I have a 1984 300 D turbo. What is the appropriate engine speed (rpm) at a highway speed of 65 mph? My engine speed will be above 3000 rpm. It just feels wrong. The auto transmission is shifting through all 4 gears. I am new to MB diesels but my Powerstroke never revved that high at highway speeds.

 

65mph should be 3000-3500rpm for an 82-84 300D/TD/CD/SD.

 

Powerstroke a little bigger than 180 cu in, too!

 

If piston speeds are considered:

The 300D you're driving at 3K rpm would be equivalent to the Powerstroke at only 1580 rpm. What's wrong with that?

Don't worry. MB indirect injection diesel engines were designed to scream, and can run at top speed for the rest of their service lives without any effect on longevity. (look to the drivers of 200D's and 240D's for proof). Plus, they enjoy a generous thrashing (Italian Tuneup) once in awhile.

 

If the engine is screaming, what should the oil pressure be? Will it be pegged?

Powerstroke did have a 5 speed.

 

The oil pressure in an MB diesel should be pegged except when the engine is warm at idle and when the engine is off.

 

Please, give us your tire size and rear-end ratio.

 

I agree as well and it does feel wrong!
Yes this is the rpm's the 300D's spin on the hwy. W'ed all have improved mileage and less cabin noise would the MB engineers used a taller 4th gear ratio to slow the rpms at highway speeds and a lock up in the tourque converter. Responses are usually that the motor will last forever regardless. But I prefer better mileage and less noise!
Mileage on most 300D's I've seen is a dismal 18-26mpg and could easily have improved several mpg's would they have used these improvements that have been on American cars years before.
-Tom

 

Could you imagine.......im getting a hard on just thinking about it

 

Many know-it-all types have argued with me about this non-locking torque convertor before,
but I am older (and smarter) than they are, and I have been around the block to many times!

My 1961 190 DB had very small 650-13 tires and direct-drive in fourth gear with a 3.69 rear end ratio.
Top speed on a perfectly level road with no headwind and in the daytime was about 75 mph indicated.
RPMs were about 4000 rpm as I recall. Why daytime?
No generator was needed to recharge the juice needed for the headlights.
With only 1.9L and an advertised horsepower of 55, it did all right, for the times.

In the 1967 200D, the "dummies" elected to install (If you can believe it?) 4.10s because,
I was told at that time, that "they do so because do to the fact that the automatics
start out from rest in second gear, it was easier for the factory to simple install
the same 4.10 gears in both the automatic and the four speed sticks.
They did go a trifle bigger on the tire size at 700-13s. Big deal!
People here in the U S at that time were cruising at 80 mph.
Small wonder with those 2.0L motors being buzzed like that all the time at those crazy higher rpms.

With the 220 DCs (April 1968, new body style) MBZ went back to the 3.69s, but more
importantly, a larger 14 inch wheel with larger radial tires IF I recall correctly?
It has been about 38 years don't you know.

My last MBZ diesel, a 1999 E-300 DT, had 3.08s and a fifth gear ratio of 0.83 with 215/55R-16
radials and it still was revving much to high on the highway IMHO.
And still NO LOCKUP torque converter either .

Finally beginning with the 2005 CDIs, those "dummies" finally got smart and raised the
rear end ratio to a higher 2.65 and actually saw fit to have the T/C lockup!
Now we see people easily getting highway mileages well up into the mid to upper 30s.
Tire size is slightly bigger at 225/55-16.

Now with the new 2007 E-320 CDI BLUETEC (actually it's a 3.0L V6 motor and should
be called a E-300 CDI IMHO,) we see the newer 7G-TRONIC trannies with
seven forward gear ratios and the seventh gear ratio is a 23 percent overdrive at 0.73.
Overall ratio is now 1.9345 to one, a pretty "tall" screw to be sure.
With that tranny now locking up or engaging the T/C as has been the practice now in most
if not all automatics starting clear back in the '80s, we see highway mileages going even higher in
a fine car with even more horsepower and more importantly TORGUE! Depending on which
vehicle you research, anywheres from 388 to 400 foot/pounds (not n/m.)
That is more than most V8s.

A noted engineer once said:
"It's a heat and pressure machine. As long as it can stand the heat and the pressure, it does not care!"
Anyone know who said that?

Carry on.

 

Von Turbo,

I have driven a 1980s equivalent of the E-class. I think MB simply named it the 230E in Malaya (now the Islamic state of Malaysia). In those days the MB stick was not great particularly for a rear drive car. Very rubbery shift but fuel efficient for such a car with an anemic engine.

MB of USA will not sell this car because of an image problem and the lack of drivers that can shift and have the money at the same time. In fact, the W210 (E-class) diesel cars in Europe came standard with a standard 6 speed manual. The power. The sweet torque spot of the turbo can be maintained non-stop with the changing down of a gear whenever you like.

Is your friend rock hard yet?