This Is Why It's Difficult To Downshift Into First Gear

Although it's a rare gear change, there are some situations where first gear is preferable for maximum acceleration while on the move, although the transition can be challenging

Michael Fernie

03 Mar 2017

This Is Why It's Difficult To Downshift Into First Gear

Changing gear can become an automotive art form when practiced and fully understood, forming a smooth relationship between ratios, engine speeds and differing shaft speed. Although first gear is generally only engineered to get a car off the line, hairpins and sharp corners can necessitate a change down from a higher ratio to the first cog.

If you have tried this before, you may have noticed just how difficult it can be to slot back into first gear, sometimes requiring a mechanically-unsympathetic shove. The most common situation that this occurs is when drivers are slowing down for a traffic light and pre-empt a downchange into first to get going again.

The problem is that the difference in ratios between second and first is large. So considering the job of a synchromesh is to bridge this gap, the synchromesh for first gear has to work a lot harder than in the rest of the transmission.

A synchromesh is almost like a small clutch that sits on the output shaft between gears, slowing or increasing the required gear’s relative speed to perform a perfect meshing of teeth within the transmission. So when trying to downshift to first, the relative speed difference between the output shaft and input shaft will be large compared to the other less-aggressive ratios.

Let’s take a 2016 Honda Civic’s transmission for example. The ratio for first gear is 3.6:1, meaning that for every 3.6 full rotations of the crankshaft, the gear rotates once. Second gear has a ratio of 2.1:1, third is 1.4:1, fourth 1:1, fifth 0.8:1 and sixth 0.7:1. As you can see, the difference in gear ratio gets smaller and smaller as you go up the gears, meaning the transition between each of them gets easier for the synchromeshes to perform.

The stiffness encountered when changing from second to first gear can also be experienced when committing the blasphemy of selecting second gear from fourth, skipping third gear. The difference in the speed of the input and output shafts of the transmission will be large, forcing the required synchromesh to work harder.

Solutions to help downshifting into first are double clutching and rev-matching. These will allow the transmission the chance to match the speed of the crankshaft, lessening the load applied to the synchromesh for first gear and aiding smoother shifts. Despite this, we wouldn’t recommend regular downshifts into first due to the strain it can put on the components within the transmission. So next time you feel that first gear is necessary to launch out of a corner, make sure you think about the required pedal inputs to perform a smooth shift.

Comments

Rev it and it will slide in like butter when wanting to slow down with the gears even more instead of your brake. Only use I’ve ever had to shift into first when moving.

Does it put strain on the mechanism skipping gears when changing up?
I often go from 2nd to 4th, 5th and even 6th in my MINI Cooper S.
You can get into 6th at 35mph, which I often reach in 2nd gear.

I think the only problem with that is possible stalling the engine, which puts wear on the clutch and whatnot.

When you live in the city, and you live in 1st gear

You don’t, you don’t downshift into first gear….

You do if you drive a 76bhp 2006 ford fiesta :P

I see a lot of comments on here saying things like, “I like to rev match it when I…” or “When I do that I will rev match…” or stuff like that… does everyone not revmatch to change gear?! I just always thought that’s how you were supposed to do it, decelerating, claiming hills, under brakeing… whatever. I have never not rev matched as I always just assumed it was terrible for the clutch… the way I taught myself was if you can feel it, you didn’t change gear smooth enough, try harder.

That’s how I do. I went from 6th to 3rd once and I couldn’t do it then I tried but it was beyond my skill.

yes, Rev-Match is essential for almost all operation. It is also counted as standard procedure every single time we go to a lower gear

it’s also weird when I see a lot of people have no idea what is rev-match.

Ok, I was in shock for a sec… I thought there was no way I would ever kill a clutch if that’s the way that most people drive. I rarely ever ride with anyone, so I wasn’t sure if that’s actually how most people do it.

Remember kids put your car in R for race mode!

And L for Launch!

Skipping gears is not blasphemous

So, I’m the only one that regularly downshifts to first to slow down? I rarely use my brakes to slow down, only to finish stopping.

Even less people rev match on the upshift… downshifting is cool, but apparently so is throwing yourself into the headrest changing into fourth.

Brake are way cheaper than transmission and clutch. You should avoid doing that.

Watching the second video, if that guy would have taken the turn correctly he probably wouldn’t have needed first gear. It was screaming in first anyway and he left it in first after the turn, effectively holding him back.