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Down shifting effect

10K views 24 replies 13 participants last post by  mschipa 
#1 ·
My 16 Hellcat is the first manual transmission I've owned. So I am wondering if downshifting wears out the motor or trans sooner. Also, is it better just to pull it out of gear and or ride the clutch (fully disengaged) I am having a blast with this car but I want to be sure I'm not doing any damage to it. Any advice would be greatly appreciated.
 
#2 · (Edited)
It doesn't - you don't want to ride the clutch or hold in the pedal any longer than necessary. The moment you lift off the gas and have clutch engaged, the engine would be doing compression braking anyway.

The key is clutching smoothly and with minimal slipping (for longer clutch life) and minimizing that transition of on/off the clutch.

I downshift all the time, for curves or grades where you want the lower gear for control, accelerating out of a curve, or grade changes, or if traffic flow changes.

If coming up to a light, shift to neutral and off the clutch vs holding in the whole time.
 
#3 ·
I am assuming the smoothest transition is doing it without feeling the "backlash"(I guess its called) as the clutch is released. I have noticed that takes longer to accomplish at lower RPM shifts 2000 or so. The quicker the clutch is released the harder the jolt.
 
#6 ·
I have been driving high horsepower cars with manual transmission for a long time now.
I down shift all the time. There are times when I'm lazy where I'll throw it in neutral and coast to the stop sign or light when city driving and in third or second gear but it's not often.
Just make sure your not down shifting to early, putting the rpm's so high. It won't hurt the car but no need to let the engine work that much harder on a down shift. Once in awhile you do have to hear the beast roar though, Lol...

Like I said before I've had many manuals and this car is by far the best shifting, smoothest, most fun manual I've ever experienced. Can't believe how buttery smooth it is at low speeds. No bucking, surging..anything, it's amazing!

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#7 ·
Downshifting doesn't affect the engine or trans as long as you don't over-rev the engine by shifting to too low of a gear at too high of a speed, if you don't rev-match and instead slip the clutch to help get the engine RPM to match and get smooth clutch engagement when downshifting then that slippage will have an effect on clutch wear over time. The clutch is similar to brake pads, the more friction created by slippage across the surface the faster they will wear. Driven normally, you shouldn't have to worry about replacing the clutch for at least 60k miles or more. As you drive the car harder and slip the clutch when drag racing, etc, the clutch lifespan will be reduced.

Similarly, coasting with the clutch pedal depressed when coming to a stop and then keeping the pedal depressed will weaken the pressure plate fingers over time and will reduce the clamping force, eventually leading to the clutch slipping under high torque loads.

Not to worry, though. These clutches aren't fragile and if you end up slipping the clutch excessively for some reason then the clutch will tell you by smelling horrible due to being overheated.

You also do not want to be coasting in neutral with your foot off the clutch, that is unsafe because you won't be able to react to a sudden need to accelerate or get out of the way of something unexpected.

If coming up to a light, shift to neutral and off the clutch vs holding in the whole time.
I'm going to disagree with this one for safety purposes. It's unlikely, but as mentioned above if you need to take evasive action then being in neutral with your foot off the clutch is going to delay your ability to react.

It's all about practice. The clutch and drivetrain will be happiest with the quickest and smoothest shifts possible. Too slow/too much clutch slippage wears the clutch, clutch engagement that's too fast and results in jerky shifting or wheel hop causes high shock loads on the driveline and suspension parts.

Glad you're enjoying your HC! :)
 
#9 ·
I used to downshift to slow things down but only really do that in trucks now. For cars it is unnecessary and brakes are cheaper than clutch work.

That said, I think if you're good at rev matching the difference is probably negligible.
 
#11 ·
Its fun to downshift and let the exhaust pop... but when you "engine brake", you are torquing the transmission in the opposite direction it was engineered to perform in. If you need to slow down, use your brakes and rev-match the engine/trans speeds. Pads and rotors are a lot cheaper than a transmission. And you will be beyond pissed when you pay so shop $1,500-$2,000 to replace an $8 pilot bearing you messed up from engine braking for a year or two.
 
#12 ·
This is wrong on so many levels. You're not hurting anything by downshifting and engine braking.


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#18 · (Edited)
Sounds reasonable.

I guess my idea of what engine braking is, is wrong. What you are calling engine braking, I know as engine braking for big trucks. Never considered it engine braking in gassers, especially cars, because most has cars don't have enough compression to effectively slow the vehicle, especially at very high speeds.

I had some wheel hop an occasion with the race car, but most of the time the car was hooked pretty well. You mentioned corners though... I was doing drag racing and engine braking as hard as possible to stop the car before the track ended. I wasn't doing road course stuff back then. I put some beefy brembo brakes with power slots and ceramic pads so I could pedal the brake instead of relying so heavy on the trans.
 
#19 ·
Sounds reasonable.

I guess my idea of what engine braking is, is wrong. What you are calling engine braking, I know as engine braking for big trucks. Never considered it engine braking in gassers, especially cars, because most has cars don't have enough compression to effectively slow the vehicle, especially at very high speeds.
Actually, gas engines have more actual engine braking than diesel engines. Diesel engines are horrible for engine braking unless they're equipped with either a compression brake or exhaust brake, the reason is that diesel engines don't have a throttle blade. Gas engines have engine braking not because of compression but because of vacuum resistance from the throttle blade being closed. Engine compression does nothing for engine braking because when you have one cylinder coming up on the compression stroke you have another cylinder coming down on the power stroke (Just without any power besides the compressed air because there's no fuel injected when engine braking), the compressed air in the cylinder acts like a spring, so the piston pushing up to compress the air is negated by the compressed air pressing down on another piston as it travels down the power stroke.

Diesel compression brakes function by taking the spring effect out of the equation, the engine compresses air on the compression stroke and just as the piston nears TDC the compression brake opens the exhaust valve to release the compressed air. By doing that, the engine is able to slow down quite well because it's always only fighting compression and there is no "spring" pushing the piston down on the power stroke.

Exhaust brakes are what they sound like, either a valve in the exhaust or a VGT (turbo) that is able to restrict the exhaust flow and provide resistance during the exhaust stroke.

I had some wheel hop an occasion with the race car, but most of the time the car was hooked pretty well. You mentioned corners though... I was doing drag racing and engine braking as hard as possible to stop the car before the track ended. I wasn't doing road course stuff back then. I put some beefy brembo brakes with power slots and ceramic pads so I could pedal the brake instead of relying so heavy on the trans.
Gotcha, sounds like you were really being quite hard on those transmissions and I'm honestly not surprised you had problems. Those kind of shock loads are never good.
 
#21 ·
also - on these Tremec setups - the throwout bearing / slave cylinder are one unit $118 - 133 for the part and a whole lot of labor time to R & R the transmission for that.
 
#25 ·
What Hal H. said...

I read a great "10 steps on how to drive a manual transmission" article in Car and Driver probably 20 years ago. It went something like this:
1) Do not use the clutch to hold the car on a hill
2) KEEP YOUR FOOT OFF THE CLUTCH
3) Do not use the clutch to slow down at a light, brakes are cheaper than clutches
4) KEEP YOUR FOOT OFF THE CLUTCH
5) The goal is smooth...
6) KEEP YOUR FOOT OFF THE CLUTCH

You get the idea. It was a great way to demonstrate that your best bet in never having to replace a clutch, pressure plate, or throw out bearing is to be smooth and KEEP YOUR FOOT OFF THE CLUTCH. I still remember that article to this day (obviously) and it did change the way I viewed how to drive a manual. I know that some disagree with #3 but I'm just writing what was in the article and it is not necessarily my view (though it is and that's what I do).

Mike
 
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