General Maintenance & Repairs - Bad vibration at higher speeds. Help?

first off the car has always seemed to shake a bit the faster it goes but a few days ago i swapped rims/tires on my 95Z from the stock 16s to some 17x8s w/ 245/45s up front and 275/40 MT DRs and then last night a buddy in an 02 GT and I played around a bit and did a roll from about 45mph. I barely got him up to 105-110mph but once i got to 80-90mph or so the car was shaking really bad and i backed out at 105-110mph despite having lots of straight left because it was shaking so bad. ( i just had these on my TA and it didnt do anything like this so i dont think its the tires) I already checked and the lugs are all tight and the only other thing i can think of is the D.S being outta balance. Anyone gotta any suggestions or had a similar experience? Thanks for any help!

Had similar problem with my 94z. both hubs and tie rod ends needed to be replaced. good luck finding your problem.

DS is my guess if it feels like its coming from the back. do you have a steel drive shaft? could be bent axels if you drag race often, but i would look at the drive shaft first

Mine has had a vibration since the day it came off the showroom floor. It got a lil better when I tightened up the pinion nut that the factory left a little bit too loose. Mine normally isn't bad too bad until you let off the gas at around 80 or so, it's bad on deceleration at that speed. I thinks the problem is that the 10 bolt is just a crappy ass piece o shit and I'm in the processing of getting rid of it (9" ford) Might check the pinion nut if it's coming from the rear.

DS is my guess if it feels like its coming from the back. do you have a steel drive shaft? could be bent axels if you drag race often, but i would look at the drive shaft first
yeah its the stock D.S. I dont drag it often. I know the guy that had it before me ran it 3 times at the strip. I havent run it at the strip yet and have only been in 6 or 7 street races with it, most of those roll-ons
Guess I'll try the ls1 D.S. swap again and see if that fixes it.

Towards the end GM admitied there was a problem so the last few 97s with extended warranties could actually warranty out there stock vibe shafts and get a 1LE replacement.

i got a 95 though. I took it to a shop to get a stock ls1 alum from my SS put on but they said it wouldnt fit despite several folks telling me it was an easy swap. Id try it myself but my back is still broke from my accident so i cant but im gonna get some buddies to try it again. I also have the stocker from my TA but its an auto and the LT1s a 6sp. Would it fit anyway?

I know that the shop told u that about the driveshaft but I guarantee if it is a stock driveshaft from any fbody 93-02 it will fit in any other fbody wethere its a six speed or auto there should be no issues. a while back i swapped a 2000 ss auto aluminum ds into my 97 formula 6 speed. I know this as a fact. Also your problem sounds exactly like a driveshaft balancing issue.

good deal then. I'll give it a shot this weekend. Thanks for the help guys!!!!!

if it turns out not to be the driveshaft then what else should i look for-- I know hubs, tie rods, pinion bolt........anything else?