2 way diff and ratio's answered

[Arnie]

Hi,

I thought I'll contribute to the forum and put some info that I couldn't find definite answer myself.

For those wondering whether to go with viscous diff, 2 way or welded there's my thoughts (from own experience, not internet bullshit):

1. Viscous diff - if fresh, tight (you can barely spin the knuckles in opposite directions by hand) it will do on the street, getting out of roundabouts etc very well. It can be tightened by adding shims (google it). I never had a problem with it, didn't find it unreliable or getting loose, it's just slower in reaction (delay, bit lazy) compared to a 2 way.

Not sure on the diff oil - someone elaborate

2. Proper 2 way - I installed a Tomei one yesterday and car feels much tighter (less daily traffic friendly), car doesn't want to turn at low speeds (understeers a bit) but things change if you drive hard and transfer weight, then it's the job. There's no wheel hop when turning though and locks immediately, much faster than viscous one. I didn't find it dangerous when breaking (maybe I'm used to this kinda driving) if proper driving technique is applied.
It requires proper diff oil with friction modifiers - BOA 90 from Silkolene (now Fuchs oils), about 1.5l (I spilled some so don't know exactly)

3. Welded diff - I drove a car with a welded one, was a headache to manouver when engine broke, always locked, car lazy to turn in at low speed. Was fun on the track but I can't see it long term as the welds will eventually come loose and this can kill you if it happens on the street (lock the back end completely)

4. S15 helical diff - someone elaborate


The exact ratio of the diff can be found by opening up the case (rear cover). There's numbers stamped on the gear in a xx:yy format, divide those numbers and that'll give you the ratio.


Changing the diff is a 2 hrs job (including jacking up the car etc) but in my case it turned out to be a 10 hrs job because some idiot damaged threads in the subframe and put bolts and nuts instead (cut subframe on the top). I had to pull the whole subframe out and put it back (that's all on my driveway in the rain) so beware of it. I also opened up the diff for inspection, put new seal on and new gear oil.


I'll put up pics when I buy a new camera.

Hope this helps someone.

[skinnynphats200]

4. S15 helical diff - someone elaborate

[/QUOTE]

Yes would like to know this - same in my rx and still looking for info on it

[flynhy]

Yes an answer for s15 diff will be helpful..

[PeterT]

Welds cant 'come loose' if welded properly. Infact a welder will put up with more abuse than a 2 way if done right!

[Stevo]

Welds cant 'come loose' if welded properly. Infact a welder will put up with more abuse than a 2 way if done right!

Yup once welded right should last forever unless ur a rough huar

[Arnie]

Ok, thanks guys for the input.

I haven't driven a car with s15 helical (Torsen type) diff but I was told (by EoinR) that it's unpredictable and crap for going sideways (he almost crashed one car with it and we all know his mega skilzzzz). Quick search on google reveals that:

"The only thing i don't like about the helical is if you lift the wheel up or take the weight off the wheel it spins like a open diff. very annoying on the track".

"The Helical diff is crap for drifting for exactly the same reason its fantastic for road and track."

From Wikipedia:

"The S15 differential has gears that are cut in a fashion that when the car is turning the gears mesh together and transfer power to the tire with more traction. It does not lock like a clutch diff, but is very smooth. The best thing about a helical diff is that it practically never wears out. You can treat it the same as an open diff: change the oil regularly and it will likely outlast the car.
The S15 helical differential is probably the best diff for road racing applications. It is not recomended for drifting because it never actually locks. The differential can only multiply the torque it can apply at the side with low traction, so if one tire has very little traction (such as on ice or in the air) then the differential will act the same as an open differential."