LSD in a 540

[inkfish]

540i/6 comes stock with a 2.93 open diff, this ratio was used to get the mileage rating up for CAFE purposes. 3.23 is really the perfect ratio-it was used only on the late euro E34 M5 6 speed. As they are are almost none of these available stateside, the best bet is to find a 3.15 lsd (big dif) from an E32 740/750il as they can be had for under $400 and the install is fairly straightforeward. Input flanges must be swapped. AFAIK this is the only diff that fits in a M60 equipped E34.

Ben

[Jehu]

540i/6 comes stock with a 2.93 open diff, this ratio was used to get the mileage rating up for CAFE purposes. 3.23 is really the perfect ratio-it was used only on the late euro E34 M5 6 speed. As they are are almost none of these available stateside, the best bet is to find a 3.15 LSD (big diff) from an E32 740/750il as they can be had for under $400 and the install is fairly straightforward. Input flanges must be swapped. AFAIK this is the only diff that fits in a M60 equipped E34.

Ben

Very interesting.Do you know anyone or have you experienced the difference in performance with the big diff swap?I read that there could be an issue with losing the cruise control.What I'd really like to know is how much of an increase in acceleration in high gears will be had. In other words what i have in mind is being able to pass with a brief window while in 5th or 6th without having to downshift.If this ability is gained then it would be worth it to me.

[632 Regal]

you want the big unit as mentioned from a 740 or an M5, the small units from say a 530 WONT FIT. Try to go for a 3:46 or 3:64. its plug and play, no issues with speedo or cruise or anything like that. If you need to swap the side flanges its no big deal but if the front input flange needs to be swapped you better read this:

http://www.bimmer.info/~regal632/rearend.html

I did the 3:15 to 3:64 swap and its soo much nicer in the city. Im only turning around 3400 rpms @ 100 mph so theres a lot of legroom left.

[BrianH]

Brosher,
I bought my 540i/6 with the stock 2.93 open. I had the chance to pick up a 3.15 LSD cheap here in Detroit so I grabbed it. The swap is fairly straightforward. Make sure you change the input flange seal, since you have to swap flanges anyway, and put NEW LSD gear lube in. I did notice a bit of difference in the performance. Not quite as much as if you'd chipped it, but you CAN tell a difference. I definitely wouldn't go higher than 3.23 MAX for the diff ratio, or your first gear will be almost useless! The cruise control worked just fine afterwards.

[PJONG]

Since we are in the discussion of LSDs, I'd like to know what diff ration is installed in a '92 m50 520i? And can it be swapped with 3.15 or higher?