LSD gearing ratios

[SRdave240]

disclaimer - I have searched and could not find info on this specific question

What are the pros and cons of the J30 (~3.9) and 300zx (~4.1) rear diffs on an SR20det swapped daily driver.

I know the 300zx will give me a better standing quarter mile time. Will the J30 be faster from a roll? Which will be more streetable? Which would be better for autoX and road racing?

An interesting note is that the ratios for the 300zxTT are closer to that of the J30 - is that better for boost?

thanks

[Nathan]

The 300zx diff will give you faster acceleration all around, both from a stop and from a roll. However, the J30 will raise your top speed a small amount but more importantly (at least I think) it will drop your cruising rpms...albeit not by much. Mostly the benefit is just from getting a limited slip differential in there, the gearing is so similar that it doesnt matter much IMO.