Shimmming Up The Viscous Diff Project Underway.

[CEF11E]

I have been stuck at home with a nasty case of sushi poisoning and have not been able to replace the diff myself so i have sent the shimmed centre along with the car to the good blokes at the diff place and will be picking it up finished on friday. an will be taking the car drifting on sunday so will be able to give good idea of how it works.

Cheers!

[skylinegtts]

I have been stuck at home with a nasty case of sushi poisoning and have not been able to replace the diff myself so i have sent the shimmed centre along with the car to the good blokes at the diff place and will be picking it up finished on friday. an will be taking the car drifting on sunday so will be able to give good idea of how it works.

Cheers!

ahh man that sucks.

how much did u pay if u dont mind me asking? just getting an idea for wen i go to get it done so i know around about figure.

cheers

[CEF11E]

All in and done.

I paid $100 for the centre $22 for the shims and $200 to swap the centre over

if you already had an LSD you would only have to pay about $222!

or risk doing it yourself.

I haven't had a chance to really try it yet. I gave it a bit of stick on the way home but not enough to feel it. it drives like factory but feels like it does not under steer as much around corners.

the track on sunday will be the test.

[MANWHORE]

Sushi is seriously nasty shit. These days, I see heaps of people eating it because they think it's healthy and good for them. When I tell them otherwise, they laugh at me.

Sushi:

contains a lot of msg

is usually not fresh and sitting there for god knows how long

Already has a decent amount of bacteria in it when it's fresh because of the ingredients

Anyways, back to your diff, it's awesome that you've had a go at it yourself. Now i'll know who to ask when I do mine

[CEF11E]

A few observations I have made so far.

A R200 Viscous diff operates on the principal of fluid viscosity. the viscous centre is about 2" wide and contains thick fluid and 6 rotating plates with holes. There are holes with splines for each driveshaft. the plates inside the coupling rotate at the same rate as the driveshafts L and R. as one shaft spins faster than the other the viscous fluid creates a viscous bond between the plates and applies rotational force to the other shaft thus providing an LSD effect. The key here being LIMITED slip not non slip. There is a finite amount it will slip and a finite amount it is able to slip.

Adding shims to the diff either on the viscous side or the carrier gear side will not make the total locking effect any greater than what the diff was designed to provide.

All you will achieve is adding more preload.

The preload serves 2 functions.

1. Provide the right amount or lateral movement to prevent excessive wear on gear teeth in the lsd assembly. Too much will cause to gears to bind and not rotate properly and too little will result in a noisy and short life for your diff.

2. Assist in providing frictional load the the assembly and help prevent backlash between the pinion and crown wheel.

So adding thrust washers does the following.

Increasing tension in the LSD centre by increasing preload by squishing the carrier, spider gears viscous coupling together. This will mean as there is more friction the assembly will rotate with less ease and lock both splines together until the preload is exceeded at which time the diff will open wheel for a split second until the viscous centre starts to limit the rate of slip

What does this all mean?

Yes adding washers in your diff will make it tighter until the preload is exceeded by force and then your shimmed diff will provide no more or less slip that a standard VLSD. In practice you will not feel the time between preload slip and viscous take-up it will just feel like mechanical LSD

You will shorten the life of the LSD assembly, crown wheel and pinion and produce more heat as the friction is energy and energy is transferred into heat.

So YES IT WORKS but will in the long term wear out your VLSD. I would guess you are looking at a lifespan of 30~40,000kms

[CEF11E]

I can now confirm that the car will leave 2 nice black marks that are both full and even when i drop the clutch. so the extra preload seems to have helped.

the car is also more predictable around a corner and you can put down more power and that means more acceleration. and when it does begin to slide it is more predictable and a lot more fun.

normal driving is fine. no clunk or shudder.

A good cheap mod and if done correctly you will gain a lot

[Cubes]

Excellent.. So you ended up using the 2 x 1.01mm shims?

[CEF11E]

yep 2 x 1.01mm shims. the LSD is now really good it is predictable and held up to 2 solid hours of drifting. it actually feels like a mechanical 1 way as it only locks on throttle. it locks on almost nothing only need about 10 ot 20% before it spind both wheels nicely.

If I was going to do it again i would use 1 x 1.01 and 1 x 1.3mm

[yogi000]

hey ceffie nice work

did you take the original shim out and add 2 new ones?

[CEF11E]

Hi yogi000.

If you pull the centre apart you will find there are actually 2 shims. 1 either side of the assembly. I replaced both of them with 1.01 shims. the ones in my lsd were 0.74 and 0.71 and I am imagining they were bout 0.80 from factory. so they had both worn a bit.

I have a pair of 1.01 shims left over if anyone wants them for $20

[yogi000]

ceffie i'll take em.....pm me your details......i'm gonna give this a shot.

[Eug]

If I was going to do it again i would use 1 x 1.01 and 1 x 1.3mm

any reason for this? does your drift track favor turning one way over the other? (i.e more left turns than right)

or am i missing the point completely?

[CEF11E]

The total load is only relevant to the sum of both shims. it dosen't matter if you use 1 bigger than the other it will lock the same left and right.

so removing 1 1.01mm shim and adding a 1.3mm wil just give more preload to both sides

Cheers

[Eug]

how has this held up CEF11E??? still going strong?

[Cubes]

I ended up shimming my diff.

I found corner exit/acceleration was excellent, always twin wheeled.

However.. Straight line acceleration still saw the diff spinning up a single wheel. Roll on the throttle in first and the left wheel would buzz up. In second when the diff was cold the left wheel would again buzz up.

But for drift etc its definitely a cheap worth while mod that works. Twin wheels predictably all the time.

The diff stopped clunking on sharp low speed turns after about 500km's.

[CEF11E]

mine is starting to get a bit looser again under tight turns on very grippy surfaces.

going a 2way when i can be bothered pulling out the diff again.