pulsating feeling when at 45 mph

[4404spdcharger]

Just got the 68 440  Charger RT back on the road after a engine freshen up and dyno run.  Runs great but at around 45 mph in 4th gear there's pulsating sound that I can feel too.  I had the front end aligned (was out just a bit) and the car tracks better but the same pulsating noise/feeling is present.  Goes away if I put the clutch in or go above 50 mph.  Road surface doesn't matter.    Haven't had this before and I've owned the car for 14 yrs. Any ideas?

[c00nhunterjoe]

Tires? Out of balance or flat spots?  U joints?

[Dino]

Check the u joints first.  My car got a little noisy one day and a few days later the rear u joint snapped.  Good thing I was still close to home so I could limp it back.

[BSB67]

Just got the 68 440  Charger RT back on the road after a engine freshen up and dyno run.  Runs great but at around 45 mph in 4th gear there's pulsating sound that I can feel too.  I had the front end aligned (was out just a bit) and the car tracks better but the same pulsating noise/feeling is present.  Goes away if I put the clutch in or go above 50 mph.  Road surface doesn't matter.    Haven't had this before and I've owned the car for 14 yrs. Any ideas?

You need to get more specific in the symptoms for us to better diagnose.  Does it do it at 45 mph in 3rd gear.  Does it do it at 35 mph in 3rd? Is it pulsing or surging.  You should be able to pin point it to: engine, drive train, or car.

[John_Kunkel]

Probably surging due to a lean cruise carb setting. Try richening the idle mixture.

[BSB67]

Probably surging due to a lean cruise carb setting. Try richening the idle mixture.

Yes.  And you can really feel too much timing in the form of surging in a stick car as well

[4404spdcharger]

The timing is 15 BTDC, 36 all in.   I'll try 45 mph in 3rd and the other suggestions to narrow down the source.  I'll definitely have a look at the U joints.  The tires are Goodyear T/A bought in 2001 so Discount Tire would not service such old tires despite I've only put 15,000 miles on them and the tread is fine.  Looks like some Coker redlines are in my future this summer.

[cudaken]

Flat spots on tires feel like a thumping, not a surge. But, you will notices it more at a lower steady speed. When I hammer my Road Runner, can't say I notices it, but I am busy at the same time! 

Cuda Ken