Hi Guys, Although I know how to wield a spanner and used to work on cars, but as a Brit from over the pond I have little knowledge of American muscle, but now I spend 6 months in Florida I 'bit the bullet' and bought a 1996 5.7 Z28, and humbly ask for some advice.
At around 75 mph I am aware of a vibration which increases with speed. It is not in the steering so I have eliminated wheel balance but figure it could be from the transmission and in particular the propshaft. Now I looked on Ebay for a replacement and found a company which replaces the two part prop with a single length one, and ask members if this is a better idea ( in which case why did GM not fit one originally )?
I guess I should think of replacing the spark plugs too, but the urbanization we live in doesn't allow us to work on cars , and ask if anyone in the Ft Myers area of FL who has the facility and knowledge to help with this difficult task in exchange for dollars !!

 

There are a few things I would check first:
Try rotating the wheels/tires (front <-----> back) and see if that changes anything. If it does, check the tires and wheels for excess radial (roundness) run-out. Use a dial indicator on the center of the tread while spinning the wheel by hand. The manual states the wheel run-out to be less than .03" ( add some for the tire). Look for big differences between wheels/tires. Check for lateral (side-to-side) run-out, which might be cause by a bent wheel (again .03" limit).
Check the u-joints for looseness.
Check the transmission mount. Those can look normal when they are actually separated. Try lifting the transmission tailpiece with a pry bar or large screwdriver.

 

Thanks for the advice Gary, but the steering wheel doesn't shake, it really doesn't feel like a wheel/tire problem, ( it has 5 spoke Corvette chrome wheels ) but I'll do as you suggest just in case. I'll also have a look at the transmission mount If it is the transmission, have you heard of this modification to a one piece prop ?

 

Hi,

If the steering wheel doesn't shake, that only means that your front wheels aren't the problem. Swap the wheels front-to-back to see if it's the rear wheels.

The two-piece driveshaft wasn't used in fourth-generation Camaros (1993-2002). The single-piece upgrade you're seeing is for fifth-generation (2010+) models.

It is possible that your driveshaft is out of balance, but LT1 cars (like yours) had steel driveshafts and are not known to have this issue. I'd focus elsewhere first.