2 way diff and ratio's answered

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:confused:) 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.

4. S15 helical diff - someone elaborate

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

Yes an answer for s15 diff will be helpful..

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

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Originally Posted by PeterT

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

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

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."

Ok I definitely need to take out my diff so if the above is the case. I'm not sure if it has an aftermarket diff or the torsen type standard but from what I can see the half shafts are not standard I don't think; the half shaft housing coming from the diff are a bright green colour and don't look to have been sprayed either and I dont think this is standard. All I know from trying to slide is that it grabs traction really quick, im constantly fighting with it to try and stop it straightening out once I initiate.

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Originally Posted by skinnynphats200

Ok I definitely need to take out my diff so if the above is the case. I'm not sure if it has an aftermarket diff or the torsen type standard but from what I can see the half shafts are not standard I don't think; the half shaft housing coming from the diff are a bright green colour and don't look to have been sprayed either and I dont think this is standard. All I know from trying to slide is that it grabs traction really quick, im constantly fighting with it to try and stop it straightening out once I initiate.

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jack up the car so both wheels are off the ground and spin one wheel, if the other spins the same way you have a proper 1.5 or 2 way if i recall. if one spins the other way its a helical

Alright cool, cheers

Lift both rear wheels and turn one wheel, if the other one moves in same direction it's a 2-way, 1.5 way or viscous diff. If the other wheel moves in opposite direction it'll be an open diff.

Not sure on helical one ie the way it spins.

If someone has any comments please post but please stick to facts and own experience as internet is full of bullshit.

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Originally Posted by Arnie

Lift both rear wheels and turn one wheel, if the other one moves in same direction it's a 2-way, 1.5 way or viscous diff. If the other wheel moves in opposite direction it'll be an open diff.

Not sure on helical one ie the way it spins.

If someone has any comments please post but please stick to facts and own experience as internet is full of bullshit.

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Ok both wheels spin the same way, but I was told that all this indicates is that I have some sort of an lsd, but does not indicate a 1.5 way or 2 way?
I would like to know is there any other way of telling what diff it is without taking it out and opening it up

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Originally Posted by skinnynphats200

Ok both wheels spin the same way, but I was told that all this indicates is that I have some sort of an lsd, but does not indicate a 1.5 way or 2 way?
I would like to know is there any other way of telling what diff it is without taking it out and opening it up

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my s15 when jacked up one wheel goes one way the other the opposite direction and thats got a helical diff.... they lock using torque rather than clutch plates...id say you have a proper locker in it imo anyway :D

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Originally Posted by stevek

my s15 when jacked up one wheel goes one way the other the opposite direction and thats got a helical diff.... they lock using torque rather than clutch plates...id say you have a proper locker in it imo anyway :D

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Is your helical an LSD though? Yeah afaik mine is a Torsen torque sensing LSD - it apparently locks both wheels, but only when either one of the wheels exceeds 75% of the load....i.e if one wheel has 60% load and the other has 40% the wheel with only 40% will spin and the other won't.....its not a 50:50 ratio if ya know what I mean

Im fairly clueless when it comes to diff's so bear with me on this one lol. When i bought the s14 the lad gave me a spare diff and said it was a 2way.Never got around to fitting it because i dont know what it really is. When i turn the flange where the prop shaft bolts to the diff turns the same way either side.I also opened up the cover and there is a 4 and an 8 painted on the big gear....is this the ratio? Like i said im fairly clueless so any help would be much appreciated.

just out of interest my diff is a 2way and when turning at low speeds or reversing and turning i get loads of tyre skiping and klunking sound, but driving normally at speed its sound and wud kill ya in the wet is this normal?

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Originally Posted by AndysR20det

just out of interest my diff is a 2way and when turning at low speeds or reversing and turning i get loads of tyre skiping and klunking sound, but driving normally at speed its sound and wud kill ya in the wet is this normal?

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That's normal for a lot of 2ways diffs :cool:

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Originally Posted by Cooldrft

That's normal for a lot of 2ways diffs :cool:

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OR its a sign that you have a welded one there (someone lied to you when you bought the car etc), proper 2 way should have that very little bit of "go" in it (at least mine does).

So whats the DIFFerence:D between a 1.5 and a 2way diff?
Is there just less give in a 2way?

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Originally Posted by C_O_N_O_R_

So whats the DIFFerence:D between a 1.5 and a 2way diff?
Is there just less give in a 2way?

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A 1.5way will be that bit better if you were using on the road. It doesn't lock both wheels on deceleration, only only acceleration whereas a 2 way will lock them up constantly

Edit: Oh, I see what you did there, I see it, its good

think there was a helical diff in my s15 when i first got it, it was grand in the wet but shit in dry. As soon as i swapped it out for a proper 2 way the difference was amazing though so i then realised how shit the helical s15 diff was!!