Motor vibration at 3,000 RPM's

[DarkoStoj]

I have no idea what this could be. when I bought the 66 It had terrible vibrations and i've slowly been trying to figure it out. It seems like the vibration would occur at different rpms in every gear, but when I put in the clutch on the freeway I would have driveline vibration when the motor was at idle, so that confused me.

I fixed the driveline vibration, and when I'm on the highway with vibes I push in the clutch and they all dissapear. I've also noticed that the car vibes in every gear the worst at around 3,000 rpms. I tore the motor apart and changed the head gasket, intake gasket, exaust gasket, put in NGK plugs, changed plug wires, and just gave the car a overall tuneup. When I glanced the motor mounts and trans mounts seemed real solid. I'm stumped on this one.

 

[jasonn]

Couple of quick things to check that I've had trouble with. One time, on a car that I'd bought, had loose bellhousing bolts. Tightened them up and it worked. I've always had a vibration in the mach like this also. I just pulled that apart the other day to try a little looser converter and was looking at the bell when I took it out and it was cracked! Like a 12" crack through it all the way through one of the pump bolts! One other thing was I tried a poly tranny mount in it and it made it WAY worse so don't use one of them with a vibration.
Oh, one other thing, they don't have the wrong balancer or flexplate on the motor since the newer motors are a different balance?

 

[DarkoStoj]

Couple of quick things to check that I've had trouble with. One time, on a car that I'd bought, had loose bellhousing bolts. Tightened them up and it worked. I've always had a vibration in the mach like this also. I just pulled that apart the other day to try a little looser converter and was looking at the bell when I took it out and it was cracked! Like a 12" crack through it all the way through one of the pump bolts! One other thing was I tried a poly tranny mount in it and it made it WAY worse so don't use one of them with a vibration.
Oh, one other thing, they don't have the wrong balancer or flexplate on the motor since the newer motors are a different balance?

The first then I did when I got it was pull the trans and check the flywheel/clutch. It has the correct flywheel, and the throwout bearing was toast, so i replaced that. The pressure plate and clutch disc looked new though. The balancer was toast also, the outer ring was pushed back aboug 3/16 and was rotated about 1". I got a new one on there now.

 

[302 coupe]

I remember when we swapped a 351C into our 66 F250. There was a noticeable vibration when driving around 2500-3000 rpm. We went through it head to toe, found nothing. Then we started to think about the flywheel. We had reused the flywheel from the old engine. They were both 28 oz imbalance, so it should swap, right? Wrong. The counterbalance was in a slightly different spot, causing vibration. What was weird about it was that when it started shaking, you could mash in the clutch, rev the engine a little, let the clutch back out and it would be smooth again. Yeah, weird. We replaced with a correct 351C balancer, all is good now.

 

[WORTH]

First off Vibrations suck , if you have AC or PS, take the belts off and see if it goes away, that will atleast eliminate a couple of possibilities.

now this may sound wierd to you but you may not have a vibration problem, just a contact problem, all engines and drivetrains vibrate, but the rubbers insulate the vibration from the car, all it needs is a solid piece connecting the drivetrain to the frame and your gonna feel it. could be as simple as a fuel line, or the exhaust touching someplace.

PS. I've also had cracked brackets,(ac or PS or alternator) cause a vibration.

 

[DarkoStoj]

First off Vibrations suck , if you have AC or PS, take the belts off and see if it goes away, that will atleast eliminate a couple of possibilities.

now this may sound wierd to you but you may not have a vibration problem, just a contact problem, all engines and drivetrains vibrate, but the rubbers insulate the vibration from the car, all it needs is a solid piece connecting the drivetrain to the frame and your gonna feel it. could be as simple as a fuel line, or the exhaust touching someplace.

PS. I've also had cracked brackets,(ac or PS or alternator) cause a vibration.

no AC or PS, so I don't have to worry about that.

There is a turnbuckle that goes from a bolt on the head to the frame on the drivers side of the motor. A while ago the motor bent it so it fell off, and the motor mounts were allowing the motor to flex WAY too much. I put the turnbuckle back on, having it off didn't do anything to the vibes.

 

[John Z]

no AC or PS, so I don't have to worry about that.

There is a turnbuckle that goes from a bolt on the head to the frame on the drivers side of the motor. A while ago the motor bent it so it fell off, and the motor mounts were allowing the motor to flex WAY too much. I put the turnbuckle back on, having it off didn't do anything to the vibes.

Hmm. That should be designed to allow some rotation of the engine as it builds torque. If not it could be a source for some of the vibration! I bet if your engine mounts are allowing that much rotation they are toast!

 

[DarkoStoj]

thats the next thing I was going to do, swap the mounts. I'm not going to be able to do it for a while since I'm at school and all my tools are an hour and a half away (along with 3-4 sets of new mounts I have sitting in the garage)

blkfrd - I've heard of some people cracking bellhousings if they had a lot of torque, rubber motor mount, and poly trans mount.

 

[John Z]

thats the next thing I was going to do, swap the mounts. I'm not going to be able to do it for a while since I'm at school and all my tools are an hour and a half away (along with 3-4 sets of new mounts I have sitting in the garage)

blkfrd - I've heard of some people cracking bellhousings if they had a lot of torque, rubber motor mount, and poly trans mount.

Drive really carefully until you get those mounts replaced! No drag racing.

 

[4MuscleMachines]

I have no idea what this could be. when I bought the 66 It had terrible vibrations and i've slowly been trying to figure it out. It seems like the vibration would occur at different rpms in every gear, but when I put in the clutch on the freeway I would have driveline vibration when the motor was at idle, so that confused me.

Having owned three 351 Clevelands, I understand how you feel. IMO, they are finicky motors that can easily have vibration issues when other engines like the 302 and 351 windsors won't. All three I had during different times, and purchased from different people had the same vibration issue.

The first one turned out to be the flywheel. The Hayes book stated it was the correct one, but when I had the original resurfaced and installed, the vibration went away. The second engine had the clutch and pressure plate changed to make the vibration go away. I am now on my third 351C with the same issue. Funny, it is the most expensive build by far and it has it the worse. Still haven't found the problem. Just keep looking, I am going to borrow a new alum flywheel and clutch assem and swap to see what happens. Next I will change the bellhousing back to oem.

 

[DarkoStoj]

Having owned three 351 Clevelands, I understand how you feel. IMO, they are finicky motors that can easily have vibration issues when other engines like the 302 and 351 windsors won't. All three I had during different times, and purchased from different people had the same vibration issue.

The first one turned out to be the flywheel. The Hayes book stated it was the correct one, but when I had the original resurfaced and installed, the vibration went away. The second engine had the clutch and pressure plate changed to make the vibration go away. I am now on my third 351C with the same issue. Funny, it is the most expensive build by far and it has it the worse. Still haven't found the problem. Just keep looking, I am going to borrow a new alum flywheel and clutch assem and swap to see what happens. Next I will change the bellhousing back to oem.

you have a lakewood bellhousing? Maybe check the runout, and see how far you are off

 

[DarkoStoj]

You might be right. I could see the opposite being a possible problem too...poly engine mount and rubber trans mount.

It's puts a big smile on your face when you conquer those very annoying vibrations. I hope you get it fixed soon!

I wouldnt think that would be the case. With a rubber motor mount and poly trans mount the motor will twist in the mounts creating pressure on the aluminum bellhousing to crack. If you flip it around with poly motor mounts and a rubber trans mount, the rubber trans mount would be able to flex, and the poly motor mount wouldn't allow as much flexing.....that make sense?

I had a friend that had a built 454 in a toyota landcruiser, and he broke TH350's all the frickin time. He could never figure it out until I crawled under there and saw he had a SOLID trans mount with rubber motor mounts.....

yea and fixing vibes makes the car that much more enjoyable to drive....I hope its the motor mounts

 

[jcode68]

DarkoStoj - just wondering if you ever got your vibration problem solved? I am dealing with same symptoms you described in your thread. I have rubber engine mounts and a poly trans mount for my T5. I was starting to think it may be the flywheel I bought is out of spec - I did after all only pay $90 new off ebay for billet steel. Before I drop $240 for a new Ford Racing unit, I thought I would follow this thread up. Will also try replacing the poly mount with rubber first as well.

 

[DarkoStoj]

DarkoStoj - just wondering if you ever got your vibration problem solved? I am dealing with same symptoms you described in your thread. I have rubber engine mounts and a poly trans mount for my T5. I was starting to think it may be the flywheel I bought is out of spec - I did after all only pay $90 new off ebay for billet steel. Before I drop $240 for a new Ford Racing unit, I thought I would follow this thread up. Will also try replacing the poly mount with rubber first as well.

ugh, I started thinking about that car today and I almost posted a thread called "anybody ever regret selling a car so bad you get stomach pains thinking about it"

yep, thanks for bringing up bad memories

 

[jcode68]

My bad.
Did you get to the bottom of your vibration problem before selling the car?

 

[truck90278]

One thing not mentioned in any of the posts - May want to check the driveshaft for out of balance. I've seen many times fibration at highway speeds caused by an out of balance driveshaft.

 

[Iggyshane]

i was also thinking your drive shaft could be out of balance.