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HotRodV6
11-21-2015, 10:45 PM
Ok, i recently bought a 97 Firebird Formula with 66K original miles. Car has sat for the last two years or so due to a bad fuel pump and then slashed tires.

The car is an auto with stock converter, rear axle has been rebuilt and has an aluminum rear cover and i was it has 3.73 gears but after driving it, its got 4.10 gears not sure if the locker is stock or aftermarket at this point. The rear suspension has granatelli motorsports lower arms, Hotchkis panhard bar, welded in subframe connectors, eibach pro kit springs and bilstein shocks. I think the sway bars are stock with urethane bushings, urethane trans mount and maybe engine mounts.

The engine has the LT4 hot cam kit with crane 1.6 roller rockers, BBK shorty headers and stock dual cat y-pipe and a flowmaster catback with a cutout. and a moroso CAI, EGR deleted as well. Rest is stock as best i can tell.

The car has 17x9.5 ZR1 style wheels and i just put a good used set of Cooper Zeon 275/40 tires, The vibration isn't there when cruising, but as soon as you give it gas to accelerate it shows up and seems to be related to speed.

I'm thinking maybe its u-joints but with only 66k miles on the car i wouldn't think they'd be worn out, but who knows. Also i don't think its anything in the rear axle as usually that would be noise under cruise or when you let off the gas.


Just looking for some advice as to were to look or if anybody has ran into this problem before.

Thanks for the help.

tleed
11-22-2015, 08:20 PM
Could be the tires from sitting so long I would also check the driveshaft and have the wheels balanced if the tires are ok.

HotRodV6
11-22-2015, 08:27 PM
Well I just had the tires put on and balanced so I don't think it's that as usually tires will vibrate at certain speeds not just under acceleration. But anything is possible.

The car has an energy suspension trans mount so that is gonna cause some vibrations as well.

Injuneer
11-22-2015, 10:30 PM
Stock torque arm, or aftermarket adjustable?

HotRodV6
11-23-2015, 12:28 AM
Stock torque arm, not sure if the bushing is stock or poly.

Injuneer
11-23-2015, 04:50 PM
Vibration under load can be due to the pinion angle being set incorrectly, or the torque arm moving in the bushing. A replacement poly bushing is typically a one piece bushing, that slides over the end of the torque arm. The OEM rubber bushing is "split" with one half riveted to each half of the clamshell mount.

Check the torque arm and see if it is possibly bent.... it's fairly thin stamped sheet metal.

HotRodV6
11-23-2015, 05:25 PM
Vibration under load can be due to the pinion angle being set incorrectly, or the torque arm moving in the bushing. A replacement poly bushing is typically a one piece bushing, that slides over the end of the torque arm. The OEM rubber bushing is "split" with one half riveted to each half of the clamshell mount.

Check the torque arm and see if it is possibly bent.... it's fairly thin stamped sheet metal.

I was thinking the torque arm and or mount myself, gonna check that this evening, as i was going to install a poly bushing if it still had the stock rubber one.

popo8
11-23-2015, 07:08 PM
Any chance it is something we could notice in a video? Does it level out or get worse at any certain speed, rpm...etc?

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Not Dave
04-23-2016, 06:49 PM
Did the issue ever get resolved? I have vibrations in my car also under accel and decel.

I just ordered a Three Rivers 12564004 used driveshaft off eBay, I've read that is a good upgrade for weight and vibration reduction. My drivetrain is also stock. The only thing I replaced when I got the car a year and a half ago was the broken trans mount with a new rubber one.

HotRodV6
04-23-2016, 06:54 PM
No it did not and then in Dec last year i sold the car.