Arrie

Who the hell is the manufacturer saying it is ok to keep engine in red zone?

Arrie

Engine braking is not bad for the car. Transmission normally pulls forward and wears gear wheels and bearings in one direction. During engine braking the direction of forces changes to opposite so you use the opposite side of the teeth on gear wheels as well as it changes the bearing in the end of each shaft that carries the axial forces that helical gears generate. The only parts that do not see this positive effect from engine braking are the clutch packs.

Left Coast Geek

i have tried using manual mode on twisty roads and grades, I find that 1-2 downshifts doesn't provide that much engine braking with the M276 NA35 engine. Under the same sort of road conditions, I like "S" (sport) mode, it delays upshifts and generally makes the car more responsive, and also smooths out low speed off and on the throttle transitions where E mode might prematurely upshift then have to downshift again.

BenzV12

Yes, I do but when in comfort mode I don't use them that much

kajtek1

Clutch pack is not moving during engine braking, so it doesn't car what you do at this point.
It is the shifting that wears them, but again, computerized system matches rpms , what is minimalizing the wear.
Obviously sport mode will do shifting at higher rpm, what speeds clutch wear.
But I don't think average owner will worry about transmission lasting 300k miles

Arrie

During engine braking gears are also likely changed so the clutch packs do see some wear but the forces in general are smaller unless you slam it from 7th to first very fast.

And exactly what “computerized speed match” are you talking about?

kajtek1

If you pay the attention, during slowing down, you will notice the tachometer will jump up several times before you come to the stop, while it is hard to notice and braking surges.
This is your computer adjusting the engine speed during gear shifting. Not only for comfort, but also for longer clutches life.

bmwpowere36m3

Older boxes downshifted fine, the problem was most were rolling on high-mileage, due for overhaul units. Or the typical "hack" was to increase the modulator pressure to mask worn clutches and resulted in jerky shifts. They were slower in shifts and if you accelerated hard and let up, it wouldn't be crisp.

Kevin Brod

Thanks for all of your input. The automatic doesn't brake the car too much when auto downshifting vs. manual though. So you answered part of my question, which I suspected, that downshifting to brake puts additional strain on the transmission which will send it to the shop quicker. I would rather pay for brakes and pads than a new tranny for sure!

kajtek1

Once again, transmission can take braking strain just fine and driving heavy Sprinter, I don't hesitate to drop 3 gears and have engine close to red zone on tachometer.
Just try to avoid shifting under the strain as that is what will shorten clutches life.
Than again, how much you worry that transmission will last only 200,000 miles instead of 300,000 ?

Arrie

When you slow down and gear changes down the engine speed jumps up just because the lower gear required the engine to turn faster. There is no other speed match than what the clutch pack does when it engages.

The only clutch with speed match is the TC locking clutch. It will not engage before the transmission speed is close enough to the flywheel speed.

BenzV12

I have a question though related to manually downshift effect on the tranny wear and tear .Well, In Sport Mode when you hold the ( - ) button to downshift the car downshifts more than 1 gear of speed . Let's say you are cruising at 6th gear in Sport Mode , you pull and hold the right paddle to be more quickly accelerate and then the car just downshifts nor just 1 but up to 3 gear to respond your demand .Well, do you think this would put more stress on the tranny or it wouldn't matter as everything is electronically adjusted

kajtek1

Do you feel car jerking when downshift happen?
Read the discussion above, those cars have computer adjusting engine rpm to match transmission speed, what minimalize clutch wear.
Transmission is design to take the stress.

Left Coast Geek

I doubt it is any different from whomping on the throttle and causing it to automatically downshift the same number of gears.

Arrie

Engine speed would need to adjust between the time when the higher gear clutch opens and the lower one engages. My understanding is that at gear change the clutch packs work together so that both are "partially" engaged with lowered friction so that there is no jerking when the gear changes. I don't think it is possible for the engine to match any speed on its own as the speed must change with the clutch pack engaging.

Left Coast Geek

if the engine simply momentarily lightens up on the throttle, that greatly smooths shifts.

the Ford 10 speed truck transmission doesn't even disengage the torque converter lockup once its rolling, it does all shifts with just the gearbox and electronic throttle. The 10R140 is rated for 1400 Nm or 1000 ft-lbs.

BenzV12

I think you would not like to make its presence felt thru gear changes given number of gears in the tranny ,so smooth shifting is verily required here

ClasseMiaMadra

I found that it's easier to use the accelerator pedal to downshift instead of the flaps because the transmission still stays in full auto. To downshift if preparing to pass for example, I dip the accelerator momentarily and that down shifts immediately, equivalent to using the flap or stick shift, so now in the lower gear I step on it as needed to pass, or otherwise accelerate, or to be ready for the next tturn. I always drive in sport mode btw. Haven't used the flaps since I adopted this method.

Arrie

If you really want to make a quick pass you hold the left paddle down for 2 seconds. This puts the car on gear that will give you the the best gear for acceleration at the speed you are going. Then after you floor the gas pedal and get passing the car you hold the right paddle to bring the transmission to the normal highest gear mode.

Just flooring the gas pedal down shifts but it seldom gives you the best gear for acceleration.

nateo83

i found holding the left paddle is great for downshifting when coming to a stop or approaching a traffic signal queue. Have not thought to try it when passing. I just coded in full time manual mode and agility, I found it extremely frustrating when trying to pass when I wanted the power and the car up shifted and the pedal was dead.

Now interestingly I have full time manual if I want it, but if I’m in an automatic mode - E, S, or A - then it behaves in this semi-automatic mode where it flips to manual and then back. If I want full time manual I need to use the mode select button.

I just came from driving a manual with 6 gears and so I do dabble with the full time manual mode - but it’s not the same. If the paddles were stationary instead of turning with the steering wheel they would be more useful for full time manual. Nothing worse than rounding a corner and having them backwards when trying to use them.

Left Coast Geek

huh, especially in S mode, but even in E mode, I find if I just roll on the gas hard, it shifts down as many gears as it needs to get the engine RPMs up in the 4000-6000 range where the M276 3.5 just zooms. if I don't let up pretty quick, I'm blowing past 105 MPH before I know it.

Arrie

My car does not down shift enough for the best performance by just stepping on the pedal but holding the left paddle works every time. My problem with using the paddles is that I cannot hear the engine and I end up red-lining the engine almost every time I use them and I don't like that because the red color in the tach is for a reason. So, I very seldom use the paddles as I very seldom drive on 2-lane highways where you need the quick pass but sometimes it happens and I can tell my E550 becomes a rocket ship when doing the hold on the left paddle. It is just unbelievable what performance this car has for a 4-door sedan...

kajtek1

I guess this come from driving 21 and 44 HP cars, but I never depend on car acceleration for passing.
When on busy highway, I follow slow car with some distance and when I see space to pass coming, I start accelerating some time before the space comes.
Meaning at the time when car from other direction passes us and I have some space, I am right behind the slow car, already having ca 20 mph higher speed, so it takes 3 seconds to go around slow car.
Most of the time I have no need to accelerate more after lane change.