When I learned to drive, some 60+ years ago, I was taught to use gears to help with braking. Brakes back then were not that great, so changing down to slow down was considered good practice.
Some twenty years later, when I took a Class 1 HGV test, I had to relearn, and the mantra was “gearboxes are more expensive than brakes.”
These rules don’t seem to take automatic gearboxes into consideration. I have been driving automatics, HGVs, and cars since the 1990s and often use the gearbox to slow down. I wonder what the teeming millions think.
When I was first taught to drive a stick shift some 40+ years ago, I was also told to downshift. After I replaced my first clutch, it immediately dawned on me that clutches (and transmissions!) are much more expensive to replace than brake pads.
So I stopped downshifting if I was coming to a complete stop. Instead I just put the clutch in and braked. (Of course I still downshifted if I was just slowing down.)
Now that I drive an automatic, I just take my foot off the gas, let the vehicle downshift itself, and brake when necessary.
In general, engine braking is a good strategy (i.e. just taking your foot off the gas). Engine braking by downshifting is a horrible idea, because you’re unnecessarily introducing wear into the clutch and the flywheel because the transmission has to rev match the engine. This is less of a concern in an automatic because the torque converter generally does that for you, but not if you manually shift to a lower gear (i.e. D to D2).
Also keep in mind that 60+ years ago, most brake system were drum brakes and didn’t slow you down as fast as downshifting. With disc brakes, that’s not really a concern.
Use the transmission to slow down only if your brakes are overheating or failing. Ona very long downhill, it can be be okay. Do not use the gears to slow down routinely (note- big trucks have different rules)
With stick shift/manual gearboxes, being in the correct gear for the speed makes for better control and smoother acceleration as traffic moves on but brakes are designed and built to do the slowing and stopping. Descending hills in a truck safely, requires engine braking, with the aid of a ‘Jake brake’ or similar retarder. You won’t get any anti lock or stability assistance just using the transmission either.
I used to drive big trucks (44-tonne) and routinely changed down to lose speed. Of course, they were mostly automatic. When driving on cruise control, the computer would change down automatically on a downgrade.
Retarders on trucks work by closing off the exhaust valves. The effect is directly related to engine speed, so on a downgrade, changing down will increase the effect.
I have been driving a manuals since the 80s and have always downshifted and have never had to replace a gearbox. I had to replace the clutch pad on a car that I got that already had around 80,000 miles on it, so I’m blaming the previous driver.
My current car is ten years old, only 60k miles though, and no problem with the clutch, gears, anything. On the other hand, I taught two of my kids how to drive a stick on that one. I had a stick that went 100k miles with no issues before I sold it.
I think modern (since the early 90s at least) gear boxes can handle downshifting just fine.
If you’re downshifting (or upshifting) correctly, there should be negligible clutch wear as you rev-match the engine to the new gear before releasing the clutch. The throwout bearing does take some wear regardless of shift technique, but modern versions of those are nearly life-of-the-vehicle. Not so in e.g. 1950 when much of the lore of driving was invented.
And once rev matching is being done correctly, the wear equation changes. Brakes (both pads & drums/rotors) are a consumable that costs money; spinning gears in oil will do that forever without meaningful wear. And are going to do it no matter which gear you’re in, including neutral.
If one is driving a manual, and chooses to use wheel brakes only to slow, the low-wear approach is to shift to neutral, not hold the clutch in the whole time. Ditto while sitting at a traffic light. That saves massively on throwout bearing run time. But … A vehicle in neutral is harder to handle if you do need a burst of power for accident avoidance or whatever. Whether you’re still in the slowing down mode or are waiting at e.g. a traffic light.
[related aside]
There’s an active controversy in motorcycling about whether it’s safer to sit at a traffic light in neutral with clutch engaged or first with clutch disengaged. In the former case, if you’re about to be hit from behind, you probably can’t shift into gear and power out of the situation fast enough. So you’re at risk of being hit by a car. But in the latter situation you’re at risk of the clutch cable failing, the clutch suddenly engaging, and your motorcycle being unexpectedly propelled forward into cross traffic.
My own opinion is better to slow with engine braking, use wheel brakes and clutch disengaged to complete the stop, then stay that way: in first, clutch disengaged. Small increase in throwout bearing wear, some increase in safety. But it’s surely a controversial trade-off.
I owned two manual shift cars, a 1975 Fiat 131 Mirafiori 5-speed and a 2001 Mustang GT 5-speed. For me it was a game to see if I could shift (up or down) by rev-matching the engine to the car speed. I love to hear the synchronizers whir when I shift. That is just me being in love with mechanical stuff. My wife does not understand this nor approve BTW. The Mustang rusted away at 190K miles and still had her original clutch in her.
With regenative braking on EVs and hybrids, this will become less of an issue. They represent only 5-6% of cars on the road today but those numbers will continue to increase. There’s also the CVT transmissions on ICE cars which don’t have traditional downshifting but manage to use engine braking slightly differently.
When I drove a pure ICE car I’d only use engine braking in the mountains.
Racers use brakes to slow down because it is very stressful to use down shifting to create the drag that slows a vehicle, especially at high speeds. My first car was actually a 4-speed manual shift, and I used the brakes to slow down and the down shifting to match the drop in RPMs. This way I avoided “lugging” the engine.
Even if the driver wasn’t very good at rev matching (but gets the right gear), how much is clutch use for stopping ever a problem? Every start off the line has punishing clutch wear, they’re the size of a telephone pole.
The forgotten parking brake or hidden wheel chocks are the ones that make a transmission smell funny.