lvduke

Driving my wife's all original 1989 300SE inline 6/gas at 60 mph I noticed the rpms at a little over 3000. This rpm seems high to me when I would expect the transmission to be in overdrive. The automatic transmission seems to shift properly. The local MBZ mechanics are unable to answer this question after test drivng it. Does anyone out there have a clue?

gsfent

From memory, my friends old 89 TE turned similar rpms. The car is geared a little stiff IMHO because the motor does not have a ton of power. So to make up for it, MB uses gearing. If you can tell me the real diff ratio (prob around 3.07), the tranny ratios and the tire size, I can post for you, or email to you, the speed in gear at various rpms.
Regards,
Jerry

lkchris

It's normal and there's no overdrive.

Our '88 300E with same engine turns 3500 at 75 mph

Our '06 E320CDI turns 2200 at 75 mph and will accelerate from that faster than the W124.

lvduke

Thanks for the input.

I tried to locate the information requested but did not have much luck. I did find that it's a 124 chassis, the automataic transmission is a 4 speed, the rear axle ratio is 3.07:1, and the trans starts out in 2nd gear if not floored - apparantly this feature was an fuel conservation measure implemented for the 1989 model.

I test drove it to again check out the shifting steps: with easy starts - presumably in 2nd gear - I felt 2 shifts suggesting that it went from 3rd to 4th gear. But when I floored it to engage 1st gear, I also only felt 2 shifts, suggesting that it stopped shifting when it reached 3rd gear. All driving done on flat streets - no inclines.

Any further thought/comments would be appreciated!

lkchris

Not really "implemented for 1989" as all previous W124s (USA) featured 2nd-gear start.

1st in these cars is a bit of a stump puller anyway, as all European cars must pass the "pull a house trailer away from a stop up a hill" test mandated in Switzerland.

You know, it takes a certain amount of power to do a given amount of work and it takes a given amount of fuel to produce that power.

A 180-cu in engine like your W124 is going to have to rev higher than some 350-cu in American iron to accomplish the same thing. If you made it 180 vs 360 it would take exactly twice the revs to accomplish this ... theoretically, that is, as cam lift and timing would have to be identical, etc. Of course the American car is likely to be heavier and perhaps not as aerodynamic as the W124, too, but perhaps you get the idea.

Had your W124 been turbo- or supercharged, the system might cram 350 cu in of air into 180 cu in space and fuel flow increased to match and then perhaps your W124 could turn lower revs. That's the way it works with our turbodiesel E320CDI (plus the fact diesel fuel contains more power per unit than gasoline).

The idea is ... don't expect things to be the same with a Mercedes as you may be used to having owned other cars.

lvduke

Points well taken. Thanks for the input. You are absolutely correct about Mercedes not being like any other car. A fact I continue to learn more each day.

I must conclude that 3000 rpm at 60 mph is normal for this car.

Peculiar that my Mercedes mechanics didn't have a clue. Time for new mechanics!

j.wilhite

my 91 300 e is exactly the same
3000 at 60 i have a 2.6 really hard to tell when it shifts
to smooth butt my car has hit its redline with no problem
just do your maintence and you will have no worries