what diff ratio for better take off speed?

[thrasher_ryan]

hey
I just bought a standard '87 XF Falcon and its totally gutless off the mark and im looking at getting a better diff but i have no idea what ratio to get or what will fit it.......
im also getting ....extractors
2.5 inch exhaust
lowering it
mags
thanks any help or ideas are good

[thrasher_ryan]

[hey ive had this question posted for like 2 weeks and noones replied me
cum on i need some help
cheers

[PR_Jr]

I am not sure which ratio's are available for XF diffs, but you need to get "lower" gears.

ie. If it has 4.5:1 gears you want a higher number such as 5.2:1 for better take off.

However, better take off will result in lower top speed, but seeing as you only go as fast as 110 k/mh you will be fine

[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...

[oldschool muscle]

Like he said, if these cars make all they're torque down low then maybe you'd be alright with your stock gears. I still reckon you should go higher though, generally higher means faster quarter times.