I'm planning on changing my ZF gears. I haven't a clue what Olthoff\Peterson were thinking when they built this ZF, 2nd & 3rd are too tall, 5th and maybe 4th are too low. So I can tell you what not to use:
4.00 final, 2.58, 1.47, 1.04, 0.826, 0.704 (1st thru 5th respectively)
Tim
I have the same gears but with a 4.22 which probably makes a lot of difference. The rev drops between gears is the important thing. In lower gears you wnat to drop intot he Tq peak, and higher gears more closely spaced towards the Hp peaks. I shift around 7k rpm, but some corners, short straight etc by definition you shift lower, so there mtoro characteristics are important.
For a street car its the opposite, you want shorter lower gears for snap and taller higher gears for cruising.
IMo for track as some say the short 1st works for getting rollling and loading on to the trailer, for the rest lower gears are taller and higher gears shorter.
After that it depends on your engine setup, where tq starts to build as well as tire height. I run hoosiers which are 25.8 ins.. My motor comes on song around 3.5-4k rpm. Sometimes I find 2nd and 3rd to be a bit tall coming out of some bends, but then i also currently have too much throttle on oversteer.
One obvious answers are to carry more speed through bends which for sure I need to do, that will keep the motor more on song by definition. After that if its still not satisfactory I will change the cam and maybe go to webbers because the currrent 580 hp at 7k rpm is more than enough, and maybe sacrificng 50 hp up top to get more TQ lower (2500-3k on) and more linear precise throttle makes for a faster car overall.
But first I need to learn how to carry the correct amount of speed through bends, which is a suspension development/setup/skill issue.
At Monticello last time we ran around 2.43. Think stock 997.2 GT3. Changing springs better shock setup(more power on stability and sharper turn in) fresh tires there is a reasonable 5-7 secs more than that. Ultimatly to break 2.30 and get into viper ACR territory, well more skill for sure, slicks, brakes, and def further suspension sorting.
Probably the gearing I have is good for track. Most areas are 3rd, a few exits second and on the long straights I see the top of 4th and some 5th. Less shifts saves time.While 5th might be short for highway cruising I am still not exceeding 160 on the straights,(current revs and tires will theoreticaly max to 180) so taller there would be slower. More important than higher top speed right now would be stability under heavy braking at the end of long straights, not over braking and carrying more speed through bends. After that, as I said maybe webbers and a flatter cam for more low down oomph and precision.
As I write this I can see in my minds eye how to loose 15 secs with the current motor and gearing setup.
So to answer the question, it all depends on tire size, motor spec and most importantly is this for street or track..