I've stumped a few MB mechanics with this one - Can u Help?
 

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.

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?

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.

If you get off on manually shifting an auto tranny, you are driving the wrong car.

i suppose that if you are going down a steep grade it might make sense to put your auto tranny into a lower gear and let the tranny govern your speed.

alternatively, i can see that if you are going up a steep grade, and the auto bogs down in drive, then it might make some sense to manually select a lower gear so as to maintain speed.

but outside of those situations, manually shifting an automatic tranny makes very little sense.

as the previous poster said, if you want to play with gear changes, buy a car with manual transmission. that means that you will not be driving a us market benz.

you will like bimmers, porsches, corvettes, though. very nice manual transmissions.

a couple of years ago, i ran a e270cdi in the alps.it had a benz slap tranny. a great deal of fun. but that is another story, isn't it?

My humblest opinion is the gated transmission was designed for a reason and meant to be shifted. Go for it and tell us what happens. Personally, I would ease up on day to day engine breaking via downshift.

Mileage comparison... we live in the city. Lots of putting about between 20 and 50. Rarely get above 50. My wife always leaves it in drive. I hold gears and shift up when I get to a steady speed. I get about 25% better mileage.

The more you shift it the more the clutches wear due to the built in slippage during shifts.

I leave my automatics alone -- the torque converter does a decent job of pulling the car down (so does the compression). I've used lower gears on grades, but that's all.

I drive a standard just about the same way, though -- engine braking isn't necessary for me, just coasting down works fine, and the auto upshifts just about the same way as I do manually excpet for the occasional use of a lower gear when I'm going to stop soon anyway.

Higher revs burn mor fuel, and dragging the engine down at high vac can cause excessive emissions (although not with most EIF systems).

I agree with most of the posters, you should be driving a car with manual transmission. Automatics should always be left in top gear (D or OD). Automatics are designed to choose the best gear for the car's speed and demand. The only exception is when the transmission is continually hunting between two gears such as when the car is going uphill. Then you switch to the lower gear to reduce clutch wear. Or when the car is going down a long incline and you don't want the brakes to overheat.

The triptonics and gated shifter designs are what I call "hollow engineering". They don't do any good for the car. They are simply there because the marketing people found they needed to come up with something for people with itchy fingers.

Fiddling with your auto gearshift is just stupid macho fantasty. It will shift better than you can. Downshifting for engine braking (note spelling) in normal traffic is one of the stupider ideas around.

I'll go along with Brian, Psfred, and some of the others. Every shift an automatic makes counts toward the failure of the tranny. With every shift some of the clutch pack and band material are worn just like the clutch disc in a standard tranny. Also tranny brake bands are just like beer or soda cans. We all know what happens when you crease the middle of a beverage can and bend it back and forth a whole bunch of times. The same brake bands will eventually metal fatigue and snap. Using the transmission to hold back a car is somewhat of an ellusion anyway. The downhill compression of the engine promotes the the continued speed of the engine by forcing the crank to continue to turn. It is really gearing that is slowing the vehicle. If you really want to use compression going down hill, you need to install a Jacobs Brake like the truckers. A Jake Brake holds the exhaust valves open to relieve the compression that keeps the engine going. I just use my brakes. They are cheap. I know this isn't an oil thread, but I will disagree with Brian on one point. I use whatever major brand is the cheapest. I think synthetics are a waist of money unless you are using them in arduous service like heavy loads or extreme weather conditions.

Peter

[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.

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.

[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.

[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.

An interesting question. I've done this for 3 years and the car is fine with it. However, I don't do it just for slowing down approaching, say, a light.. I use it more for engine braking. Particularly when approaching a bend at speed, wanting to go through the bend in that gear without the box pointlessly changing up, and accelerating out of it in that gear.


Essentially the same as a modern button-operated auto then, but with a lever instead.


It is not for everybody though.. if it feels right doing it, and you can do it well, it is very effective and nearly as good (in some cases, better) than a button-activated tiptronic/steptronic automatic.

For those that don't understand what I'm talking about, well, it wouldn't seem right to you, would it! ;)

Likewise bringing the revs up when changing down.. the abillity is there, and gels very nicely when it works.

I believe the Mercedes engineers designed all this into the cars (it wasn't sometimes referred to as the best automatic in the world for nothing). :)

As for the longevity.. changing down without bringing up the revs produces quite a jolt, which can't be good..!


peace

Russ

Schumi,

You know that you don't need to use the clutch on a heel and toe downshift in a manual transmission, particularly a crash box.

With a synchro manual box a double de-clutch isn't even necessary. I do a single de-clutch on newer synchromesh units, if a synchro gearbox is going in for a rebuild I'll many times go clutchless

As for the blip on a Mercedes automatic, I can manually downshift my automatic where the engagement is imperceptible as compared to not using a blip on the same shift where the engagement of the downshift balks.

The only issue for me on blipping an automatic downshift on my car is that because of the pedal configuration left foot braking works best. I wear a size 10-1/2 or 11 shoe and no matter how I position myself I find the height and distance between the two pedals too far apart.

I blip and it feels GREAT! I drove one of those new Bently monsters. When you push the button to downshift, the computer blips the engine for you right as the downshift occurs. I've driven several cars with the triptronic auto/stick thing, and, for me personally, the MB gated shifter is MUCh more intuitive for real world driving. The C230 is the first car that I have personally owened. As a new driver I always drove my paretnts' stick shift cars. Then my wife and I inherited her grandmother's stick shift Geo. For where we live, though, a standard transmission is just not practical. That being said, I just can't stand the feeling of coming out of a corner in too high a gear. The gated auto shifter, blending the benefits of a standard and automatic, is the best thing that ever happened to a transmission. Does anyone have proof of an MB auto box failing due to semi-manual shifting? I bet that holding 3rd or 4th for around town driving acutally saves me thousands of shifts from 5 to 4 or 5 to 3. The bottom line is I just don't care, it feels right to me. If the transmission isn't designed to work this way, then I don't want it. Good luck to everyone and enjoy!

[QUOTE=Michael Kerley]blah[QUOTE]

I agree Michael.. I also think that its effectiveness is why certain Japanese and French manufacturers have copied the shift gate.

The more mechanical feel is, in some ways, more satisfying and more like a true manual than newer electronically controlled automatics, with which you never feel like you're doing anything directly.

Russ