I took my wife's '95 Disco 1 V8 to the dealer to have a full
transmission service done at a cost of about $370 (190 quid?)
during which they flushed the fluid, replaced the pan gasket, and some
various other O-rings and stuff.

This car has had regular tapping ticking noises from what I THOUGHT
was the top end of the motor and I was researching doing a complete
top-end rebuild, since it has 170,000 miles on it!  I was going to
replace the cam, lifters, pushrods and rocker shaft assemblies along
with the timing chain and all the requisite seals in the area.

Well now the tapping is all but gone!  I can't remember the last time
the engine sounded so good, but the noises are completely gone.  I'm
baffled, because I was positive I was hearing top end engine noises,
but after the trans work, I don't hear a thing!

What the hell could possibly be going on here?  The engine used to
tick in every gear selection including P and .

While I'm certainly not complaing about the fact that the engine
suddenly sounds great, I'm very confused.  I seriuosly doubt it's just
a coincidence, since the car has faithfully tapped/ticked for years
now, no matter what oil it has in it.