I have a 67 Rally Sport Convertible with a 327 and a powerglide trans.

At about 45MPH ONLY I get a shake and shimmey in the suspension, but at speeds below, perfect ride. In fact, at 50MPH -70MPH not present and car rides smooth, tight and dead straight. Front end is totally brand new-as are rims and tires? Is this just the life of a convertible from the 60's?

thoughts... please

thanks
JL

I assume your tires are properly balanced and the rims are true, and your drive shaft and axles are straight.

Do you have the 4 "cocktail shakers" in the fenders?

If all else fails, don't drive at 45 mph. :D

Yes on the cocktail shakers...new tires and rims properly speed balanced. as far as the drive shaft and axles not sure? would that cause shaking problem at just one speed and then go away at higher speeds?

thanks
Joe

Depends on the defect of the axle or drive shaft, but yes.

Different results happen with defects at a various frequency and modulation. LOL. Had to use big words.

I had a vibration at a certain speed on my 327/pg combo too. It started out with lots of vibrations all over the place. changing a bent rim and an out-of round tire fixed most of them. Some went away with some unbent fan belt pullys, but the last one came from a bad harmonic balancer.

That sounds to me like a driveshaft issue. I would start by checking and or replacing the u-joints. If that doesn't help, have the balance checked. I have driven many vehicles with bad u-joints that will only shake at one speed. Above and below that speed is fine.

I bought a new repo rallye rim and had it balanced. Trouble is, the bore is slightly off center, but the wheel is lug centric. The wheel and tire was balanced on a bore-centric machine, so I'm still a little off. Only one of the 4 wheels is that way, the other three were both bore and lug centric!