I have a 1970 98 LS Hardtop named Cindy. I've had her for 3 1/2 years and she has always had a weird vibration that feels like it is coming through the seat at acceleration. Like a pulsing when initially accelerating. Less in a straight line or turning left more when turning right. It also isn't always constant, usually only after a complete stop not a California stop. It does not vibrate the steering wheel. Since I've owned her I've replaced all four shocks, all front bushings, center link, stabilizer links, and tires. I've changed her tranny fluid, differential oil, brake fluid, and of course the oil several times. Nothing was remarkable about any of the fluids. She has still done it even through all of that. I did check the u-joints by trying to move the drive shaft, it is rock solid. She has minor leaks around the engine and driveline, all oil no tranny fluid. I have seen a small amount of dampness around the front of the differential but it may be blowback from engine oil. She only has 67,000 miles but was not driven more than 2000 miles between 1985 and when I bought her in 2016. She was well maintained and looks good just not well used as her original owner was elderly at that point and the second owner just didn't use her much. I have the FSM but it doesn't really talk about this specific issue. If anybody else has ever noticed this it would be a great help to know what they did to fix it or if I should even worry about it.

Thanks,
Steve

 

Forgot, I have also repacked the bearings.

 

Low frequency or high frequency vibration? Does it have a limited slip differential? If yes it may be clutch chatter in the differential which can often be solved with limited slip additives.

If no, the u- joints may be sticky even though no play is detected. The driveshaft would need to be removed to check them for sticking/binding.

Good luck!!!

 

Thanks for the info! It's like a quick pulsing through the car. No it does not have limited slip.

 

I would replace the ujoints.

 

Check the U-joints. After driving for a bit, see if any of the wheels get warm, I'm thinking about a drum out of round or disc out of parallel. Can you feel any pulsing on braking?

 

If you do the u-joints consider having the drive shaft glanced at the sane time.

 

Thanks for all the input. I haven't had much chance to take her out lately, but I will definitely check the U-joints.

 

I've seen a bad harmonic balancer do similar things in a Ford. I would look at this but more likely something like a u joint. Turns made no difference in the ford. It was a just off idle thing you felt starting out and when you looked it wobbled when the motor was running

 

Would never have thought about a HB. I'll have to look once she's running again, lost the original starter yesterday.

 

Consider keeping the original starter core for date codes etc.