Don't even need to rely on the tach.......1,000 rpm difference is very noticible....

Its not just a little different...its a lot different at the same road speed. And its noticible without even looking at the speedo either if you drove both.

__________________
Proud owner of ....
1971 280SE W108
1979 300SD W116
1983 300D W123
1975 Ironhead Sportster chopper
1987 GMC 3/4 ton 4X4 Diesel
1989 Honda Civic (Heavily modified)
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Section 609 MVAC Certified
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"He who fights with monsters might take care lest he thereby become a monster. And if you gaze for long into an abyss, the abyss gazes also into you." - Friedrich Nietzsche

Wonder where this is going to go if the rear is a 3.07? Only parellel that I can think of is my two 240ds both identical. One at 70 sounds like a threshing machine out of control while the other at that speed sounds normal. Or normal for a 240 as comparison with other cars is hard if not impossible. This should get interesting. Now not so sure about your glo plugs.

If you try to make a test with both wheels off the ground, the drive shaft has a tendency to remain stationary and the wheel that you are not turning will attempt to spin in the opposite direction, so, it's not usually a valid test.

I would expect the 300SD to have lower gears because it weighs more then the W123. That might make a difference, I bet the trans are geared different.

__________________
1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

How would high gear on both trans be different? They are both 1:1 ratio

__________________
-Randy Wakefield

1969 220D 4 speed (parts car)
1976 280C
1976 280S
1981 240D 4 speed (parts car)
1982 300D
1983 300TD (Ivory)
1983 300TD (gold)
1985 300TD (gray)
1987 190D 2.5
1970 280SEL (sold)
1977 240D 4 speed (sold)
1974 280 (rusted to death)
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1927 Chevy 4 door sedan
1938 Chevy 2 door sedan
1950 Willys Jeepster
1955 Studebaker President 4 door
1977 Ford F250
1979 Glastron 17'
1948 John Deere A
1960 John Deere 2010
1979 Satoh S650G
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2000 Bichon (Doby)

For example I know a 420SEL has lower gear ratios then my 300SDL. For example the 420 can carry third to 120mph and mine can only carry it to 83. The V8 has a lot more power so it doesn't need the rpms to pull a heavy car.

I am thinking the same thing, the W116 must have a solid 500lbs on a W123 so MB wants it to spin higher so the 617 can pull it along.

__________________
1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

Point is the differentials on BOTH are stamped 3.07 and the RPMS are dramaticly different on both..has nothing to do with smoothness as both are fairly smooth..didn't get a chance to check that tonight (check revolutions of wheel VS driveshaft...had lot of yardwork to do as we are getting rain tomorrow.

__________________
Proud owner of ....
1971 280SE W108
1979 300SD W116
1983 300D W123
1975 Ironhead Sportster chopper
1987 GMC 3/4 ton 4X4 Diesel
1989 Honda Civic (Heavily modified)
---------------------
Section 609 MVAC Certified
---------------------
"He who fights with monsters might take care lest he thereby become a monster. And if you gaze for long into an abyss, the abyss gazes also into you." - Friedrich Nietzsche

Problem with both wheels of the ground is the one with less drag is going to turn more.....works better with a limited slip differential............well it the rain holds off tomorrow I will check it then or if it stops for a while.

__________________
Proud owner of ....
1971 280SE W108
1979 300SD W116
1983 300D W123
1975 Ironhead Sportster chopper
1987 GMC 3/4 ton 4X4 Diesel
1989 Honda Civic (Heavily modified)
---------------------
Section 609 MVAC Certified
---------------------
"He who fights with monsters might take care lest he thereby become a monster. And if you gaze for long into an abyss, the abyss gazes also into you." - Friedrich Nietzsche

The difference you mention is in the spread of the gear ratios from 1st, 2nd, 3rd etc to Top gear (4th, 5th, 6th, whatever) which is a 1:1 ratio UNLESS the transmission is equipped with an OVERDRIVE.

To my knowledge, manual transmissions have not had an OVERdrive for a lot of years, and automatics never had them. 'Overdrive' in an automatic is usually another word for locking torque converter, for a 1:1 ratio without slip.

Best Regards,
Jim