Circuit Racing

[xr6_prod]

Nick,

Is it a factory stock box, or has it been "rebuilt" ?

How long does the clutch last ?

Also, how bad is the driveline shunt ?

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The box is 100% origional - never been opened. The only change is Redline lightweight oil (blue).

The clutch has lasted over one season (7 races) however it is due for a replacement. Again 100% stock unmodified. My gear changes in qualifying are very close to flat changes.

Driveline shunts usually come from excessive backlash in the diff and/or slop in drive shaft splines. After a seasons racing the splines on the driveshafts are reasonably well worn but they will last for a while longer yet. The backlash on the diff is considerable - however we are rebuilding LSD's every two meetings and keeping this in check - extra backlash in the diff is not such a bad thing for a race car, as the less the backlash the less the driveline power losses are - however it is a fine balance - with too much backlash you can break teeth on the crown wheel because you are not getting proper depth of engaugement. So suffice to say the driveline shunt would be annoying for road use but there is no concequence when racing (as longs as you keep an eye on the aformentioned driveshafts and backlash).

The other source of noise in the rear end is a loud cracking and metallic clunking, usually most evident on slow turns in the pits. This is the LSD plates themselves moving out of position and binding up when worn. Sometime the diff behaves as if it is a locked diff (for a while) and if you do not attend to it the diff will then go completely open centre and spew all the oil out. We need to rebuild LSD centres every 2 race meetings to prevent the above from happening. However we are permitted to run a full spool and we are giving some consideration to using this rather than the LSD.

The diff used by Ford (as people probably already know) is a Dana M86. Fundamentally this diff is well and trully up to the job. I beleive casting of the housing, crown wheel and pinion are robust for most duties (circuit racing and modified road cars) - however the a dedicated drag car might test it. The LSD is a torque sensing - passive, preloaded type clutch arrangement - which is no where near the mark - it is definitely the weak link in the drive chain, and from the day you first drive the car the LSD is wearing itself out. My guess is that most LSD are getting pretty lazy in as little as 10K-20K of spirited road driving - they are effictively only lasting 300km of race duty. Unfortunately there are not too many options on the market at this stage.