40 replies to this topic

[rodomo]

Q.Fine and coarse spline axles, whats the diff?
A.The diff is the bit between the axles regardless of coarse or fine splines.

[dattoman]

Course spline Holden is about 10 splines
Fine has more but I can't remember how many ... haen't broken any in awhile (28 maybe ?)

So thats the easy method..... course or fine

The more splines the stronger the axle
Talking Ford 9" they start at 28 and you can buy axles and centres in 31,33,35 and beyond

[Peterpilot]

What are the advantages/disadvantages of either a coarse or fine spline axles in diffs?

Coarse spline: I've broken plenty of these, they snap like celery sticks.
Fine spline: I haven't broken any... yet.

[Heath]

Course Spline are 10 splines, Fine Spline is like 18 or something isn't it?

Anyway the fine spline axles distribute the torque more evenly around the axle to compensate for its tiny diameter. I've been led to believe that they make a significant difference in strength.

[rodomo]

More input:
Coarse are cut further into the axle thus making the machined diameter of the axle smaller therefore weaker.

Edited by rodomo, 02 August 2007 - 12:36 AM.

[WhiteA9XS]

greg you forgot the salsbury

[Struggler]

V8 Salisbury is 28 spline, identical to pass. 9" in diameter, pitch etc.

[enderwigginau]

Have a look at the UC disc brake conversion article for pics of Torana coarse and fine spline axles.

Please note that the die/mould for torana axles changed with the UC, so UC axles should be a much solider unit compared to an identically splined LH/X unit.

Grant..

[mr5000]

dont think so ive got a kingsy centre in the garae and its bigger than a banjo

[76lxhatch]

I have heard that you can use a kingy fine spline diff centre (HQ for instance) and UC axles in an LX/LH diff housing and get a stronger diff. Any one done this or know if it will work?

Almost - the later model (e.g. HZ) six cylinders had the fine spline Banjo centre (utes had LSDs too), which will fit into any Banjo housing. Then add UC axles which have the fine spline and you are away. You can also just rob the fine spline side gears from the UC Salisbury and put them in the Banjo centre.

[Heath]

Sure is an old thread ya found!

Some standard ones may be cold formed (particularly the V-type splines found on fine spline Torana diffs as opposed to the squaretooth splines found on coarse spline Torana diffs), I've only ever seen them machined but I haven't worked in a factory that mass-produces them.

One of the problems with the typical production car splined arrangement is that the outer diameter of the splined area is the same as the shaft diameter. This means that you get effectively a smaller diameter axle under where the splines are situated. So you're using excessive material for the same torsional rigidity if that makes sense. Basically you end up with a spline diameter that is undersized and a shaft diameter that is nominally oversized (or both undersized in the case of a Torana LOL) and isn't giving you any strength anyway because that isn't the weakest point

The best way to do a splined shaft is to have a larger diameter at either end of the shaft, with a radius leading into that diameter so that there are no stress concentrations (another problem with the typical production car spline arrangement). If the smaller diameter matches the depth of the splines, then you just machine the splines into that larger diameter, back and forth with an indexing head of some description, until you reach the nominal shaft diameter. This also means that the axle is allowed to 'wind up' a little bit so that the peak destructive forces are spread out over a matter of a very small timeframe which seems to make a difference, and when you have a shaft of this design it ends up being lighter too, which in a diff is bloody important if you actually want to go around corners and get the car to handle as well as possible.

Edited by Heath, 02 June 2010 - 11:57 PM.