best rearend ring pinion?

[XTCshri2222]

i'm buildin my car for drag and autox. I'm planing to swap out the ring pinion gears. i was thinking about some 4.6xx gears to replace the 4.08 also came across some 5.1xx gears made for a nissan trunk r200, i'ed figger it would fit but would it? And whats the best ring gear to use? I know the CA is supposed to have a 4.36 instead of the 4.08 I have. Whats the best? I'm tring to build a rear end, I also have access to a 89 300zx n/A VLSD but I dunno what gear they run.

[float_6969]

To try and build a car for drag AND autocross is going to be hard. The build specs for those two types of cars couldn't be farther apart.

What I CAN tell you is that I built my car for autoX and I went down to a 4.363 in the diff with a Helical Diff and it's a great setup for the cones. I haven't ever run out of gear, and I haven't ever had to down shift.

There were a couple of times in an autoX with a sharp 180, or a series set of 90's that I had to downshift to 1st with the 4.083. I don't think that will ever be a problem for me again.

As for drag, it depends on what kind of ET's you're looking for. If you're running the 4.363 diff with the stock CA trans, you're gear limited to about 145MPH @ 7500RPM in 5th. 145mph in the 1/4 mile is about a mid 9 second car if I had to venture a guess.

The problem with that diff and trans setup, (and this is from experience), the revs on the highway are pretty high. I run about 3300-3400 RPM at 70mph on the highway. It's not real great for gas mileage.

Just some stuff to think about....

[UMS_CA18DET]

If you truly want both Autox and Drag than I suggest looking into a better motor. With the CA its either one or the other, unless your looking for something like Mid 12's.

For less money your gonna spend to make your car for Autox and drag you would be able to accomplish by just swapping a LS1. LS1 with 6 speed T56 can be had for $3500.

[Kouks]

4.363 rear end is what I would pick for auto-x or drag really, it should keep you from having to go in first in auto-x, and will improve acceleration. 145 at 7500 is correct. Imagine if you had the turbo and the valvetrain to go higher, 8500-9000k rpm would be very fast.

Mazworks runs an SR, but besides that they run a 4.6 rear end, and run 9.2's at 155mph. 998.6whp! Straight drag.

[XTCshri2222]

alright thnx, i'll go with a 4.363, i'm more autox not shifting into 1st or having to shift is best. As far as drag i'm just lookin to be a mid low 12 sec bracket car.