lexic

Can you cause wear/damage to gearbox syncros by skipping gears on upshift. That is going from say 2nd gear to 5th gear, 4th to 6th etc...?


Does going from high rpm to low rpm in the gearbox have the same affect on syncros as going from low rpm to high when engaging gears?

I have always been told about double clutching / heel-toeing when down changing to protect the gearbox but never gave thought about the opposite till now.

takahashi

I am not mechanically challenged but I can answer your last paragraph. As a trackie, the reason that I do heel toe is to match the rev in lower gear so I don't have a shift lock.

Shift lock creates oversteer, unless you want to drift. 6000rpm and change to 2nd gear and pop the clutch, you will lock the rear wheel and suddenly you lose traction at the rear. DSC will engage to save your day. This is one of the method that people like Tsuchiya uses

But I cannot see the opposite being true... there is no reason that a low rev can harm an engine or does it

sco

I'm no expert but let's apply some late night logic...

When you're going up a gear you're doing the reverse of downshift. If the revs don't match the current speed on the upshift the synchros will rapidly get them to the correct speed to mesh.

Upshift is naturally easier because the engine speed needs to drop as you upshift as the required RPM for the same speed is lower as you change up. Because normally you come off the accelerator, the engine speed is dropping anyway.

You can't really control the slowing down on an upshift like you can control the speeding up by blipping the accelerator when double declutching on the downshift -- you have to wait for the revs to drop on their own if you don't want to rely on synchro.

So simply, yes if you want to minimise wear on upshift you need to think about the revs, but going 1-2, 2-3, 3-4 and so on isn't much of an issue because of that natural drop in revs if your gear change isn't too slow. Skipping large numbers of gears is a different story. The number of revs when redlining to 60km/h in first then dropping into 4th is significant (around 7000RPM by my reckoning). If you punched into 4th quickly the synchros would need to rapily drop engine speed by around 7000RPM. This will cause much more wear than if you let the revs drop naturally down to the correct speed by doing a really slow shift.

Hope that makes sense.

Im_DANomite

iTrader: (1)

everyday you drive your car it causes wear. but there is no need to worry about it. the wear you cause is so minimal, you'll probably lose the car before you lose the transmission. if driven properly.

RXP33D

I've tried redlining out 1st then to 5th. It caused a shudder as the revs were just way too high for 5th. Altho they meshed, don't think thats good at all.
If you wait long enough for the revs to drop, snap off the clutch at the right RPM as it drops,
you'll be fine. The only downpoint...What's there to enjoy from doin that.
At least snap it down to 2nd, CHIRPPPPPPP!!!, then cruise at 6th if you have to. :D