The Differential Thread

[Kgolf31]

So, I'm starting to look at the differential differential options to eventually purchase one and install in my car this upcoming spring for my STX Build.

As it stands, here are my available options.

Torsen Based
Clutch Based w/Set 45/45 Ramps
Clutch Based w/Custom Ramps
OS Giken

I'm trying to evaluate what would be the best application for me. The car will be seeing less and less miles as the year goes on. So as far as noise, I'm not concerned.

Torsen would be ideal because of 0 lockup when off throttle. This will help with turn in and there really is no extra service needed.

Clutch, depending on ramp angles could create more push off-throttle. However depending on the ramp on-throttle lockup can be very precise and probably better over a torsen. We also have static lock here.

OS Giken is probably the diff to get. However it is picky on the fluid it sees, as well as the 20 some clutch plates there is obviously going to be some extra service involved here.


Also, I can go with 2 different install options:

Chunk
Pumpkin + Chunk


Anyone have some thoughts or experience to chime in here? I want this to kind of be educational so people can relate back and see who chose what and why.

[3002 tii]

While at it you should think about possibly change to a gearing better suited for auto-x which never leaves 3rd gear (disclaimer: no clue if your current gearing works for you or not, just throwing out there).

If you don't mind the cost and maintenance I don't think anyone can argue against OSG. Clutch type is good but you should really speak to a diff specialist or a fellow auto-xer familiar with the 1 to make recommendations on rates. I have a a Torsen based and it's served me well but I know it's not the ideal solution for a road course.

You're close to Brett @ KMS, I would have him do the install considering his rates are more than fair and he's as good as they get. Then you can just do the pumpkin swap yourself.

[TheSt|G]

OSG is pretty well disliked in the 911 world. The general consensus is that they are a massively overpriced clutch diff that doesn't live up to the name hype.

Torsen is definitely a street focused diff. I love them but it seems poorly matched to your application?

Don't forget to get the BMW/Quaife finned diff cover when you do this.

[Kgolf31]

Originally Posted by 3002 tii

While at it you should think about possibly change to a gearing better suited for auto-x which never leaves 3rd gear (disclaimer: no clue if your current gearing works for you or not, just throwing out there).

If you don't mind the cost and maintenance I don't think anyone can argue against OSG. Clutch type is good but you should really speak to a diff specialist or a fellow auto-xer familiar with the 1 to make recommendations on rates. I have a a Torsen based and it's served me well but I know it's not the ideal solution for a road course.

You're close to Brett @ KMS, I would have him do the install considering his rates are more than fair and he's as good as they get. Then you can just do the pumpkin swap yourself.

Unfortunately I need to stick to the stock ratios for STX (3.23 in my case).

With the increased limiter I'm at 66-67 MPH at second gear...which is pretty good.

I want to check with KMS to see what they can provide. Also considered getting a diffsonline unit and doing a direct swap.

Originally Posted by TheSt|G

OSG is pretty well disliked in the 911 world. The general consensus is that they are a massively overpriced clutch diff that doesn't live up to the name hype.

Torsen is definitely a street focused diff. I love them but it seems poorly matched to your application?

Don't forget to get the BMW/Quaife finned diff cover when you do this.

I don't know if I can actually do a finned cover for the diff. I need to check with that.

And just for another data point. The FRS/BRZ stock comes with a torsen diff. The national champion, Andrew Pallotta who drove a FRS won on a stock diff.

[andrey_gta]

Originally Posted by Kgolf31

I don't know if I can actually do a finned cover for the diff. I need to check with that.

And just for another data point. The FRS/BRZ stock comes with a torsen diff. The national champion, Andrew Pallotta who drove a FRS won on a stock diff.

The e60 2004 530i/525i AT has a finned diff cover that fits our 188mm pumpkin. I strongly believe its the Quaife cover Stig mentioned.

Torsen style has some cheap options - the Mfactory brand recently did a bunch of group buys and I believe the reviews here and bimmmerboost/n54boost are positive. They even have begun to cater to the n54 welded diff people, which is very nice of them. They even have Clutch diffs too.

[dcaron9999]

Some hard core lappers prefer clutch based LSD's, and recommended I go with this option.

I think the M cars are clutch based "variable lock" LSD's. The m variable unit gets clunky after continued abusive driving. This is why so many were replaced under warranty.

After some research, decided to go with a Quaife (torsen) earlier this year. I wanted a low-cost, low maintenance (no clutch plates to replace), no specialty oil, and a brand with a solid reputation.

I found a used large pumpkin/bolted diff at a recycler, and got the 3.08FD "chunk" converted to a Quaife 3.46FD.

The torsens are probably not the best out there, but for a dual duty car, Im quite happy with the results. it really transformed how power is appllied to the ground. It removed snap oversteer, and made the car predictable at turn out. It is very noticeable even on the street, during hard accelerations, and low grip conditions. The car steers straight now, but rear-end used to twist and DSC would frequently intervene with the previous open "e-diff" ...

[TheSt|G]

Originally Posted by Kgolf31

And just for another data point. The FRS/BRZ stock comes with a torsen diff. The national champion, Andrew Pallotta who drove a FRS won on a stock diff.

Don't get me wrong, I think they are wonderful(I have a Quaife in the closet I need to get around to installing). But there is a reason they aren't found on top spec performance cars.

[chris82]

Also, my vote goes to Quaife LSD. Be sure to get the VAC finned diff cover

Don't want to get off toppic, but the 128i has a 3.23 diff and the 135i has a 3.08?

[andrey_gta]

Aside from this Part of me think one can use the 2 Series M Sport/M perfromance units
it would be like using a 135i diff- changing the half shafts etc... Unless they make it for the 228i which still should have the 188mm pumpkin

yes the 128i has 3.23 MT 3.73AT
the 135i has lesser final gears, obviously a different transmission gearing too so net effect is still probably in 135i favour

[TheSt|G]

Originally Posted by andrey_gta

Aside from this Part of me think one can use the 2 Series M Sport/M perfromance units
it would be like using a 135i diff- changing the half shafts etc... Unless they make it for the 228i which still should have the 188mm pumpkin

You probably can, but that is a half assed diff designed to be worse than the M units and costs a ton. No thanks.

[andrey_gta]

Lol. I guess, makes sense that its not very dedicated diff

[TheSt|G]

Originally Posted by andrey_gta

Lol. I guess, makes sense that its not very dedicated diff

I think it has somewhere in the neighborhood of 15%-20% lockup?

[Kgolf31]

Originally Posted by TheSt|G

I think it has somewhere in the neighborhood of 15%-20% lockup?

Yea, it isn't anything to die for.

[631twentyeighteye]

I imagine that for your use you want the clutch type. Personally i plan on going with wavetrac, mfactory, or quaife. I've only began researching each option but they're all gear driven so its essentially the same thing.

Are you planning on changing all the associated bushings when you're in there? I plan on doing LSD, diff bushings and the subframe bushings while i have it apart. I'm inclined to say i'll be starting this next summer.

[Kgolf31]

Originally Posted by 631twentyeighteye

I imagine that for your use you want the clutch type. Personally i plan on going with wavetrac, mfactory, or quaife. I've only began researching each option but they're all gear driven so its essentially the same thing.

Are you planning on changing all the associated bushings when you're in there? I plan on doing LSD, diff bushings and the subframe bushings while i have it apart. I'm inclined to say i'll be starting this next summer.

I'll do diff bushings. I already have subframe bushings done since I'm running #700 lb springs in the rear

[Taskmaster]

Originally Posted by TheSt|G

Don't get me wrong, I think they are wonderful(I have a Quaife in the closet I need to get around to installing). But there is a reason they aren't found on top spec performance cars.

I thought 911's come with a Torsen unit?

OP have you considered Wavetrac? Aren't they a combination of Torsen and clutch style diffs?

[631twentyeighteye]

I see. I forgot you're mostly prepped already. I'm undecided if i want to change to a higher final drive or not. I think it'd be beneficial but it mostly depends on highway drivability.

[TheSt|G]

Originally Posted by TheAxiom

I thought 911's come with a Torsen unit?

OP have you considered Wavetrac? Aren't they a combination of Torsen and clutch style diffs?

911s come with the shittiest clutch diffs in the world. One good track blows out most of them, including the units on the GT3. Seriously the cheapest part of the car. Most serious owners upgrade to a Guard unit.

[_Ryan_]

I have a Quaife in my 130i, it's a nice traction aid for a street car.
Note: I live on a mountain, frequent 100km/h (62mph) winding roads both sealed and unsealed. Low maintenance was also a factor in this decision.

In the past I have owned a Cusco 2way clutch LSD in a RWD JDM car, for a weekender and track car, a clutch 1.5way LSD would be my preference.

If you would consider a 1way clutch LSD, get a Torsen and save money.
Else, if you would make use of a real diff and/or can hold a slide and/or can deal with the service costs/time, buy a 1.5way.

Speak to Jesse Streeter, an Australian living in Japan who is pretty good with sourcing parts.
He did the research with me, the OSG part number for the BMWs isn't on par with the JDM equiv- apparently made and sold under licence. A KAAZ is cheap and reliable for a track hack, a Drexler is arguably superior but will cost 250% !

[chris82]

Originally Posted by 631twentyeighteye

I see. I forgot you're mostly prepped already. I'm undecided if i want to change to a higher final drive or not. I think it'd be beneficial but it mostly depends on highway drivability.

Yea, the most I would do is a 3.46. That's about a 7% increase. I don't know what I'm talking about but wouldn't that increase your RPMs at a given speed by 7% too?

[andrey_gta]

Originally Posted by Chrisar82

Yea, the most I would do is a 3.46. That's about a 7% increase. I don't know what I'm talking about but wouldn't that increase your RPMs at a given speed by 7% too?

Going up decreases the top speed of each gear, so yes probaly 7% increase in RPM for a given speed, but acceleration is better.
@justpete swapped in a 3.73, I wish he would comment on the new shift points and daily life. That is a 15% increase and its very tempting because of numerous junker 3.73 parts for sub $500

For a 128i to get 3.36 or 3.46 we have to either get a custom small pumpkin or think about drive shaft mating to large one and half shaft fitments. I have no idea what is a direct swap

[chris82]

Originally Posted by andrey_gta

Going up decreases the top speed of each gear, so yes probaly 7% increase in RPM for a given speed, but acceleration is better.
@justpete swapped in a 3.73, I wish he would comment on the new shift points and daily life. That is a 15% increase and its very tempting because of numerous junker 3.73 parts for sub $500

For a 128i to get 3.36 or 3.46 we have to either get a custom small pumpkin or think about drive shaft mating to large one and half shaft fitments. I have no idea what is a direct swap

I'm not sure I follow. Why is the 3.73 easy to find and the 3.36/46 is needing a custom small pumkin?