Problem issues with the GTO.
1. Suspension. Regardless of who you ask, ALL will agree that the stock suspension is simply put.... GARBAGE. It's a decent street car, handling/comfort balance is well struck for an OEM setup, but premature Shock, mount, and bushing failure could result in expensive fixes further down. FIX: Get a pedders Street II/Track II or equivalent package from Wretched Motorsports for approx $2K(I'm plugging Rob here, as he's a great guy and an asset to this forum). He does offer a GTO specific Problem Package that replaces all the OEM parts that most commonly break down. I think that package is just under a grand.
2. Tranny. Numerous members (including myself) have had rear end/tranny failures. The problem will arise early on, before you hit the 36K mark, and will start off as a whine. From what I'm gathering, the problem seems to be that the rear end has in certain cases improperly cut gears, that place forward stress on the driveshaft, causing bearing and synchro failure in the M21/T56 tranny. (Someone message me/post why they don't call the M21/T56 the same, or why they're different). FIX: Under warranty, they'll simply replace rear end, as well as tranny. Another route is to get a different gear set for the rear, relieving the stress of on the shaft, and netting some performance benefits.
3. Belt/Tensioner. A common problem for ALL LSx Engines, and GM in general. Premature tensioner failure ($80) will result on belt damage and a loud squeaking coming from the engine bay. It'll sound as though you're hiding a 8 foot cricket under your hood. FIX: Dealer rarely questions this problem as it's well known and documented, or if out of warranty, simply replace belt and tensioner.
4. Brakes: Only if you're a track whore... like me... you will find the OEM and most aftermarket pads/rotors to be inadequate. I've yet to find a decent pad that will survive a day at California Speedway in Fontana.... and I've tried many. The rotor temps sky rocket and pan fry anything on the caliper. My last hawk pads had the paint burned off. yes, I said BURNED. lol. 1100 degrees are easily achieved. FIX: Brake Rotor Ducts and strut mounts run approx $400, or don't race. lol.
Other than that, there's nothing but smiles and miles to be had from this car. Now, every car, make, model has it's own issues. GSX Eclipses shredded transfer cases, WRX's had weak 2nd gears and Cylinder 3 failures. Every performance car you look at will come with it's own can of worms, and all problems are amplified by performance vehicles due to the amount of stress and driving conditions placed upon them. No one buys a GTO and putts around in it. That's why they sell Accord's, Camry's and Malibu's. All the GTO pitfalls are known, and preventable. Not to mention, that all are reasonably inexpensive. GTO's, IMHO are THE best full sized 2+2 ever made. Think the 612 or Maserati is faster on a track.... I haven't been passed by one yet, and if you think the GTO has problems, those cars will be a moot point. Let's not even get started on the GTR. lol.