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i have 3.7 diff ratios what would i need to do to give car longer legs thanks

You can't get a taller ratio in a Subaru. If you want to make the ratio higher then all you can do is fit a taller tyre.

Hmm, you hear about the Datto kids modifying Subaru diffs to suit their 1600's. Maybe you could get a taller ratio out of a 1600 (which is also an R160) and modify that?

Are you just wanting better fuel economy? Maybe you could look at engine modifications etc?

The problem there Tim is the dato's are RWD in the suby you would still be stuck with 3.7 in the gearbox for the front wheels.

Jordan.

so fitting 3.9 ratio would not effect the speed to engine revs i am not sure how the ratios is it 3.7 turns of the motor or the diff ?

A 3.9 would make your revs about 200rpm higher than with the 3.7.

Jordan

BaronVonChickenPants wrote:A 3.9 would make your revs about 200rpm higher than with the 3.7

ie - give it "shorter legs"

The longest ratio I've ever seen in any R160 rear diff is 3.54, from a Liberty RS, but these ran a 3.7 front diff and a reduction drive in the gearbox. I've messed around with a few Datsun 1600's too, all I've seen have run a 3.7 final drive. Remember R160's only come in the sedans too - wagon 1600's have a live axle!

You could run the 3.54 ratio with a RWD conversion, I did this for quite a while, but it's very overrated. I found the EA81 didn't have the horsepower to accelerate on that ratio, the final drive is 3.7 for a reason

R160s are pretty much the most common IRS diff in Jap cars - Everything from the mighty Datto 1600 have them up to 180SXs and some Skylines. They're even found in the front of some Nissan pickups. As a result there are loads of options here.

The problem would be finding a high-ratio front diff to match it.