In reply to a message from tomsprechs@yahoo.com sent Tue 11 Feb 2003:
Jerry,
On an XJ40, there is not a torque figure specified for the pinion
nut itself in the Tech Specs. The pinion bearing pre-load is set
using the crush tube method by measuring the BACKLASH torque ( i.e.
the torque required to take up the play between the crown wheel and
pinion) and that is measured only in lb/INCHES (Spec = 35 - 55
lb/inch).
It’s a ‘one-shot’ type excercise because if you tighten the pinion
nut a fraction too far and exceed the backlash torque specification
the crush tube is knackered and you have to start all over with a
new crush tube.
On my car, the pinion nut itself was so tight, I could not undo
it with a long breaker-bar when I tried to replace the pinion shaft
seal. I had to take the car to a shop and have them remove it with
an air impact wrench. No doubt that was due in some part to the
application of ‘thread lock’ during initial build, but if that is
the case with other XJ40 pinion nuts, you really have no chance
of ‘tightening it up a bit more’ as you suggest without a serious
risk of overdoing it, exceeding the backlash torque, ruining the
crush tube and if left in that state, the pinion bearing itself.
As Brett has mentioned, he found out that messing with the pinion
nut is at best a temporary relief and IMHO it potentially will do
more harm than good.–
The original message included these comments:
Read the bit you said about whine on overrun- check the pinion
nut torque, and find the spec for what pinion bearing preload is
supposed to be-if it has loosened up even slightly, maybe you can
get some silence by tightening the nut up a bit more, not to exceed
spec from Tech Data.
–
Bryan N ('91 Sovereign)
Cambridge, United Kingdom
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
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