Wow!
What an interesting bunch of responses. One thing is for certain here, we all are individual in our thinking and as we live in democratic societites we are free to do what our finances allow.
One Mod that no one mentions is the alternative ratios available for the diff.
Most 840's have a 2.93 ratio which is great if you live in a country where you are able to use a freeway without cops or camreas and like MACH1 speeds.
Alternatively if you wnat to go form 0 to 100 in less than 6 minutes then a higher numerical ratio is a consideration as is an LSD centre.
I changed mine to 3.64 which is the standard ratio on the v12's with 4 speed auto. I notice a small decrease in fuel economy but the car now feels like a fast car. Havent done a quarter mile elapsed time and dont intend to as Im not a racer (well, not most of the time anyhow). I can tell you its a very worth while swap and every v12 owner that has driven my 840 is most impressed and the usual question is what ratio can we use to do the same in the V12.
This is a (partial) list of available ratios for the V12/V8 diff that was common to E31/2&4 cars
2.88, 2.93, 3.15, 3.23, 3.46, 3.64, 3.71, 3.9, 4.17.
LSD centers you may ask? Well the dumb assed way in wjich BMW controls wheel spin is the ASC which retards engine power which means if you are a performance driver you cant go around a corner without the ASc cutting in and reducing power just when you might wnat it. The answer is to have LSD and overide the ASC when you dont wnat it to kick in.
LSD centres are not common and can be installed to any ratio (by a competant diif shop.
Any one interested, I know where there are 3.23, 3.15 and 4.17 LSD's laying around. I would be happy to broker a deal and send internationally by post.
Maturing Disgracefully