Wondering if anyone here has had a vibration from thwir slant at around 2500 rpm. Its a 1969 engine. Runs great idles smooth ect. It is in a truck with np445 transmission
The vibration is worst driving at 55mph. It is not nearly as bad holding the engine at 2500 in neutral. Can engine vibrations combine with driveline vibrations?
Thanks mike.

First I would do a SERIOUS check of the driveline universal joints. Any loosness is bad. You said it is at 55 mph, and it probably changes if you are accelerating vs. decelerating? I had a 75 Valient that would only do it in a slight turn at 55. Yes, vibrations can combine. After that, others here will give you more troubleshooting ideas. My 2 cents.

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"Louise", a 1976 Dart Custom project, (now sadly reverted to being just an "organ donor" to our other project Darts.)

Check for slop in tail shaft bushing that the front yoke slides into.

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67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

The driveline vibration is likely coming from a loose slip joint in the drive shaft it has worn splines. At the 55mph if i shift to neutral the vibration is nearly gone. Virtualy no different on or off gas. Also if i speed the engine to the 2500 rpm with vehicle stoped very little but some vibration. If coasting at 55mph in neutral i speed the engine to 2500 the big vibration is back. Someone did tell me forged crank slants have a bit of vibration has anyone here heard that?

No... I would not think so as a result of an unbalanced rotating assembly anyway. Cylinder misfire?

I would like to hear more about what this vibration is like.. Is it shaking the mirrors? Or what I would call a low frequency. If it a high frequency, you hear it almost more than you feel it. I am guessing you are speaking of a low frequency vibration where you feel it through the seat, and maybe the steering wheel or through the floor?

Finding this may be a process of elimination, Starting with the easy stuff first. I know that sounds rather obvious..

What vehicle is this in? NP445 would suggest a mid 70's truck? Can you describe more about when the vibration first shows up? Such as between 30-60mph it vibrates unless I have the clutch disengaged and or coasting in neutral. Is there an RPM range that it shows up most notably? What happens if you coast down from 50MPH in neutral, and engine at 2500? When (at what speed) does the vibration go away?

Only guesses I have at this moment that could be engine related: collapsed motor mount causes something to rub, like an exhaust pipe, or I don't know what.

Can you locate the direction the sound is coming from? Front, rear, or center? Left or Right?

I just got in from working on it. I was a low frequency vibration. And you were right i did notice a broken motor mount. Most of the vibration was coming from a bad power steering belt i noticed the ps pump shaking at 2500 rpm took the belt off and vibration gone. The belt was wore thin in one spot so tuning the engine by hand the belt would be tight like guitar string one spot and lose another spot. Im glad it was an easy fix. Thanks for directing me to the bad mount.
Mike

Good to hear you got it fixed.

Cool!

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"Louise", a 1976 Dart Custom project, (now sadly reverted to being just an "organ donor" to our other project Darts.)

Wow that's crazy I had never heard of of thought of that.

Greg

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http://www.youtube.com/hyperpack

It's funny, I see that type of vibration in lawn mower decks all the time, because of a bad belt.

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2 Mopars come with Spark plug tubes. One is a world class, racing machine. The other is a 426 CI. boat anchor!

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