I'm on my 7th MB, and somewhere along the line I've developed a strong habit of treating my automatic transmission almost like a manual. For the sake of conversation, I'll use my 95 E320 as an example - Bottom line, I shift between 'D' and '3' a LOT. On a fifteen minute drive I might shift back and forth a dozen times (to help decelerate at traffic lights, and occasionally for faster starts). Sometimes I'll even use ALL the lower gears (in the case of the 95 E320, that would just mean 3, and 2) to help decellerate.

Here's the question:
Am I saving wear and tear on my brakes and possibly helping fuel efficiency, or am I putting dangerous, useless wear and tear on my A/T? If there is no clear answer to that one, perhaps you could just answer this - do you think it is a BAD thing, or would you guess it is mostly harmless?

Any opinions would be appreciated - the more educated that better!

Thanks for reading - thanks even more if your respond!

Brake pads are cheaper than transmissions.

The more you shift an auto tranny, closer you come to replacement!

You are saving wear and tear on your brake pads, however you are not helping fuel efficiency.

That being said, on downshifts, you are wearing the clutches in the transmission in lieu of the brake pads. The brake pads cost about $50. to replace. The transmission costs upwards of $1500.

On upshifts, you can hold the transmission in the lower gears for an extended period if you feel the need to do this. There is very little additional wear caused by a delayed upshift.

Around town, I frequently hold the SDL in third gear all the time, provided that the speed stays below 35 mph. This prevents the upshift to fourth, which is practically useless because of the next upcoming traffic light. It's probably not as practical with gears above 2.88, however.

do you make any attempt to match revs on your downshifts? a little blip of the throttle to match that 1000rpm jump as you flick into the lower gear.

sounds like your shifting on the rounds to the grocery store which is linkage wear and as you have seen by talking to the mechanics the A/T wear issue is more complicated, your car shifts gears and if you do it manually why should that hurt more? also the car has a fluid coupling between engine and gearbox which could soften things.

Gearboxes are pretty good at doing there job, holding a gear manually for better acceleration can gain a few-tenths depending on set-up.

If a downshift is needed in addition to full braking to slow the car to avoid a shunt that's cool. or if a downshift is needed to get throttle response in a turn or out of a turn or while doing some trail braking that sounds reasonable to me.

A lot of automatic transmissions have either lever or pushbutton activation on their steering wheels for manual changing, Mercedes is one manufacturer that does so.

Your car lack the failsafe computers like the other manumatics so your brain needs to show mechanical sensitivity and reasonable A/T maintenance.

If you choose the proper times and method for manual shifting it can bring much enjoyment.

Also consider some books, Vic Elford High Performance Porsche Driving for instance to learn how and when to shift.

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Living in a montaneous region, the shop manager at the M.B. dealer recommends to downshift manually to avoid constant braking (hence saving brake pads). The owner's manual on my cars also mention this factor.

I do manually downshift on my E 320 T, which works fine as long as the speed is correct.

On my S 500 L I am constantly amazed everyday: I leave the electronic 5-speed A/T alone at "D" and when going downhill it will AUTOMATICALLY downshift (up to 2 to 3 gears, depending on speed) to provide engine braking, saving brake pads.

Hence: why if it is inappropiate to downshift an automatic transmission due to clutch wearing, the electronic program on my 722.6 does it, and does it so remarkably well?

Any thoughts?

__________________
A. Rosich
CL 500, 1998
S 500 L, 1998
E 320 T, 1995 [Sadly sold ]

I believe that you might be confusing two things:

1) The desire by M/B to have the driving experience for the driver simplified to the greatest possible degree. Downshifting the transmission for the driver will serve this purpose and thereby require the driver to utilize less braking force. The driver is amazed by this technology and appreciates it.

2) The desire by many of us on the forum to maximize the life of every component on the vehicle. We will do everything possible to ensure that these machines will last far beyond a "typical" lifespan for such a vehicle. Changing the oil at 3K intervals using nothing but the best synthetic oil money can buy, changing all fluids religiously, monitoring oil pressure and water temperature within several psi or degrees of temperature, all point to individuals that desire a vehicle to provide long term durability. This is in direct contrast to the function of your 722.6 transmission, whereby the driving experience is the sole factor utilized by M/B when determining the shift patterns.

Hey I do the same on the C230 722.6 and E320 722.4. Not really on the down shift to add breaking (unless you've got a racing bug and budget, why do it?), but more to hold the engine speed where I want it. On the 722.6 for normal around town driving, I'll often leave it in 3, moving to 4 or 5 only if I get up to a steady speed. For deceleration, say I'm crusing at 65 but then traffic slows to 40... move from 5 to 4 with a slight throttle blip, and have the engine, without a downshift delay, at the perfect speed to accelerate. On the 722.4 I hold it in 3 and move to 4 at speed. If I'm really putting about, (and once I'm past 1st gear) I'll move to 2 as needed. Talk about power coming out of a slow corner. I personally think this method gives superior fuel mileage, and is WAY MORE FUN.

__________________
Michael

1988 300 SL (5 Speed)
1994 E320 Wagon
1997 C230

[QUOTE=Ethan]do you make any attempt to match revs on your downshifts? a little blip of the throttle to match that 1000rpm jump as you flick into the lower gear.[QUOTE=Ethan]

I don't think this makes any sense. On an automatic, blipping the throttle doesn't match revs because the engine and transmission aren't diengaged like in a manual with the clutch depressed.

And like many people say, by constantly shifting your auto you are increasing wear on transmissions (several thousand $ to replace) to extend life of $50 brake pads. That said, I will manually shift my 300E sometimes because in D it is too slow to downshift and doesn't hold gear long enough when you are trying to drive quickly in city traffic (where you can't just floor it in each gear because you have to keep slowing down and speeding up to go around slower cars). My other car (Porsche) is a manual and my 300E is the first auto trans car I've owned so it is just a habit.

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2005 Mercedes C230k sport sedan, 6 speed
1987 Porsche 924S - 968-engined track car

Get yourself a first gear start kit intsalled.

As far as an automatic goes, my limited opinion is that you're not adding much wear to the transmission itself but the shift linkage is the big additional wear point.

As far as engine braking goes, its a matter of cost, brakes are cheaper (and easier to work on) than engines/transmissions. Another view is I can periodically change brakes in an evening without being without a car, but engine/transmission work is usually a lifestyle change.

__________________
5 speed '91 190E 2.6 320,000 mi. (new car, fast, smooth as silk six, couldn't find any more Peugeots)
5 speed '85 Peugeot 505 2.5l Turbo Diesel 266,000 mi. (old car, fast for a diesel, had 2 others)
5 speed '01 Jetta V6 (new wifes car, pretty quick)
5 speed '85 Peugeot 505 2.2l Turbo Gas 197,000 mi. (wifes car, faster, sadly gone just short of 200k )
5 speed '83 Yamaha 750 Maxim 14,000 mi. (fastest)
0 speed 4' x 8' 1800 lb Harbor Freight utility trailer (only as fast as what's pulling it)

[QUOTE=schumi][QUOTE=Ethan]do you make any attempt to match revs on your downshifts? a little blip of the throttle to match that 1000rpm jump as you flick into the lower gear.[QUOTE=Ethan]

I don't think this makes any sense. On an automatic, blipping the throttle doesn't match revs because the engine and transmission aren't diengaged like in a manual with the clutch depressed.


My reply, Do a test, drive in fourth gear at 50mph, while maintaing that speed shift into third gear, what happens?

In my car the engine revs jump approximately 1000rpm.

in my 722.6 transmission the gear changes in 4,3,2,1 are transmitted elwctronically.

Now let me quote from Vic Elford's Porsche Driving book page 101
"Heel-and-toe Shifting with Tiptronic"
many of you who now drive 911's or 968's with the Tiptronic transmission are probably wondering if you can apply the same technique -i.e heel and toe of a manual transmission.- The answer is yes.
You already know that when changing up you can do so at full throttle with just a tip forward of the gear lever so that there is no lost time in acceleration. When you are changing down you will find that you can actually feel the electronic contact as you "tip" the gear lever backward. The "blip" should be done at precisely that moment to balance engine and transmission speed. It mght take a little time to develop the feel for that electronic contact because it is very delicate, but it is there." end of quote

now that I have quoted, I used to drive a 1991 911 Carrera 2 tiptronic where I learned the technique and it works on the Mercedes box as well as the four speed ZF Porsche unit.

As far as mechanical sympathy and wear, you can reduce speed every time the steering wheel is turned to minimize tire wear, never start the engine when it has been sitting in sub-freezing ambient temperatures. Figure out BMEP - brake mean effective pressure and fuel consumption effective usage and only run the engine at that derived rpm.
But the great thing about Mercedes is they cruise at speed like no other, and now that some of these cars (New SLK 350) handle like a Porsche Boxster and are built much better, if you know the pros and cons to enthusiastic driving then have fun.

Do you buy a Ferrari F40 and not flog it? a little to much excitement a missed shift, a spin, a few over revs.

What does your manual say?

Mine says don't do it.

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2002 E320 4-Matic
2008 Subaru Outback
2009 Subaru Forester

[QUOTE=Ethan][QUOTE=schumi][QUOTE=Ethan]do you make any attempt to match revs on your downshifts? a little blip of the throttle to match that 1000rpm jump as you flick into the lower gear.[QUOTE=Ethan]

I don't think this makes any sense. On an automatic, blipping the throttle doesn't match revs because the engine and transmission aren't diengaged like in a manual with the clutch depressed.


My reply, Do a test, drive in fourth gear at 50mph, while maintaing that speed shift into third gear, what happens?

In my car the engine revs jump approximately 1000rpm.

QUOTE]

Of course the revs will increase because of the different gear ratios between the two gears. With a manual trans you blip the thottle on downshift so that when the clutch reengages, the engine is already turning at the speed it will be turning for given road speed in the lower gear so there is no jerk as the engine comes up to speed. I don't think the printiple applies in an automatic, which lack a clutch between the engine and trans (it does have clutches w/in the trans). But I haven't driven a porsche with steptronic (because I think automatics in porsches are a tool of Satan), and I know the last Panorama one article describes various shifting techniques for use with them.

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2005 Mercedes C230k sport sedan, 6 speed
1987 Porsche 924S - 968-engined track car