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Downshift before WOT? #5439672 05/26/20 08:01 PM
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Avery4 Offline OP
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Hello everyone, I am wondering if it is better on an automatic transmission to manually downshift it to a lower gear before flooring it so it isn't downshifting under heavy load. For example, of I am going 50 and I decide to floor it, is it best to floor it and let the ECU downshift it to 2nd gear automatically or is it it best to manually downshift it to 2nd gear and then floor it? I would think it would be best to downshift to the appropriate gear before flooring it, it would seem that downshifting under full throttle would cause significantly more wear on the clutches than downshifting it under a light load before flooring it. Thanks in advance!

Re: Downshift before WOT? [Re: Avery4] #5439677 05/26/20 08:05 PM
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fsdork Offline
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I find the manual downshift function of most automatic transmissions to be fairly jarring. I imagine the exception would be something with a sport shift/flappy paddle setup. I will usually find the sweet spot in the accelerator travel that causes the transmission to downshift, then floor it from there, for the reason you are describing. I suppose it all comes down to how your particular vehicle feels when you use one method vs the other.


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Re: Downshift before WOT? [Re: fsdork] #5439688 05/26/20 08:10 PM
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Avery4 Offline OP
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Originally Posted by fsdork
I find the manual downshift function of most automatic transmissions to be fairly jarring. I imagine the exception would be something with a sport shift/flappy paddle setup. I will usually find the sweet spot in the accelerator travel that causes the transmission to downshift, then floor it from there, for the reason you are describing. I suppose it all comes down to how your particular vehicle feels when you use one method vs the other.

Thank you. Manually downshifting my car (a 2005 Civic with higher than stock line pressure) under light load (just cruising) is quite jarring, even with the torque converter unlocked. Hard shifts actually generally cause less wear on the clutches than smooth shifts since they slip for a shorter period of time. However, the jarring doesn't bother me and I would think that shifting under a light load would cause significantly less wear on the clutches than shifting it at full throttle, especially since I modded my engine to make about 30 HP more than stock.

Last edited by Avery4; 05/26/20 08:12 PM.
Re: Downshift before WOT? [Re: Avery4] #5439707 05/26/20 08:33 PM
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14Accent Offline
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That really depends on the situation and the vehicle. An old, hydraulic and vacuum operated auto? Possibly, but still probably wouldn't make too much difference.

A brand new vehicle, with a 10 speed auto and computing power that rivals NASA? No chance it will help. The new cars read accelerator position, load, throttle position, gear, TCC slip, and many more faster than you can decide to put on your turn signal. When you floor that throttle, believe you me the car is making MANY more decisions than just "full power and downshift". It's adjusting transmission line pressure, timing, fuel pulse, actual throttle position (on electronic throttles), and much more. You'd be hard pressed to get a better downshift than what a modern ECM can provide.


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Re: Downshift before WOT? [Re: 14Accent] #5439720 05/26/20 08:47 PM
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joekingcorvette Offline
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Originally Posted by 14Accent
That really depends on the situation and the vehicle. An old, hydraulic and vacuum operated auto? Possibly, but still probably wouldn't make too much difference.

A brand new vehicle, with a 10 speed auto and computing power that rivals NASA? No chance it will help. The new cars read accelerator position, load, throttle position, gear, TCC slip, and many more faster than you can decide to put on your turn signal. When you floor that throttle, believe you me the car is making MANY more decisions than just "full power and downshift". It's adjusting transmission line pressure, timing, fuel pulse, actual throttle position (on electronic throttles), and much more. You'd be hard pressed to get a better downshift than what a modern ECM can provide.


+1


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Re: Downshift before WOT? [Re: 14Accent] #5439721 05/26/20 08:48 PM
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Avery4 Offline OP
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Originally Posted by 14Accent
That really depends on the situation and the vehicle. An old, hydraulic and vacuum operated auto? Possibly, but still probably wouldn't make too much difference.

A brand new vehicle, with a 10 speed auto and computing power that rivals NASA? No chance it will help. The new cars read accelerator position, load, throttle position, gear, TCC slip, and many more faster than you can decide to put on your turn signal. When you floor that throttle, believe you me the car is making MANY more decisions than just "full power and downshift". It's adjusting transmission line pressure, timing, fuel pulse, actual throttle position (on electronic throttles), and much more. You'd be hard pressed to get a better downshift than what a modern ECM can provide.

That is true. I know that some vehicles will cut power briefly during shifts either by closing the throttle (on cars with an electronic throttle unlike mine) and/or by retarding ignition timing or cutting off the fuel injectors during the shift. However, I don't know that my old Civic's ECU is fancy enough to do anything like that. I don't feel it cut power during shifts, but I quite possibly wouldn't feel it.

Last edited by Avery4; 05/26/20 08:49 PM.
Re: Downshift before WOT? [Re: Avery4] #5439732 05/26/20 08:54 PM
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eljefino Offline
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^ Yeah, my wife's HHR with electronic throttle did smooth downshifts.

Re: Downshift before WOT? [Re: Avery4] #5439753 05/26/20 09:35 PM
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CT8 Offline
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Why is it called an automatic transmission?


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Re: Downshift before WOT? [Re: Avery4] #5439820 05/26/20 11:36 PM
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Hermann Offline
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When I choose to use the manual mode on my Ford 6R80 automatic, the manual downshifts are anywhere from smoother to much smoother. Note that I did not say quicker, I think the computer is retarding something to make this possible.

When I switch to Sport mode, the manual shifts both up and down are very quick and not that much harsher than in Normal Mode. To be fair, in Sport Mode the Automatic improves greatly with quicker and less sloppy shifts, also holds the lower gear longer. My only complaint with the tranny is a small percentage of the time, seems to downshift one to many gears. The times it downshifts one too many gears, the second one is from harsh to very harsh. Less harsh after the transmission fully warms.

I find myself using the Manual Mode semi frequently. I have this one country road where you come down a hill at about 50 mph. At the bottom there is about a 75 degree right hander. It is a blast to hit the apex in second at 45 mph and hit the gas hard and run through the gears at high RPM up a long slow rising hill. It's a blast

My 2ยข on the matter.


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Re: Downshift before WOT? [Re: CT8] #5439869 05/27/20 05:24 AM
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supton Offline
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Originally Posted by CT8
Why is it called an automatic transmission?

Because in the bad old days you had to manually pick the wrong gear--today it can automatically pick the wrong one for you!

From what I've read, some programming is excellent, other transmissions... a bit less so. I drove manuals for 20 years and still think I know how to pick a gear just fine.


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Re: Downshift before WOT? [Re: 14Accent] #5439871 05/27/20 05:29 AM
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demarpaint Offline
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Originally Posted by 14Accent
That really depends on the situation and the vehicle. An old, hydraulic and vacuum operated auto? Possibly, but still probably wouldn't make too much difference.

A brand new vehicle, with a 10 speed auto and computing power that rivals NASA? No chance it will help. The new cars read accelerator position, load, throttle position, gear, TCC slip, and many more faster than you can decide to put on your turn signal. When you floor that throttle, believe you me the car is making MANY more decisions than just "full power and downshift". It's adjusting transmission line pressure, timing, fuel pulse, actual throttle position (on electronic throttles), and much more. You'd be hard pressed to get a better downshift than what a modern ECM can provide.

I agree.


God Bless Our Troops

Re: Downshift before WOT? [Re: supton] #5439905 05/27/20 06:56 AM
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Originally Posted by supton
Originally Posted by CT8
Why is it called an automatic transmission?

Because in the bad old days you had to manually pick the wrong gear--today it can automatically pick the wrong one for you!

From what I've read, some programming is excellent, other transmissions... a bit less so. I drove manuals for 20 years and still think I know how to pick a gear just fine.

I have driven 3 on the tree through 13 speed Road Rangers manual transmissions , thank you I know how to shift very very good myself.


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Re: Downshift before WOT? [Re: CT8] #5439906 05/27/20 06:58 AM
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supton Offline
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Originally Posted by CT8
Originally Posted by supton
Originally Posted by CT8
Why is it called an automatic transmission?

Because in the bad old days you had to manually pick the wrong gear--today it can automatically pick the wrong one for you!

From what I've read, some programming is excellent, other transmissions... a bit less so. I drove manuals for 20 years and still think I know how to pick a gear just fine.

I have driven 3 on the tree through 13 speed Road Rangers manual transmissions , thank you I know how to shift very very good myself.

Then surely you must know how annoying it is when the automatic transmission does the wrong thing, no? Or have you managed to avoid the poorly programmed ones?


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Re: Downshift before WOT? [Re: supton] #5439909 05/27/20 07:08 AM
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demarpaint Offline
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Originally Posted by supton

Then surely you must know how annoying it is when the automatic transmission does the wrong thing, no? Or have you managed to avoid the poorly programmed ones?

Agreed! There are some really good automatic transmissions out there. I find a CVT to be annoying, extremely annoying in fact. There are also a few AT vehicles I've driven that shift too soon, and at times seem to hunt for the right gear. Having said that my NAG1 AT is the best automatic transmission I've ever owned to date. It seems to do everything right. I've driven the ZF 8 speed and that transmission is excellent too. I wasn't crazy about the Ford 10 speed or the ZF 9 speed in some of the Jeeps. Sometimes more doesn't always translate to better.


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Re: Downshift before WOT? [Re: Avery4] #5439938 05/27/20 07:51 AM
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ARCOgraphite Offline
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Wife has CVT in the subaru - she wont use the paddles.

So she floors it - lets say when mergin - and the car goes to redline when all she needed to do its drop a 2 "ratios' and give it 1/2 throttle.

So In many cases YES apply 1/4 throttle moderate load then D/S then apply the load you need - then U/S.

And no cars need more than 6 speed to get on the fat torque belly - never mind 10.

In fact, 4 was enough for most 2 valvers.

Last edited by ARCOgraphite; 05/27/20 07:57 AM.

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