r200 390 vs 370

[240zprace]

which one would you use??? for all around driving and sometimes off to the drag strips. 280-350 rwhp. plus tell me why you would use that one vs the other........

[JMortensen]

You've got to look at a combo of factors: where the engine makes power, trans gear ratios, rear gear ratio, tire size. If you have a V8 or a turbo L6 that doesn't want to spin higher than 5500, you'll use taller trans gearing, taller rear gears, taller tires, or a combination. A high rpm V8 or a NA L6 that makes power from 4-7000 rpm is going to use lower gears. Also depends how you use the car. If it is a daily driver the primary concern might be freeway rpms. For an autox car, might be to keep the rpms high on slow corner exits. For a drag car, probably the most important thing is the trap rpms. Don't want to run out of gear and hit redline 200' before the line, but you don't want to chug across at 3500 rpm either.

 

I have had the 3:70s for years and they were great when I had SU's on my car, but when I switched to triples they were an immediate problem. In my case I just bought a 4:11 and I'm going to swap my LSD carrier into the 4:11. But that works for my high rpm NA L6 at autox, and might not work for you.

 

It's all about your setup and what you're doing with the car.

[Phantom]

I ran 3.90 in my Z with the L28 and it was great for the NA motor. With th eLS1 (311 rwhp) and the T56 I'm running the 3.70 LSD. I would consider that even a bit high. A 3.54 or 3.36 would be better as 1st gear on the T56 overwhelms the tires with the 3.70. It is great in the other gears though!