Vibration has me nervous

[Gus68]

Hey guys!!! I have a slight vibration which I BELIVE to be coming from the engine. It comes at about 2900 to about 3400 if I rev it in park. It also comes in whive going down the road and will make you butt tingle and things in the mirror look blury. Here's what I have done. I rebuilt my 406 that was in the car for about 7 years. No problems just rings and bearings, when I tore it down everything looked great!!! with just some slight copper showing on the front main, otherwise wverything could have been reused. My motor consists of a Scat crank and rods, speed pro pistons, file fit rings, comp solid flat tappet cam, double roller chain, All of this was reused, the only new addition was afr heads instead of the old cammelbacks, which I dont think sould matter. I reused the flywheel (dont remember the brand but I bought it new 2 years ago) The balance is stock, which I thought may have slipped but it has not, and the rubber looks to be in good shape. I had all of this ballenced when I built the motor the first time (7 years ago). I had about 50 miles on the rebuild and then went raceng last weekend. I made lots of passes and the car didn't miss a beat. nothings knocking or rattling (other than the normal lifter noise) I also have a solid motor mount in the driverside and a stock one in the pass side, same as before and never noticed anything. Maybe I am just nervous and its nothing. But I would love some words of wisdom.

[no_bite]

a good start would to get a one piece harmonic balancer.

[racecar100]

What engine are you running????

[stroker1]

Make sure your motor mount bolts are still tight. Check torque converter bolts. Check bell housing bolts. If you don't find anything, remove the bolts from the flexplate and push the converter into the transmission away from the engine. Have someone to crank the engine and see if the vibration is gone. Also see if you can see the flexplate wobbling. Make sure you are using a dowel pin in the crank to locate the flexplate. This will also help prevent the flexplate from working the bolts loose. Also make sure you have the flexplate bolted on where the raised bosses for the torque converter bolts are facing the transmission. If it's backwards the converter and flexplate will be in a bind and cause a heck of a vibration. Might also make the converter not engage the pump properly.

Also, make sure the counter balance is still on the flexplate if your 406 is externally balanced.
Check all this and repost if you don't find it.

[stroker1]

Almost forgot....Another thing to check, depending on what type of converter you are using, it might have a pilot with a removable ring or bushing on it to fit different size crankshaft pilot holes. If it is not glued on or spot welded it can come off and cause the converter to wobble and vibrate the engine because it will not be properly centered to the crankshaft.

[Gus68]

Thanks for the replies!!!! I was starting to wonder if anyone was gonna say something. Well, my converter to flywheel bolts are tight, not sure about the flywheel to crank but I know I used locktight and torqued the bolts down. Bell housing is tight and "should" be aligned ok because I ran the same tranny and converter in the car for a year or so before I overhauled the motor this winter, and never noticed the vibration before. I have yet to unbolt the converter and run the engine but will as soon as I get a chance. I will probably buy a different balencer since it is probably a good thing to have anyway, but I used the same balencer for 7 years before I rebuilt and never had a problem and it doesn't look like the ring has slipped. I am tempted to get a rubber motor mount for the driverside and see what happens. BUT if that makes it so I cant feel the vibration that doesnt mean that it is gone, and maybe something is wrong that needs to be fixed!!! I have too much money in this damn thing and being on a tight budget, I can't afford a catostrofic failure!!!!!!!!
Oh.... one more thing the vib comes on at about 2600 to about 3200 and then goes away up towards 4000. in neutral or going down the highway.

[hugger73hatch]

I had a truck once with a 383 that was doing the same thing, may have been different RPMs, but I had a cracked flexplate around the flexplate to crank bolts. Replaced the flexplate with an SFI approved and was good to go. May not be your problem, but just a thought!

[stroker1]

Don't forget, when you get a chance make sure the flexplate is facing the right direction. And make sure the converter pilot is OK if it has a bushing or sleeve on it. They can fall off without really noticing it. Or some times they get stuck in the crank and you dont know it and the machine shop removes them and forgets to tell you about it. Good luck!

[Gus68]

Hey guys!!!! I know it's been a while since I last posted but I haven't had a chance to get to my car lately. Messed with it today and replaced bothe u-joints and found that one had some broken needle bearings. I thought, THAT"S IT!!!!........ Wrong!!!!!! Still there. But while I was fixing things there has been 2 or 3 times the starter made some bad noises so I thought I would see whats going on there. I looked up atthe starter and saw that the bell housing on the tranny was cracked half way around!!!!!!!!! Well atleast I know that the motor wasn't the problem.

[Racer704]

Do you know what caused the crack in the bell housing?

[hugger73hatch]

Had that happen before too. Forgot to mention it earlier. Time for the ultra bell.

[Gus68]

No, I don't know what caused the crack. That I can't explain. Like I said earlier, I rebuilt the engine this winter and got it running a week before I went racing memorial day weekend. and ever since I went racing I have noticed a vibration. All the bellhousing bolts were tight. I am gonna take it out this week, maybe I'll see something then. I have a friend that had the same thing happen a few years ago but his broke all the way around!!!!! He replaced with another case and hasn't had a problem since. I think we are gonna weld the case and weld in some gussets for good measure. I have a friend that is a really good aluminum welder. Thanks for all the tips guys!!!!!

[eldabo]

Im not sure I fixed my vibration, but reading this thread made me take a look at some of the the things that were brought up. I found (drum rool) one missing bolt on the trans a loose bolt above that one and two missind nuts on my cross member who knows may that will fix the wha wha smooth wa wa vibration Ive been chacing for a wile . I tryed pinion angle new drive shaft it needed to be a little longer tire ballance and reballance .Its late so Ill have to wait till tomorrow to see.

David
Sorry to hijack