[yevoXF]

I have an '85 Falcon S-Pack with extractors and a 2 1/2 inch exhaust and have replaced my previous 2.37:1(i think) diff with a 3.23:1 ratio LSD expecting better take-off performance. To a certain extent it helped reduce the amount of clutch riding but now has a problem with reaching red line to fast and due to a slow synchro 4 speed manual box i believe the ratio increase was too severe... It also revs a little too high for my likeing during highway driving(2900 at 100Km/h... fairly high considering it red lines at 4500).

Since the standard XF EFI cam provides max torque between 1000 and 2800 rpm I would stick to the standard manual transmission 2.77:1 diff ratio or maybe the 2.87:1 tow pack manual diff ratio.

In an automatic though the slow gearbox wont be an issue and the severe 3.23:1 ratio may be ok... personally i gonna go back to standard 2.77:1.
Here is a list of approx diff ratios available off the top of my head

2.37:1 Standard Automatic
2.77:1 Standard Manual
2.87:1 Standard Manual with tow pack
3.23:1
3.??:1 Only get if you have a 5 speed manual(so i have been told)
and upwards

Hope this has helped...