Seeking r34 diff advice

[r34killa]

I would like to mention I've done research on this topic. However, I have struggled to find an answer and am here seeking advice.  

I have an R34 Skyline GT-X (series 1), meaning a stock non-turbo automatic. 2 2-wheel drive IRS (no HICAS), and no viscous lsd option. It has an open diff, from my understanding it is a R200 ABS Open Diff 4.08 ratio 3x2 bolt pattern. I have stock GT axles. The car now has been manual converted and running a forged 25det making around 600hp. The open diff is a nightmare.

 

I want to upgrade the rear diff for sure. I am potentially interested in upgrading the axles as well as I know some of the other diffs can be put into my car if the axles are changed - also not really sure how they hold up with the power my car makes. 

 

What is recommended? 

I saw for sale a "R33 SKYLINE RB25DET 4.0 3x2 BOLT AXLE R200 LSD DIFF HEAD" for 750 NZD - is this a potentially good option? Would this be straight bolt on? 

 

Thanks

 

[robbo_rb180]

You want the 5x1 bolt axels or convert to 350z 6x1 (or 300zx TT 6X1 axels)bolt axels with new flanges welded to stubs from leeson engineering or get a nismo gt pro "gtr" centre or find a gtr factory centre and swap that in to current diff with the new axels. 

 

 

[Kinkstaah]

As it currently stands, you have a S15 rear end.

Keep in mind if you do something fancy like put R34 GTT shafts back there you may need to do something fun with your wheel speed sensors to keep ABS, as the GT has a different ABS setup to the GTT. (it is like the S15).

The simplest way is to put a helical diff in there from a S15. A more sturdy way given what you have is to consider a Nismo diff of appropriate lockage (i.e get the pro with different cams to go between 1 and 2 way).

The final way is to convert to something else, but keep in mind what you'll need to do with wheel speed sensors (i.e you will need to do what S15 people do).

[GTSBoy]

FWIW, the tripod CVs in the 3x2 bolt axles are fine for typical road power levels. Like, probably up to 300rwkW. Maybe more. There's plenty of S chassis cars running that much power on them. They're certainly not as good as the 5 bolt ones, but they're not crap either.

I wouldn't go changing all that stuff for no good reason. There are completely aftermarket driveshafts available that will bolt to both the 3x2 and the 5 bolt stubs, that are much thicker with very good CVs on them. I would be buying those if I trashed what I have now.

[r34killa]

@GTSBoy @Kinkstaah Thanks very much for the replies!! So the car has been tuned @ 480kw on a dynapack dyno. ABS has already been removed from the car, so there won't be an issue there. 

 

So far, I've had no problem with the rear axles. However, I primarily want to upgrade the diff for drifting reasons. Upgrading axles was rather something I was considering due to power reasons as well as if it was worth changing the whole rear setup while doing the diff... 

I'm thinking of going with what @robbo_rb180 said: a 1.5 way GT pro diff with some new axles? What do you guys think? what axles would you recommend 

Otherwise, there's a s15 diff for sale near me for a great price .. would save me a lot of money.. do you think this would do me good for the power the car makes? 

thanks - sorry for being a bit of a noob. 
 

[GTSBoy]

A helical (ie, S15) diff would not be a good choice for drifting. The helicals are a great street diff, but they do have some odd characteristics that make them less suited than a proper clutch diff. If you get one wheel up in the air with a helical, it will act 100% as if it was an open diff and freely spin the airborne wheel. No drive at all. Drifting is rough enough and you're going to hit kerbs often enough that this is a joy killer.

Additionally, helicals are not pure magic. They work by jamming in the internal helical gears into the housing, and they do wear there. All the S15 diffs are approaching 25 years old now and they are all worn. So many of us that have them observe that there can be some delay and apparent slop in the way they engage and take up drive. I've just spent a bunch of money putting mine back into my car and am somewhat wishing that I hadn't. I should have just ponied up, worked out what it would take to get a Quaife into it, plus a new CW&P from Neat.

So, the GT Pro is by far the best option for you.

There is still no need to change to 5 bolt driveshafts. The increase in strength from the tripods you have to the proper CVs is not going to be large enough to justify the effort and expense in finding drivehafts and appropriate stub axles. Although, having said that, I think when you buy a Nismo diff they come with the necessary stubs. But this is complicated because:

• Standard viscous LSDs have one long and one short spline, which doesn't work with the mech diffs, so they have to supply stubs.
• Open diffs have, I think, spline lengths on their stubs that actually work with the mech diffs. So I'm not sure if they do supply stubs with the centre when you buy a centre to upgrade an open diff (as opposed to buying a centre to upgrade a VLSD). Note that the Nismo kits for different diff types all have different part numbers because they know the differences between the various diffs.
• If you buy a Nismo diff for an S-chassis 3x2 VLSD you will get 3x2 stub axless with it, and if you buy for a Skyline chassis you get 5 bolt stub axles.
• So you need to make sure everyone involved understands what you are doing and what bits you are working with before you drop your coupla grand. Otherwise we get a bitch thread next.

Following on from all that - if you need stronger driveshafts, and at that power level you may well need them, because drifting is anything but kind to them - then I'd be looking to buy actual upgrades, as I first mentioned. And they are universal so they will work with either type of stub axle.

Edited September 2, 2024 by GTSBoy

[GTSBoy]

These are the cheaper end of the stronger driveshafts I mentioned. 50% stronger than stock.

https://www.nengun.com/d-max/reinforced-driveshaft?srsltid=AfmBOopNJmSVvKiXvUoqd1iA6Sl6UssD06heku5ytVTGo9lN1gj8h-mG

Also, when I said "Skyline chassis" above, I meant Skylines with VLSDs. Not NA cars with 3x2 stubs.