Pulled my 76 out of storage today took it for a god run, I have a shake when taking it up over 60MPH and worsens to the point I have to back off when pushing it up to 70mph .
I have pretty much replaced everything in this car other than the engine, I was thinking about shutting the car off at 70mph to see if that would diagnose a hamonic balancer problem but wanted to wait and see what you guys think.
Anyone have a way to check a balancer properly ? That would help prior to just ordering a balancer.
Thanks
Eric

 

Probably a bad tire.

- Eric

 

Thanks Eric, I'll have a look at them, I replaced all 4 cragars with new ones last summer also 4 new BFG's shoes, I just took the car out 2day drove it like a teenager ya know, first day out. I'm really leaning towards the balancer, however a tire would be the first place to looksee' as you mentioned. I suppose a weight could have dropped off as well. I'll report back soon.
Cheers
Eric

 

tire is far more likely
new is not equal to perfect, so don't rule out new parts as trouble source

get to your shaking speed, put trans in N and turn off the engine
w/o the engine running, much will be eliminated as a possible vibration source.

When done analyzing, restart the engine and put it back in gear and proceed.

The car will fly along nicely in N, typically with diminishing speed unless going down a steep hill. Which would be a bad place to perform this test.

 

Everything but the motor replaced? Would that include the motor mounts????

 

Thanks Octania, I will do the test you mentioned just to eliminate the balancer, the tires are seem ok with the weights still in tack.
Rj , I replaced the motor mounts during the header install last summer, the tranny mount was done as well after the torque converter swap.

I hope its not a new tire that has flat spotted over the winter, the car was parked on top of home made wooden ramps on all four corners.

I'll take it out again tomorrow when the temps get up past 10 deg and report back.
Thanks guys
Cheers
Eric

 

Trans mount was going to be my next guess... I have one thats been driving me nut also best of luck!

 

Ding ding ding ding.
Pump the tires up nice and full then drive it at lower speeds for many miles. I bet that vibration will go away. Flat spots don't tend to be permanent.

 

Balancer would show at high RPMs, not necessarily road speed, yes? Does it vibrate right before shifting? If not, it's probably not an engine issue. How are the tie rod ends and ball joints? Strange that it would happen while it sat. Check the sidewalls of your tires. Are there any undulations? Might be a slipped steel belt.

 

I had the car out most of the day yesterday, the temps went up to 18 much warmer than when I took it out ..3 then went to 10.
Defiantly the tires guys as you all mentioned possibly the cold temps when I first took it out as well.
The tires were a few pounds under pressure after driving on Saturday when cold, I topped them up after driving about 50 miles on Sunday the temps were nice and warm, took it up to 80MPH wow no shake.
I was about to order a new balancer on Saturday morning, happy I didn't now, saved a few bucks .
Thanks to all,
Cheers
Eric

 

You're welcome.

 

You need to check your tire pressure with them cold, before driving. As you drive and the tires warm up the air will expand and show a higher pressure, however they will be low when cold.

 

This winter I had to park my car out in my driveshed about 15 miles away not heated. The tires didn't appear too low, ( but my eyes aren't so good anymore haha) but after getting it going without checking pressures I just drove it the 15 miles home, at that time I noticed the bad shake.
Next year I will definitely check the pressures regardless of appearance. Put around 30 psi to start out, then allow them to warm up during a cruise. At that point I will recheck again warm.
Great advice!! I will do that next spring.
Thanks Eric,
Cheers !!
Eric H

 

One of the things I do when putting a car in winter storage is to inflate the tires to the manufacturer's max. As temperatures drop, so will the tire's pressure. Plus, the more air that's in them, the better off you'll be if any of them have a slow leak. And the higher the pressure, the less they will flat-spot.

 

If those particular tires have shown a tendency to flat-spot, there's nothing wrong with filling them to 35psi for the first 20-100 miles, to help them get back into shape.


If you're not driving it, there's nothing wrong with filling them higher, like to 40 or 45psi.

- Eric