Ok so my Z has had a vibration in it since i got it, I know it's not the wheels and tires(just balanced by myself) but i did put a new pinoin and output shaft seal in the car, and the output is leaking again. My guess to the vibration is
out of balance driveshaft
bad rear end/needs rebuild
bad motor or trans bushings
bad transmission output shaft?

I also put a new torque arm mount bushing on it, but the car shakes really hard off throttle and not on it. and if you gradually come up to speed it's not as bad but nailing it and letting off it's horrid. It feels like a whoop i guess you could say, like it's the DS but i'm not really sure.

mainly posting to see if anyone has ever had this problem or something close to it.

How and what can i check without spending a ton of money to eliminate small things?

 

Had the same issue on the highway... i had my tires checked and balanced which didnt help but i did end swapping out the shitty steel driveshaft for an ls1 aluminum driveshaft which helped out alot and can barely notice it now. This a very common thing on lt1s and a good idea is to swap driveshafts for an aluminum one which you can find cheap $80-100.

 

The stock steel driveshaft is known for bad vibration at 80mph and above. Some people have tried rebalancing but, nothing seems to work. If your car isn't making a alot of power I would suggest a LS1 alumnium drive shaft. They're 100 bux and they'll free up some weight off the driveline. The DS is the most frequent cause of high speed vibration in an LT1 car.

 

Cool, I'll be picking up a ls1 DS, only diff is what make sure it's a m6 DS right.

 

I've had my 97z28 for 5 yrs now and the whole time it had a bad vibration above 85mph. I knew it had a bent steering knuckle when i bought it. so i thought that would fix it. No. Got some corvette wheels on it and still no different. so i just never went over 86 mph. One day the motor dies at 197k miles and time for a lt4 swap. I have the driveshaft balanced, which costs almost as much as a ls1 driveshaft, and they re-weighted the driveshaft. So now instead of vibrating at 86 it's now at 91. However after reading a few posts like this one i ordered a ls1 driveshaft and had it in and done in well less than an hour. Moment of truth...4th gear well over 100mph and smooth. I cant believe it. Maybe i won't sell it afterall?

 

As mentioned, LS1 aluminum driveshaft is a very nice improvement, BUT also check/replace the U-joints, they are not expensive. I put in an aluminum driveshaft without replacing the U-joints and soon got a bad vibration, one of them was shot, it had lot's of play... so replaced both for insurance and been vibration free ever since.

Lol...just noticed this thread is from 4 years ago!

 

When I had still had my 97 camaro it did not really have this problem it had the steel driveshaft. I am not sure what made it.
All I can say is to try rotating the driveshaft by say 45 degrees at the transmission, but keep the driveshaft aligned the same at the differential. If that does not help rotate the diff end 180 and repeat.

 

I seem to have the same issue with my 1997 SS. Stock steel DS. Lowered on Koni STR-T/Strano Springs (mild lowering 1.2" approx.) Seems to start at 85 - 90 mph regardless of gear and especially at mid/high rpm. Shakes the centre console pretty good. Stock torque arm. Would a mild lowering cause this without an adjustable torque arm?

 

If your wheels are straight and neither of the axles are bent, more than likely it's the driveshaft. There was a TSB about this waaaaaaaaaaaaay back when, but is no longer valid since these cars are no longer under factory warranty. It called for the replacement of the steel shaft for the 1LE aluminum. I had it done (had to fight the dealer even with the TSB in hand) and it made a world of difference. You can also take your car to a chassis shop and they may be able to tell you more.

 

Yeah, I saw that. Makes me wonder why the original owner never handled that under warranty. Although, not everyone takes their car up to those speeds. Fresh rubber and recent alignment, car tracks very straight. I'll be heading to a driveline shop - thanks.

 

OP

Lowering "may" have affected DL angle. DL angle being off can cause vibration at Hwy speeds+. Adding or removing a shim on rear tranny mount would fix if that was the cause

As SS RRR notes it certainly could be a drive shaft that had balance issues new or was not the best spec for the gearing/RPM/Tire size the F-body has. SS RRR notes a TSB fix to another, better balanced, GM drive shaft

Ideally the DL shop you go to will find/fix the cause

 

Can I take that to mean that I don't need an adjustable torque arm to fix the high speed vibration? That would be great. I don't think the angle would be off by much with strano springs and koni struts.

 

IDK if a adjustable torque arm will resolve your vibration.

First the shop, or you, need to determine if your DL angle is within spec by measuring it. Angle finder works. Google "how to" measure DL angle. Car needs to have suspension loaded to do this so either block the tires on something so car is high enough for you to get under it or take to a shop with a lift the wheels sit on to measure DL angle

As SSS RR mentions....it could be your DS is out of balance...but again 1st thing to do is check if the DL angle is within spec. Rear Suspension mods affect DL angle.

 

You can also take your DS to a DS shop and have them spin it to see if it's either bent or out of balance. They also may be able to fix it for relatively cheap.

 

I had the same issue above 85-90mph. LS1 DS solved the problem.

 

my driveshaft vibration I dealt with also almost made me sell my car lol

 

Since it messed up the output seal of your trans, that should point you directly to the DS as the issue.

 

As I hate when threads are never updated, here's my 2+ year update to close this one out.

I replaced the factory AAM steel DS with an 3.5" Aluminum DS - no change.

Had the tires balanced - no change.

It ended up being the factory harmonic balancer, when I looked at it up close, I noticed a slight amount of rubber separation. I setup my cell phone camera and revved it in neutral and sure enough the shake, rattle & roll was from the harmonic balancer! I replaced it and my issue was resolved. I think it's a case of age and not necessarily mileage as my 97 SS had less than 70,000 miles on it at the time.

 

Could you further explain the type of vibration you were experiencing, by what ur saying I think it would not be related to mph but rpm instead.

 

I originally thought it was speed related ,but it was more so mid to high rpm shake through the centre console area prior to replacing my harmonic balancer.