I have a 84 300D turbo. If I put it in Drive and go, it is a real dog for about 10 seconds. Then, after the turbo spools up (I assume) it's got adequate power. BUT, if I start out in Low, it's only got about a 2 second lag and REALLY takes off, even chirps the tires when it shifts into second. After this I shift to S (what does S stand for??) and then D.

Assuming I don't rev the engine too high, am I doing any harm by driving my car this way??
(FYI, I try to not chirp the tires going into second)

OR...if you start in D, is it really starting the car in second gear??

ALSO...what is the redline for the 3L 5 cyl diesel engine??

 

you got S and W or S and E?

Standard, you start in 1st gear but Winter or Economy start from 2nd gear.

at 6k rpm, it is still safe for diesel (just my opinion) because that's where you get the highest torque.

 

Don't think any of those years model was equipped with winter mode.
The 5-cylinder diesel had red-line below 5000 RPM, at least my 83 model had it at 4600.
I mean the highest rev the tranny would allow before shifting, since Germans don't paint the scale red.
Those transmission never have been too reliable, but forcing it into 1-st gear sounds really weird.
You can't hurt the car by shifting it manually, as long as you keep the engine below max RPM.