Rear differential question
Ok, I'm slightly confused about my rear differential. I have an '86 300E with the m103 engine in it. Now, when cruising around it tends to hum along in pretty low rpms (averaging 2000-2500 or so), but when I'm on the freeway it hits around 3500 doing around 75mph. This seems kinda high to me, I wasn't sure if I had the stock rearend in my car, or what the ratio of it is or anything. I'd be curious to know what rpms everyone else runs at with the same model type, or if anyone knows whats going on with mine. I just got my car a month or so ago and its taking some getting used to... one thing I noticed is that it loves purring in the low rpms, it cruises in 4th gear almost all the time. When starting from a stop it starts in 2nd, hits 3rd for a half a second, then immediately kicks into 4th. Is this normal operation? It doesn't complain or have any trouble, it just seems weird. Just curiousity...