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jim, sounds similar to what i have. my vibration is a rapid on/off kind of thing. one second of vibration; one second of smooth running etc, at all speeds between about 60 and 70. is yours on/off or does it constantly vibrate? mine will do this even if i coast in neutral. everyone thinks it is wheel balancing, but i have had that done twice, including once with the fancy machine that duke suggested. they swear it is not the wheels. anyway, i think i will have the wheels balanced on the car etc, but before i do that, i will see if i can substitute wheels with another owner for an hour on a saturday to see if the vibration goes away. it seems that i will have to be 100 percent sure it is not the wheels before i go to the expensive stuff. what have yo done to rule out a wheel problem?
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Re: Drive line vibration
Two other things can contribute to C1 driveline vibration - yoke angle, and the yoke itself. The C1 U-joints run at very extreme angles, and many have lost the shims over the years between the top of the trans crossmember and the bottom of the frame "X"-member where they bolt up; mine smoothed out very nicely with about 1/4" of shims (washers) at each of the four bolt locations. Also, many yokes have been replaced with the wrong passenger car part, which tends to eat up the rear bushing (and sometimes twists the splines on the output shaft); the (wrong) passenger car yoke is about 3" long, and the unique Corvette-only yoke is 4-3/4" long. The Corvette used a longer yoke due to the greater fore-aft excursion of the yoke with rear suspension movement as a result of the extreme driveline angles. -
Re: Drive line vibration
john, does what you say hold for c2 cars also? can the vibration as you described it be the on/off type that i have?? or would it be constant at a given car speed??Comment
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Re: Drive line vibration
Werner -
The C2 driveline is fixed (no relative motion), so I doubt that driveline angles are involved; sounds more like an induced harmonic issue. A frequent source of C2 driveline vibration/noise is the bushing arrangement between the front of the diff nose mounting bracket and the frame; if the bushings have deteriorated, the stackup becomes loose, which can affect the rear U-joint operating angle and/or allow hard contact between the bracket and the frame. You might also check the trans mount for separation.Comment
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Re: Drive line vibration
When I first bought my 74 back in 77 with 29K miles, I didn't know much about Vettes. I had a buddy that had a Plymouth Cuda with a 340, and he had a bad clunk in the rear end...and we replaced the posi unit. It had wallowed out the cross shaft hole to oblong, and the result was a substantial clunk in the rear upon acceleration/deceleration. I drove my 74 for years thinking I one day had to pull the pumpkin and fix it. I had learned exactly how to feather the throttle to prevent the obnoxious clunk. Well, somehwere around 1984, when I really began restoring the car, I replaced the $4 cushions and the clunk was gone.....at which point I felt like a complete idiot for not even checking this for years to correct. Kind of like the pulling steering on vettes is caused by incorrectly centered PS valves more than alignment problems....live and learn...the more you work on them, the more you know!....CraigComment
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Re: Drive line vibration
The tires are new and balanced, that took out a front end shake, this is definately coming THROUGH the transmission to the shift leaver, it's not a shake or shimmy, but a vibration too fast to be a rattle. I'm leaning towards the trans. output shaft bushing theory, due to this column advise and the drive shaft balancers misinterpurted comment about replacing a bushing. Thanks for the help!!!Comment
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