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Discussion Starter · #1 ·
I need suggestions from you seasoned Z'ers.

I own a Datsun 240 and want to completley alter the driveline. I am contemplating using a 11 pound flywheel (NISMO)> I also have a 5 speed trans that i think is from a ZX (this is due to the fact that the tunnel wasnt altered to make room for the 5th gear) PLEASE correct me if im wrong. I still have the (OEM) 354 rear end that is spiraling downhill fast. I want to replace it with a 390 r200 diff. New mounts and U-joints of course.

This car is purely for pleasure, it really isnt a daily driver, and when i do drive i like to feel the power. I may do highway driving a couple times a year. I also plan to autocross next summer. Is this a feasable set up? And will i regret the gearing changes? I dont mind a little less streetability for better performance.

Id just like to say thanks for everyones help!!
Right on z-brothers - Evan
 

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My recommendations...

> I own a Datsun 240 and want to completley
> alter the driveline. I am contemplating
> using a 11 pound flywheel (NISMO)> I also
> have a 5 speed trans that i think is from a
> ZX (this is due to the fact that the tunnel
> wasnt altered to make room for the 5th gear)
> PLEASE correct me if im wrong. I still have
> the (OEM) 354 rear end that is spiraling
> downhill fast. I want to replace it with a
> 390 r200 diff. New mounts and U-joints of
> course.

First of all, what year 240 will determine what mods you need to install the R200. Second, 240's didn't come with 3.54:1 R180 diff, they all came with 3.364:1 R180 diffs. If you have a 3.54:1, then most likely you already have a R200. You can tell the difference between a R180 and R200 just by looking at the rear cover. The R200 is quite large and a slightly different shape. If you really want to know what ratio it is, you can remove the rear cover, and count the ring teeth and pinion teeth. Then divide the ring teeth # by the pinion teeth #, this will give you the ratio. When installing the R200, you will need the axles from a 280Z, because these are splined, instead of the 240 style which bolts to the sidegear of the R180. You will also need the 'mustache' bar from a 280 because the diff cover is slightly further back than the R180. Other than that, should be direct bolt in.

Regarding the tranny, this also depends on the year of your car. I have a 78 280Z 5spd, and did not need to cut the tunnel for 5th gear. My car is a '72, and most '72 and up do not need any cutting, regardless of whether you install a 280Z 5spd or 280ZX 5 spd. This is another mod only necessary for those with early Z cars where the diff sits further forward. (They fixed this for 1972).

In regards to your intended modifications. If you install the 280ZX 5spd, and 3.9:1 diff, your in good shape. If you're up to it, a 4.11 might serve you better, especially since you going to autocrossing and not driving the car on a daily basis. The OD from the ZX 5spd won't let rpms get too high on the highway, even with 4.11:1. A lightened flywheel is a double edges sword (see posts below). It does help in acceleration, but only when your 'on it' so to say. Off the line acceleration suffers. You will need to increase the revs you need to accelerate from a stop, and kind of 'ride the clutch' to get it going smoothly. When you shift, rpms drop rapidly, especially with a 10lb flywheel (compared to 24lb stock). You need to either have great shifting skills and/or a short shifter to make this task less taxing. I would recommend lightening the stock flywheel for two reasons.
1) It is ALOT cheaper than buying the NISMO or anyone elses.
2) You can determine what weight you want. I would recommend something like 18-20lbs. This will improve the revs, while keeping some inertia needed for off the line driving, meaning it will be much easier to drive when you're not 'on it'.
Basically a 4.11 R200 and 280ZX 5spd with the aforementioned flywheel should provide plenty of go for your application. You might want to look into some tires while your at it, as I'm sure you're going to start eating them up.

240Dave
 
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