KillerCom

Going to be in the 7-800whp mark this year. I currently have the r200 kit from Inline Pro with the 300zx differential. The current gearing is 4.08 final drive. I'm looking to get into the 3.90 mark. I have found that there is a 3.90 option for the r200, came on an Infinity. My question is, do these things simple swap or do I need to find a final drive specifically made for a 300zx diff?

Nissan R200 Final Drive Ring & Pinion Gear Set 3.916 Ratio 240SX J30 | eBay

s2000Junky

Shit, id be looking at 3.60-3.73 with that kind of power. 3.90 isnt crap from 4.08/4.10. Have you looked at a gear calculator/mph spread? You need some mph between your gears to get some movement out of the car if you plan on sticking and winning any freeway pulls.

KillerCom

I was looking for some speed by gear calculatons on this gear ratio but I came up dry. I'm not set on those 3.90's but I'd be up for suggestions from some high HP guys

s2000Junky

Yeah unfortunately ive discovered recently that the best gear calculator in general and specific to the s2k (turn0technical resources calculator) is no longer being maintained so its offline.

Your trq output and weight of the car would be the more relevant information when figuring out an appropriate gear ratio. But we know what the S weighs(not much) and how much trq a 700-800hp turbo F2x makes generally (500+) so thats what im basing my final drive input on. This is assuming your still utilizing the S2000 trans of course since you didn't state otherwise.

As a rough baseline draft, look at what some of the quickest 0-60mph+ rwd car gear ratios are running in that 500+ trq range, such as a Z06 for example. Now obviously the trq curve is broader down lower in the rpm with no lag on a z06, so that should be considered and possibly compensated for a bit with some added gear multiplication, depending on where you want your car to perform the best, but you are also lighter, which generally means you could run less gear(pulling less weight). If its all Brake boosting freeway runs though, then lag isn't really an issue, you are forcing the full beans at launch.

KillerCom

I'll eventually be running the 350z transmission

KillerCom

bump

DefSport

I have a lot of R200 experience. The 3.9x from a J30 will swap in assuming you have the same style R200 case. Every J30 is going to have a longer pinion shaft for an ABS speed sensor case (has a speed sensor on side of pinion just behind flange). A non-abs case or 4 wheel abs case like a Z32 I believe will be the same shorter length.

So matching up the length and it's not hard to swap. Just download a Nissan FSM and follow the instructions. They're actually a tad better than Honda manuals IMO.

That said, a 3.9x and Z33 gearing with 255/40-17s and a greater than 8k rpm redline is a bit crazy on speeds in gears. I was going to run a 4.08 on my Z33 box SR20VET revving to 8.4-8.6k. The 3.9x isn't much longer, but it might help you hold 4th gear a bit more.

KillerCom

So the J30 3.91 ring and pinion will in fact work with the 300zx case?

DefSport

It should work. Looking up some info and the P/N is the same on all the pinions whether it's 3 channel ABS or not. Looks like the pinion flange is different between ABS and non-ABS.

Confirmation of this, and shows difference in ABS and non-ABS diffs:

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Why don't you just pick up a J30 diff and put whatever LSD you have in it? I've done 9 or 10 R200 LSD swaps into the case, and the factory shims have always worked. Pinion height will be set by the factory, which is the real PITA thing to setup since you're pressing the pinion in and out over and over, and the side shims have always worked for me, giving in-spec backlash and ring gear bearing preload. Having done it both ways, I'd strongly recommend doing that. But keep in mind the above post by orion, who I know in the Nissan world as being knowledgeable is saying the J30 ring gear height is taller, and things are shifted slightly as a result. Honestly, I've never messed with a J30 diff case itself, so I can't verify.


One negative with that, the J30 diff will be longer by about 0.6" due to the ABS speed sensor, you need a different length driveshaft. That's if you don't already have a 3 channel ABS diff.


So yes, it can "work," it's just a question of making it all fit together.

KillerCom

So I'm going to be going with Inline Pro's new 370z setup. The stock diff runs a 3.692 ratio. I'm trying to think where I should be at final drive wise and what will, in fact, work with the R200 out of the 300zx. Again, this car will be in the 800whp range. Any input will be considered!