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Question for gearheads

Posted on 3/2/16 at 1:45 pm
Posted by Spirit of Dunson
Member since Mar 2007
23112 posts
Posted on 3/2/16 at 1:45 pm
Having a discussion with a colleague. Neither of us is a mechanical engineer or similar.

Say you are driving a standard and you are slowing down, like driving into a lower speed zone on the interstate. You are going to go from 5th gear to 4th.
Do you:
a) downshift and then slow down in gear, or
b) take it out of gear and coast for a while before putting it into 4th when you reach your new lower speed?

Is there a right answer?
Is one way better than the other for the vehicle?

TIA
Posted by LNCHBOX
70448
Member since Jun 2009
89397 posts
Posted on 3/2/16 at 1:47 pm to
If I was slowing down just for a lower speed zone, I'd stay in overdrive. Now If I'm dropping from 70 down to 35, I'd downshift and let compression braking do its thing.
Posted by meauxjeaux2
watson
Member since Oct 2007
60283 posts
Posted on 3/2/16 at 1:47 pm to
do not downshift and engine brake. It wears the clutch out.

You tell me.
You want to change brake pads more often or the clutch?
Posted by m2pro
Member since Nov 2008
30087 posts
Posted on 3/2/16 at 1:47 pm to
You shift immediately. Going down in gear will slow you down itself and wind out your rpms.

Well... you slow down first in gear... and then shift.
This post was edited on 3/2/16 at 1:49 pm
Posted by facher08
Baton Rouge
Member since Aug 2011
6314 posts
Posted on 3/2/16 at 1:48 pm to
I never downshift unless I need to for passing.
This post was edited on 3/2/16 at 1:50 pm
Posted by Jobin
Member since May 2009
3600 posts
Posted on 3/2/16 at 1:48 pm to
I always downshift and use the gears to do the slowing for me. Not sure if there's a right answer. All preference I would guess.
Posted by Spirit of Dunson
Member since Mar 2007
23112 posts
Posted on 3/2/16 at 1:48 pm to
I'm talking about the latter situation. Going from 70 to 40 or so. Maybe not an interstate speedzone, but rather exiting onto a lower speed highway.
Posted by LNCHBOX
70448
Member since Jun 2009
89397 posts
Posted on 3/2/16 at 1:49 pm to
It would depend on the traffic.
Posted by AwesomeSauce
Das Boot
Member since May 2015
11633 posts
Posted on 3/2/16 at 1:50 pm to
quote:

a) downshift and then slow down in gear, or

Do not drive a standard if you do this. Either B or let your engine dictate when to proceed to a lower gear and downshift then.
Posted by sleepytime
Member since Feb 2014
3934 posts
Posted on 3/2/16 at 1:50 pm to
Use your breaks instead so people don't rear end you.
Or put it in neutral and coast to a slower speed. Downshifting to slow down causes more wear and tear on your gears.
Posted by meauxjeaux2
watson
Member since Oct 2007
60283 posts
Posted on 3/2/16 at 1:51 pm to
It's fun and more convenient to engine brake but at what cost?
Posted by LNCHBOX
70448
Member since Jun 2009
89397 posts
Posted on 3/2/16 at 1:51 pm to
quote:

Do not drive a standard if you do this. Either B or let your engine dictate when to proceed to a lower gear and downshift then.




The frick? Coasting out of gear is asinine quite frankly.
Posted by Jobin
Member since May 2009
3600 posts
Posted on 3/2/16 at 1:52 pm to
quote:

Going from 70 to 40 or so

So in this case, you'd need more than 1 gear shift to slow down I would assume. In my previous post, I was thinking 70 to 55 or so.
Posted by meauxjeaux2
watson
Member since Oct 2007
60283 posts
Posted on 3/2/16 at 1:52 pm to
All of my manuals I would learn the sweet spot so I could shift without disengaging the clutch.
Posted by Nado Jenkins83
Land of the Free
Member since Nov 2012
66528 posts
Posted on 3/2/16 at 1:53 pm to
Slip in neutral. Coast and brake accordingly. Slide back into applicable gear needed
Posted by Gaston
Dirty Coast
Member since Aug 2008
41694 posts
Posted on 3/2/16 at 1:53 pm to
Depends if you want to slow down rapidly or not. Usually it's 6th to 4th or 5th to 3rd to get any sort of deceleration. My truck does a sync operation so I don't bump the gas, but in the 5 series I rev up before letting off the clutch to match what's about to happen.

I pretty much never let out the clutch out out of gear unless I'm stopped. In coasting I'll just leave the depressed until I needs gear.
This post was edited on 3/2/16 at 2:03 pm
Posted by BoostAddict
Member since Jun 2007
3259 posts
Posted on 3/2/16 at 1:54 pm to
Normally...Slowdown in 5th until the rpms drop to the appropriate shift point then down shift. But it also depends what I'm doing... if I'm wringing a car out, I'll start downshifting and let the engine compression assist the brakes a bit more.
Posted by Spirit of Dunson
Member since Mar 2007
23112 posts
Posted on 3/2/16 at 1:54 pm to
I've always coasted or used brakes while not in gear until I hit my target speed, and then put her back in gear. But I was never properly trained how to drive a standard... Just learned out of necessity over the years.

My colleague told me I was doing it wrong. He said that being out of gear at a high speed was no good, but I didn't get a good reason why.
Posted by LNCHBOX
70448
Member since Jun 2009
89397 posts
Posted on 3/2/16 at 1:55 pm to
quote:

I've always coasted or used brakes while not in gear until I hit my target speed,


Why in god's name would you take the car completely out of gear? Who taught you people to drive like this?
Posted by meauxjeaux2
watson
Member since Oct 2007
60283 posts
Posted on 3/2/16 at 1:56 pm to
quote:

He said that being out of gear at a high speed was no good, but I didn't get a good reason why.

He's thinking about towing an automatic car down the highway. It will burn up the transmission pump if you don't take the driveshaft from the axle.
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