Well bad expensive - Saint will be along shortly to give you a run down on what to expect. Lets kick things off with gearbox / torque convertor...
Off out in 5 minutes...so can't stop too long so I'll give a brief synopsis....
They are awesome vehicles but will empty a healthy bank balance rapidly when they go wrong.
The V8 engine is very sturdy, but there have been reports of VANOS guides wearing and they are ££ to replace.
The Front Diff suffers a misalignment problem, some have been delat with under recall which involved fitting a CV type joint on the front prop shaft where it meets the Diff.
The ZF 5HP24 box is a known weak point, the main problem is the bearing between B and C clutch packs which wears away the O ring that seals between B and A clutches this causes A clutch slip, which the Lock Up clutch trries to control the amount of slippage, this prematurley wears the LUC friction material and trashes the box...not as catastrophic as the GM box failure, but will cost around 2K to refurb the box plus a refurbed Torque Convertor....symptoms include a 'Cattle Grid' type vibration between 35-50mph
Suspension bushes wear rapidly, esp. the rear bushes.
The rear electronics bay on the left handside of the Boot gets soaked from a leak on the rear quarter...in the best case this will cause minor electrical niggles..the worst case it will trash it costing a bomb to replace/repair.
The Cables that actuate the door handles break meaning you can't get in or out!
The radiators leak, the expansion tanks crack and the hoses split.
The PCV (Positive Crankcase Ventilation) system gums up with grud and will over pressure the Sump and blow all the oil out of the crankseals ruining the engine.
There are many minotr electrical niggles that require plugging into diagnostics to clear....I think they do it just because they miss being plugged into something as 7/10 times it is just a spurious fault.
The batteries are like the P38....once they are tired they will reek havoc on the electronics.
Other than the main bits above, they are brilliant vehicles to drive...but aslong as you are handy with a spanner, and have your own Diagnostics device, repair costs aren't to bad.....if you can't DIY you'll need a budget for repairs....
Awesome cars though....would I have anything else? No...!!!!