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What front diff do these cars run ?

I know the rear diff is a Fuji Industries R160, or in the STI an R180.
The Skyline GTRs also run an R160 in the front, and there are quite a few options for aftermarket diff centres for the GTR.

Front diff is actually integral to the transmission. FWD axle shafts come out just rear of the bellhousing I am not sure if it shares any parts with a common diff or not but I doubt it.

Cheers.
Cory

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Build log: viewtopic.php?t=9291

Cory, there is still a crown wheel and pinion, and a front differential in there, and it will be a standard size.

As a matter of interest Fuji Heavy industries make diffs for every car manufactured in japan, except Toyota and Honda.
Toyota and Honda make their own diffs "in house" and are therefore unique designs.
Fuji also own Subaru 100%, so the front diff will be made out of standard Fuji bits absolutely guaranteed.

That means Subaru, Nissan, Datsun, and Suzuki internal diff parts (of the same sizes) will all interchange.
These all use identical R160 centres with 25 spline axles. There are many ratios, and both directions of rotation are made. I have several R160 diffs here, and am very familiar with them.

An identical situation exists in the US with Borg Warner and Dana diffs.
A Dana diff from a Jaguar, Volvo, or a Jeep all have gears and internal parts that directly fit and interchange.

Warpspeed,

What ratios are available for the R160 and R180? I could never seem to find anything in the mid to low 3's (i.e.3.50 or lower) for an R160. I have seen some 3.54 or lower for the R180 I believe in a Lexus. that will drop into a 240sx (r180) diff?

Cory,

You are correct about the Saker kit, they are not supporting the rear of the layshaft, in the picture where they show the nut and the two splines you can see the pocket where the bearing goes, they should have made their adapter fit the ID of that bearing, something else would need to be added to keep the bearing in the pocket since it was captured by the center diff previously, but it seems like a horrible idea to leave that shaft end unsupported. I don't think there is any need to support a thrust load since both shafts would have been free to slide in the center diff in the stock configuration. Do you have any reason to believe that FFR is going to use that kit and not make their own?

R160 is difficult, they are a small diff, usually fitted to small cars with small engines, often with overdrive transmissions. So you will look in vain for any really tall ratios.
I believe Subaru use 3.7 and 3.54 rear R160 diffs in some models and that is about it. R34 GTR uses a 3.54 R160 at the front.

The R180 is more common over a wider range of larger vehicles, but again 3.54 and 3.7 are as tall as I have ever seen.

It is why I finally gave up on the Japanese "R" diffs, and went to a Dana 30, which is about the same physical size as an R180, but ratios like 2.75 and 3.08 are available, and many other ratios besides in the range you are interested in.

After a quick trip to the garage and my box of WRX transmission internals I've decided that the layshaft is probably supported well enough without the bearing from the center diff, there really isn't that much shaft hanging out and only one gear on that side of the rear bearing. It would still be a good idea and couldn't hurt to use that extra support, especialy in a known to be weak gearbox, but it's probably not as bad as I thought a few minutes ago.

The front diff is pretty basic, but I kinda doubt it could it be swapped for a standard rear diff. As far as the gearing goes, you can't use anything from a rear diff since the pinion is concentric with the layshaft and about half as long as the transmission. The only gear ratios I know of for the front diffs are 3.90, 4.11, and 4.44. there are a couple other rear diff ratios becasue some cars use 1.1:1 transfer gears for the rear drive.

Edit: just realized the gearing question was related to rear diffs not fronts, but I'll leave the info anyway.

280ZX R180 was available with a 3.36, I used to fit them when I put Holden Red motors into 240Z/K or 260Z's which also happens to be a common Holden ratio for the Red.

Thanks for clearing that up for me. This is what I have run into but I wasn't sure if there was something out there that I was missing.

Nope. It is just a concern to have when building/buying a car that mods the tranny like that. I hope FFR will build a better adapter. I've fragged far too many transmissions to be happy with one that has been made weaker That being said, it is only 5th gear hanging out in the breeze, and it is very close to the bearing so *shrug*.

I often wonder how much of the "subaru trans are weak" thing is the fact that you have people doing clutch drops on a awd. Not many trans can take that sort of impact.

Cheers.
Cory

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Build log: viewtopic.php?t=9291

[quote="C10CoryM"
I've fragged far too many transmissions to be happy with one that has been made weaker

Wow, I feel under-experienced. I've never fragged even one! - That's a trend I would like to continue!

Cory[/quote]

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