hello..
would a 3.9 diff be ok on a 2wd cosworth road car or will rev its tits off at say 70 mph... anyone have any experience..?
thanks..

 

u would lose some top end i dont how much not massive amounts i dont think and it will accelerate faster id stick with the 3.64

 

If you want I can work it out exactly for you, just confirm what tyre size you are using.
tabetha

 

The std diff 3.6, gives 23.2 MPH@1000rpm in top gear(0.80), with a 205/50x15 tyre
The new 3.9 diff gives 21.4mph@1000rpm top gear with same tyre as above.
Hope this gives an idea, so std diff gives 69.8mph at 3000rpm, 3.9 diff gives 64.2 at 3000rpm.
tabetha

 

ok thanks for that.. im running 18s 215 35 18 .. ive seen one for sale with this ratio that was all.. think the std one is a pain at 70mph with high ish revs dont want it any worse...
cheers..

 

That tyre size gives 22.2mph/1000rpm in top(0.80) 2wd box.
tabetha