Listen for noisy or slow starter,knockin or rattling from gearbox at idle & vibration from gearlever when revved.
All signs the flywheel (DMF) is on its way out.....££££££.Tend to knock more when warm & as you turn engine off.
Roadtest & listen for diff & wheelbearing noises,bearing noise will alter when steering turned.Diffs usually alter on & off the throttle.
Other favourites include; More than 3 things tho i`m afraid

(if only

)
oil leaks=brake vac pump, front & rear crank seals.
check in coolant reservoir for signs of engine oil=cooler bust
play in viscous/cooling fan hub
Fan belt tensioner bearing failing
A jarvis favourite,propshaft rear u/j collapsing
front tyre wear,usually inner edges.
Play in steering rack & track rod ends.
Lower arm rear bushes splitting
Roadtest to see how it pulls,keep an eye on glowplug light.
Timing chain rattles.
I have serviced vans for jarvis/network rail & although they do have regular services/repairs at main dealers,
The people that drive them don`t tend to look after them very well,there just workhorses (no offence to any of said people

)
Theres other stuff goes wrong,but its stuff u can`t really check & won`t see coming
