z28ssslp

I recently bought a '97 SS 6-speed. At speeds of about 85-90mph I start to hear a rumble from the back of the car. Not sure if it is the rear wing, differential, tires(Kumho Ecsta Supra 712 Tires), muffler, or something from under the rear of the car. Any thoughts?

DonHood

That's about the speed that my driveshaft has some vibration to it. I think most LT1's have that problem.

z28ssslp

How can I fix it?

Bow94z

get the driveshaft re-balanced...thats what i always heard

blown94

Im currently experiencing the exact same problem, but it starts around 90mph and is brutal around 110 especially if you coast decelerate from there. I too have ecsta 712's, which is weird, but I have the steel d/s with new HD u-joints so I know its not those. Im going to try an aluminum d/s. Let me know what you come up with and Ill let ya know if I find mine.

DonHood

Never really bothered me since I'm rarely at that speed, but most people just buy an LS1 aluminum driveshaft instead of trying to balance the stock steel one.

350350

I have the exact same car and tires, and recently lost my '95 LT1/6-speed car to a rollover. Anyway, it had the same problem and I read here that the LS1 cars have a larger diameter aluminum driveshaft that is much less prone to vibration. I replaced my steel driveshaft with the aluminum LS1 model and almost all of the vibration went away. Not completely, but much much better. I noticed right away when I bought this '97 SS that it had the dreaded vibration that my '95 had and I plan to swap the driveshaft this weekend when I can get it in the garage. It wouldn't hurt to have your tires' balance checked too but I'll bet it's the driveshaft.

Just my $0.02.

Oh, I paid $175 for a nearly new 2002 LS1 driveshaft, I think that was about going rate 2 years ago, not sure what they're going for now.

350350

I don't get it... I can't drive mine under 100... Mine has 4.10's though

I find that I actually use all 6 gears now as compared to the 3.42's in my '95 which really required only 5 gears and 6th for gas mileage purposes. I still got 22mpg on the roadtrip home with it @ about 85mph and 2300rpm with a lot of throttle bursts as traffic would allow. It is probably still capable of 25mpg with a sedate person driving.

OK, sorry for the HiJack. I'll go back into my corner.

z28ssslp

WOW! Thanks for all of the replies. Blown94 you experienced the same thing that I do. I can power up to 110-120mph with noticed vibration, but when I coast it sounds/feels horrible. Looks like an LS1 shaft for me. 350350 keep me posted on your swap out.

SixSpeedShifter

FYI, when you get a vibration on deceleration, it's the driveshaft 99% of the time.

350350

Hey Man, I got sidetracked and just now got my car back together, and got the LS1 aluminum driveshaft swapped into my '97 SS. I ran it up to about 110 tonight on my test drive, and it was smooth as silk! I'd bet this is your problem, although hopefully you've already solved it and forgotten about it!

What did you end up doing? And if you bought a driveshaft what are they going for these days if you don't mind my asking???

Thanks,
Paul

z28ssslp

I got a price from the GM salvage yard of $200. I haven't had the time to check with them to see if they have one. But every time I hit 85mph I am reminded that I need to get on it. I am sure that the driveshaft is the problem, just don't have enough time.

z28ssslp

Well I swapped out my driveshaft and it has reduced the vibration by about 75%. I can still sence it. At least the car does not sound like it is going to rip apart.