Bad vibes

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aaronk785

aaronk785

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Just got my 360 in my dart. Runs strong and doesn't miss. Has the correct balancer and b&m flex plate. Doesn't vibrate in neutral when I rev the engine. Going down the road about the first couple miles when I floor it, it vibrates like hell feels like the trans is going come through the floor. Drive a ways further and floor it not as bad. Go maybe 6 or 7 miles floor it and vibration is totally gone. Let the car cool down and same thing all over. Has new motor and trans mounts and nothing is hitting anywhere. Never did this with the 340 it just had in it. Please give me your opinions. Thanks.
 
First thing that comes to mind is U-joints. Especially since they smooth out after awhile.

Try coasting in neutral when you feel the vibration to see if it continues or not.
 
never heard of temp. playing a part in vibration.u joints,driveshaft or pinion angle do.i would check those,ask me how i know
 
If it feels that violent, I'd definitely be looking at the driveshaft/ujoint. Not the same, but I have experienced what you're talking about in a cherokee after I dropped a new engine in. It'd bang around like I was missing a motor mount. Turns out some of the bellhousing bolts had come loose and it was allowing the engine/trans to sag. After you'd drive it a bit, it'd settle down as I'm guessing the trans would "align" itself. I wouldn't have easily caught except it finally struck the crank sensor which shut it down completely. Once I saw the gnarled sensor, I crawled underneath and noticed the 1/2" gap at the bottom of the trans/engine (well bottom side). Once I retightened it went away.

Not sure if that could be your issue, but it's easy to check.
 
You might want to check bell housing bolts to see if they are tight.
 
Thanks everyone. I will pull the drive shaft tomorrow and check it out. I always try to make sure the u joints are seated properly, but it can happen, it has before. I will also check the pinion angle. I was also going to check the bushing in the tail shaft for excessive play. Thanks again for your replies.
 
Make sure you put a drain pan under the tail shaft. Ask ME how I know
 
Had the same type of problem,took me a week to find,it was the clutch on fan,eliminated clutch with clutch less flex fan hope this helps
 
Thanks for all your replies. Replaced u-joints and trans bushing. Checked al bolts to bellhousing, took it for a spin, no difference. Switched out the fan and boom, 95% better just a hair of vibration at high speed. Thanks Buddyroe. I would have never guessed that would vibrate that bad. So I double checked under the car and something didn't look right with the driveshaft. So I pulled it and noticed the u-joint caps were not aligned, or out of phase. I had a machine shop shorten this 10 yrs. ago. Last time I use them what a bunch of crap. And its not twisted because the rear joint is ahead of the front one. I would guess its of 10 to 15 degrees. So a new shaft and I should be good. Thanks again.
 
aaronk785 said:
So I pulled it and noticed the u-joint caps were not aligned, or out of phase. I had a machine shop shorten this 10 yrs. ago. Last time I use them what a bunch of crap. And its not twisted because the rear joint is ahead of the front one. I would guess its of 10 to 15 degrees. So a new shaft and I should be good. Thanks again.
Click to expand...

WOW. You don't hear about that very often. But that WILL DO IT!! LOL
 
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