Starting a new project...Subaru STI Differential swap into my Z

[Hunter260Z]

Zedyone

What's your gas milage with the 3.90 on the highway. Mine gets around 27 mpg.

[ZXR616]

Drove to Nebraska in August for the Sand Hills Open Road Challenge, 2600 miles round trip...got between 22 to 24 at highway speeds (80+). Sure wish I had cruise control!!!

And I was towing a trailer!!

Edited October 29, 2013 by ZXR616

[Hunter260Z]

Zedyone

I have 4 speed trans and 3.36 diff.

[Zedyone_kenobi]

I am not sure buddy.

I have not finished this mod yet. I have just ordered parts.

UPDATE:

Wolf creek half shafts are ordered and on the way.

All parts should be here in about a week!

When I get them installed I will see what kind of mileage I get Ray.

But I bought this ratio with the intent on one day maybe putting in a Datsun 5 speed.

[Travel'n Man]

Keep us updated - the 5 speed is the way to go if you do any traveling at all. Slipping in 5th gear a 60MPH is a beautiful thing.........and still have plenty of get up and go! My 3.90 diff is great through all the gear changes with the 5 speed. Putting in a 4 speed with the 3.90 may be a little over the top........fyi.

[Zedyone_kenobi]

Well I can start out with the 3.90 as it is, and then if it gets too bad, I can install a 5 speed. I already have the tunnel cut, and the console modified to accept the Type B. So it should be a breeze. Still I mostly just put around doing car shows locally within 20 miles. So it may not be too bad. The occasional track day as well.

Still the new diff may make my dieing tachometer a bit more of an annoyance. Time will tell. I can see mostly good coming from this.

[Hunter260Z]

I thought someone came up with a modified shift lever that would save a lot headaches.They even had a picture,looked pretty neat.

[Zedyone_kenobi]

It exists, but I am actually using a stock B type shifter in my car. I had to trim the OEM 71 console a bit, but it works wonderfully and you cannot tell I made the cuts.

[Hunter260Z]

That's great,The older I get I find my memory failing me. By the way, what motor did you get from Datsun Spirit. STR2.8a or STR2.8b

[Jeff G 78]

I like the upgrade and I understand that you are getting a modern, good condition diff, but wouldn't finding a low mileage R180 or R200 and installing an OBX LSD be a cheaper option? It's not a shot at you, I'm really asking which is better/cheaper. Here in the east, there are countless rotted out S130's with low mileage 3.90 R200 diffs. The OBX sells for about $400 and the S130 R200 can be had for nearly nothing. I paid $500 for an F54 engine, 5 speed trans, 3.90 R200, driveshaft and halfshafts all with low miles.

[Zed Head]

With the OBX you'll have to get deep in to the guts of the differential, and the odds are high that there will be clunking or howling or the Belleville washers will fail if you don't replace them. With the STI you could not even remove the cover and probably end up okay. Kind of comes down to how much risk you want to take and how much wrench work you want to do. The OBX seems simple in concept but the details are difficult.

On the 5 speed - don't forget that the early ones have a 3.321 1st gear and .864 5th, while the later ones have a 3.062 1st, and .745 5th. The later ones, 80-83 ZX, typically came with the 3.9 rear gear, so you'll want an 80-83 ZX 5 speed.

[240260280z]

Never heard of the OBX (apart from the synth).

Looks like OBX is of typical mainland China quality metals, quality build and consistent component uniformity...

OBX_LSD Products

Remember they can polish a turd there very well.