User:Fergie4000/Sandbox

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What diffs came in the R31?
The R31 Skyline and Pintara came with 2 types of BW78 (also known to some as BW75) diff center. The Skyline had a 28-spline, 4-pinion center. The Pintara had a 25-spline, 2-pinion center.

The skyline center is naturally therefore stronger than the pintara center.

2 pinion diff

4 pinion diff

What diff ratios are available?
The Skyline came from the factory with these 2 ratios depending on whether the car was manual or automatic.
 * Manual = 3.70
 * Automatic = 3.89

The only exception to this rule was the GTS2, which had a 3.89 ratio regardless of transmission type.

The Pintara came with a single ratio of 4.11 regardless of transmission type.

A wide variety of ratios were available for the BW78 diff. These include:
 * 2.73 (Ford Falcon)
 * 2.90 (Ford Falcon)
 * 3.08 (Ford Falcon, Holden Commodore)
 * 3.23 (Ford Falcon, Holden Commodore)
 * 3.42 (Mitsubishi Sigma)
 * 3.45 (Ford Falcon, Holden Commodore)
 * 3.70 (Mitsubishi Sigma/Nissan Skyline R31 manual)
 * 3.89 (Mitsubishi Sigma/Nissan Skyline R31 automatic)
 * 4.11 (Nissan Pintara)

What diff centers will fit in the R31 housing?
During its reign the BW78 diff was a very popular diff, being used in almost all locally produced family vehicles.

Examples include:
 * Ford Falcon - XD to AU (6 cyl or V8)
 * Holden Commodore - VL to VT (6 cyl, V6 or V8)
 * Chrysler Valiant - Late models
 * Mitsubishi Sigma (2.0 or 2.6)

All of the above mentioned centers will fit inside the R31 housing. Longevity requires correct adjustments made to the new center. IRS versions of the commodore center are also interchangeable.

What L.S.D centers are available?
The R31 came with the optional BW78 Cone type L.S.D: 28 spline, 4 pinion.

This diff is a very effective diff for providing Limited slip in slippery conditions, however the design does not lend itself to durability. Many users experience a loss in the locking ability of this center between 3 months and 1 year of regular hard usage. These centers can be rebuilt (reshimmed) but will have a similar lifespan.

Most L.S.D centers that you will find out of other BW78 cars will be based on this design.

They are available in the following configurations: 25 spline, 2 pinion (Ford Falcon - XD, XE, XF. Holden Commodore - VL) 28 spine, 4 pinion (Ford Falcon. Holden Commodore - VL turbo, VL V8, VN onwards)

KAAZ diff centers are available for the BW78, and is quite possibly the best aftermarket L.S.D available. They are a much better design, based on clutch packs, rather than cones.

The most available KAAZ center is what is know as a 2 way diff, which applies lock under both acceleration and deceleration.

Available in 28 spline, 4 pinion

Eaton does a Torsen based center for the BW78, it is a very sturdy design. Its based on another set of gears inside the center, which under slip, adds torque to the wheel that has more grip, based on a multiplication factor.

Other locker options
If you feel the need for some locker action, you have three main options.

Minispool, which is a locking device that replaces the spider gears in the center with a solid metal cylinder. Hard locks the two axles together.

Welded Center, which is what it says, a center that has had the spider gears welded to the centers housing. Hard locks the two axles together, durability is questionable as opposed to the minispool as it depends on the quality of the welding.

Fullspool, which is the big brother to the minispool, it replaces the diff center with a solid carrier that only holds the crown gear and has two sides for the axles to enter, will hold stupid power levels. Hard locks the two axles together. Used by V8 Super Cars.

Contributors: Session, Mainyard

Ratings
When choosing oils the better the rating, generally the better the oil, and also the more expensive. Keep in mind even the Group II oils are probably still better then any oil that was made when your car was manufactured.

Examples
Common products and their ratings (some may not be 100% accurate and may be blends between certain ratings).

Viscosity
The viscosity of the oil is one of the most important factors when deciding which oil to use. Newer engines use thinner oils because they have much smaller tolerances than older higher mileage engines. As rings, bearings, lifters etc wear these tolerances become larger, and a thicker oil can be used to take up the gap and reduce wear that would be caused if a thinner oil was used.

Grades
For an oil to be classed as say a 5W oil, it needs to be able to flow a certain amount at a low temperature. This first number is the oil's "cold" viscosity. The standards for measuring oil viscosity are determined by the SAE (Society of Automotive Engineers) and all engine oils use the SAE's standards for measuring viscosity.

The "W" suffix simply means that the oil is suitable for use during winter, meaning the oil will not become too thick under the lower overnight temperatures (usually only oils with a cold viscosity of 20 or lower will be classed for winter use, although I have seen a few 25W oils)

The second number is the oil's "hot" viscosity. This is a little harder to explain. Multigrade oils contain polymers which react under heat, and actually expand as they become hot. This is what prevents multigrade oils from becoming too thin under hot conditions. That's all well and good, but what does this second number have to do with that?

If you were to warm a monograde 40 weight oil to 100°C (210°F), it would be thinner than a 15 weight oil at cool temperature.

So, if you were to test a 15W-40 engine oil, it would have the viscosity of a monograde 15 weight oil at it's low temperature, and when warmed up it would have the viscosity of a monograde 40 weight oil at high temperature.

Filter Upgrade
The Ryco Z115 may be used as an upgrade from the normal Z145A on some engines due to it's larger size. The larger size of the filter increases oil capacity to almost exactly 5L. It may not fit on all engines due to its larger seal diameter (70mm as opposed to 63mm on the Z145A). Ensure that the seal seats properly if this filter is used to prevent oil from spewing everywhere. An oil filter sandwich plate may be used to get a bigger contact area to allow the filter to seal adequately.

Genuine Comparison
They both look the same externally. The Ryco was $7.70 from Burson, the Nissan $12 from Nissan. They don't come out of the same factory, Ryco from South Africa, Nissan from Thailand. Looking down the barrel of a used Ryco: Looking down the barrel of a new Ryco, they've changed the design since last time, I don't know if the one I'm gutting came from South Africa or not, the old one looks the same as a Nissan inside, but the new one has a spiral design: And the used Nissan, the different colour of the anti-drainback valve is visible. Nissan guts left, Ryco guts right. Nissan is taller and bigger diameter, point to Nissan. The Nissan anti-drainback valve appears made out of silicone rubber or something a bit exotic, Ryco valve made of plain rubber and bigger, doubt it matters much either way. Springs for bypass function visible either side. The Nissan spring is easily compressible. The Ryco spring is almost impossible to compress. So the Nissan would bypass a blocked filter element or sludgy oil much more easily than the Ryco. I would hope that my filter never got to that stage. Point to Nissan? Don't know. The internal diameter of the Nissan filter element is smaller than the Ryco, point to Nissan again. Although the Ryco has more holes. The Nissan filter is about 2200mm long and exactly 65mm wide - 143 000mm2. The Ryco filter is about 1900mm long and exactly 60mm wide - 114 000mm2. So Nissan filter has about 25% more area, point to Nissan. I clearly have no way of testing the efficiency or flow rate of the filter paper: They are not identical internally, and the Nissan does look a bit better.