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bigmal

Chasing a Vibration - Flex Plate?

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4 hours ago, det0326 said:

Mal

In this video I assume you have the rear axle on jack stands and the whole drive train is turning. Is this correct?  Also is the vibration as noticeable with just the engine running? 

That's a pretty big vibration the way the steering wheel is vibrating or is that just a nervous camera . 

Yes, this is with the rear axle on stands. And no, my hand isn’t shaking. The vibration isn’t as severe with the engine in neutral but it is at the same RPM. Thanks 

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3 hours ago, Shep69 said:

Shit that’s a bad vibration  Mal the way your steering wheel is moving. 

That’s got to bloody frustrating. I gather you have eliminated the wheels and tail shaft by removing them and running it up on stands. 

I haven’t removed the wheel or tail shaft. I didn’t know you could run it with the tail shaft out. I thought it would loose transmission oil.

Can you run it without the yoke in? If so I will definitely try that. Will also remove the wheels as well.

as it seems dependent on engine rpm not wheel speed I didn’t think it would be rear of the transmission but it’s certainly worth eliminating everything that is easy before stripping the engine.

Will also be removing fan an belts this weekend as well. Thanks 

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3 hours ago, RPM said:

Just fyi, the 69 has a 3 bolt crank pulley, while the 70 and up is 4 bolt. 

Yes, this has a 4 bolt pulley. I have a new balancer so that is eliminated. Thanks 

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35 minutes ago, bigmal said:

I haven’t removed the wheel or tail shaft. I didn’t know you could run it with the tail shaft out. I thought it would loose transmission oil.

Can you run it without the yoke in? If so I will definitely try that. Will also remove the wheels as well.

as it seems dependent on engine rpm not wheel speed I didn’t think it would be rear of the transmission but it’s certainly worth eliminating everything that is easy before stripping the engine.

Will also be removing fan an belts this weekend as well. Thanks 

I would try and run it with the yoke in even if you have to take the uni joint out so you can eliminate the tail shaft . 

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Time to inspect that flexplate. You mentioned it was marked with felt pin which  probably means not original to the car and it was purchased at a bone yard and could have been marked wrong.

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I was under the impression everything but internal engine, the harmonic balancer, or the flex plate were eliminated.  On a side note, after you chase down the vibration it might be a good idea to check the charging system.  The ammeter in the video was dancing all over the place.  Might just be a gauge issue.  But worth checking.

I've never done this, but is it safe to unbolt the torque convertor from the flex plate, slide the torque convertor into the trans as far as it will go, then run the engine through the same RPM range.  This will eliminate the trans and drivetrain.  Just a thought, don't know how safe it is.  I guess it depends on how much clearance there will be between the flex plate and torque convertor.

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Not sure if he has ever changed the flex plate or not.  Barnett maybe right an internal engine problem and when it comes to engines he usually is.  That is a nasty vibration tho and one would think if an internal problem the engine would have come from together by now.

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1 hour ago, 1969_Mach1 said:

I was under the impression everything but internal engine, the harmonic balancer, or the flex plate were eliminated.  On a side note, after you chase down the vibration it might be a good idea to check the charging system.  The ammeter in the video was dancing all over the place.  Might just be a gauge issue.  But worth checking.

I've never done this, but is it safe to unbolt the torque convertor from the flex plate, slide the torque convertor into the trans as far as it will go, then run the engine through the same RPM range.  This will eliminate the trans and drivetrain.  Just a thought, don't know how safe it is.  I guess it depends on how much clearance there will be between the flex plate and torque convertor.

That is the first time I’ve noticed the ameter do that. I had almost completely flattened the battery starting as I hadn’t noticed the fuel shutoff was closed (part of the GPS disabling). Not that this should cause the flickering. I will add that to the list.

i am interested in the idea of unbolting the torque converter. Can’t see why tha wouldn’t work so interested in any comments on this before I damage something.

i have a busy weekend and not sure if I can get to the car. May have to take some more time off work. I’m not feeling well. Must be coming down with something 

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17 hours ago, 1969_Mach1 said:

 

I've never done this, but is it safe to unbolt the torque convertor from the flex plate, slide the torque convertor into the trans as far as it will go, then run the engine through the same RPM range.  This will eliminate the trans and drivetrain.  Just a thought, don't know how safe it is.  I guess it depends on how much clearance there will be between the flex plate and torque convertor.

Not sure about  all FMX's .  I have AOD and the converter will not slide back but about 1/4 inch and will not clear the studs. However a friend of mine has an FMX  that has bolts so in that case it would be doable but safest way would be as Barnett said  remove transmission with converter then bolt transmission (without converter) then mount  starter back. 

Bigmal 

If you have bolts in yours and try this just make sure the converter spins freely and the converter snout is away from the crankshaft.

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Well I have eliminated the front external of the engine. Removed all belts and the crankshaft pulley and it made no difference. I was going to look at unbolting the torque converter but ran out of time.

I'm now thinking I will leave it until the engine is out for heads and cam in October. Not much more to do to balance the engine while it is stripped that far.

I'll be very frustrated if it still vibrates then.

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When you have the rotating assembly balanced, they will also need the harmonic balancer and the flex plate.  If it were mine, I'd get a new flex plate and have rotating assembly balanced with a new flex plate.  If the old flex plate is the issue, you don't want unnecessary material added or removed during balancing because of it.

In the end, if balancing the rotating assembly fixes the issue, there's a good chance you won't know if it was internal or the flex plate.  Even if you have it balanced with the old flex plate.  So in my mind, after all that work, at least use a new flex plate and have it balanced with the new flex plate.

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55 minutes ago, 1969_Mach1 said:

When you have the rotating assembly balanced, they will also need the harmonic balancer and the flex plate.  If it were mine, I'd get a new flex plate and have rotating assembly balanced with a new flex plate.  If the old flex plate is the issue, you don't want unnecessary material added or removed during balancing because of it.

In the end, if balancing the rotating assembly fixes the issue, there's a good chance you won't know if it was internal or the flex plate.  Even if you have it balanced with the old flex plate.  So in my mind, after all that work, at least use a new flex plate and have it balanced with the new flex plate.

Thanks for that. I certainly will get a new flex plate and have it all balanced together. I don’t want to do it twice.

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I was just reading an article in Mustangs and Fords about Flex Plates and Dampeners:

http://www.mustangandfords.com/how-to/engine/1601-avoid-this-mistake-creating-a-balance-issue-with-the-wrong-flexplate-and-dampener/

As the balancer and flex plate have corresponding balance weights it would appear that they need to be correctly aligned.

Is it possible that the flex plate is installed in the wrong position so out of phase with the balancer?

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5 minutes ago, RPM said:

No Mal, not possible w/o a bfh. The 6 mounting bolt holes only align one way, so folks like us can't screw that up.

Bugger. Though I might be onto something. Thanks Bob.

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I went back and measure it. The dimensions are about 4 3/8 x 3/4 x 5/16 (110 x 20 x 8). It's a little hard top be accurate in the small space.

Is the counter weight normally on the engine side? I thought they were on the Transmission side. 

From the size of it I'm stating to think this is a 50oz plate????

It will make it a whole lot easier if it is.

 

Flex plate 2.jpg

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6 minutes ago, 1969_Mach1 said:

So far then, depending on the imbalance of the internal rotating assembly you either need to replace the flex plate with one that has a 28 oz. imbalance or you need a harmonic balancer with a 50 oz. imbalance.

Either way, its something that needs be addressed before you pull the engine. If it the flex plate, its a hell of a lot cheaper than having the internals balanced and then to find you still have a vibration.

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3 hours ago, unilec said:

Either way, its something that needs be addressed before you pull the engine. If it the flex plate, its a hell of a lot cheaper than having the internals balanced and then to find you still have a vibration.

The damper and flywheel or flexplate should always be balanced with the rest of the engine parts, this way if one or both of those parts is incorrect or not perfectly balanced, the balance shop will know right away so there will be no possibility of assembling the engine with mismatched parts.

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On ‎10‎/‎08‎/‎2018 at 6:11 AM, barnett468 said:

The damper and flywheel or flexplate should always be balanced with the rest of the engine parts, this way if one or both of those parts is incorrect or not perfectly balanced, the balance shop will know right away so there will be no possibility of assembling the engine with mismatched parts.

My guess is the motor was not balanced when rebuilt by the previous owner.

On a side note, I thought  all years of the 351W had a 28 oz. imbalance.  It was the 302 that made the change to 50 oz.  I vaguely recall reading a footnote about that in one of my Ford Racing catalogs.  Am I correct on that?  So did somebody install a 302 flex plate on that motor?

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1969_Mach1     All 351W that i have ever seen has 28 oz.  Not sure about all Cleveland's but I think they are too. I am not the most intelligent person in the world tho. 

Mal

I just measured one that i know came from a 351w because I took it from a 351w in a bronco that was running and driving, it is the same as the one RPM posted. If your measurements are anywhere close that might be a 50 oz seems a little long by 1" or so although the 5/16 and 3/4 dimension seem correct. i mentioned early on in this thread that when you said the plate was marked in felt pen it is possible it was miss marked. wouldn't be the first time. Marked with felt pen usually means it was purchased from a bone yard that was pulled from another vehicle. I have two 50 oz and one 28 oz if you need a pic. let me know.

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That's guys. I think there is enough doubt about the flex plate that I will replace it. I also think that it's not worth putting it back together and finding the vibration is still there so a full balance needs to be done.

This will also give me a chance to see just what's inside the engine. I will probably start in the next few weeks. I'll keep you posted of the progress.

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