backfire.

Originally Posted by SVTxTERM1NATOR

There are people who do it for both up and down shifting, saw it on the E46 boards. Don't know why you would though.

Idn man, sounds like exhaust crackle to me. I guess go ask the drive what he is doing?

The rationale behind matching revs on an upshift is to reduce wear on synchros in the gearbox and reduce the wear on the clutch by eliminating slip between upshifts. However, this generally yields a rather relaxed shift speed.