S-Class Guru,

I say go for it. I recently changed the diff in my 1984 399SD from a 3.07:1 to 2.47:1. Although my 0-60 time increased by 2 seconds (was 11 sec, now 13 sec), the car does not "feel" any slower than it did before. Driving down the highway it feels like a totally different car - it is very quiet and relaxed.

I guess I should quantify my thoughts on acceleration. With the 3.07 diff, I always thought the car was slow. I never raced cars away from stop lights - what's the use? I thought the 2.47 diff would really bog the engine down, but it didn't. Granted, mine always starts in 1st, but you would have a hard time guessing which diff I had in.

Before Thanksgiving (and before I switched the diffs) I drove 1600 miles Chicago -> Mississippi and back. While it was physically comfortable to sit in the car for 12 hours at a time, the engine screaming at 3500rpm wore me out. With the new diff, the engine turns 2600rpm @ 70mph.

As far as the speedo, there are several "black boxes" that can take the current speedo signal and step it up or down to give you a correct reading. They cost around $100 - if you have the ability to change the diff yourself, you should be able to program the box.

I say go for it. If you don't like it, you can always change it back. Everything is easier the second time around.