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Discussion Starter #1
69 Conti 4dr 460, stock 2.80 open diff, pretty sure lincoln only.

Getting a clanking banging noise, rhythmic. Sometimes sound, GENERALLY on deceleration off throttle coasting down hill. Speed seems to affect it as far as speed of the bang. When noise starts if it accelerated even slightly goes away. but i have had it happen on the flat just cruise control on. I have had it at high speeds and 20mph. it is much louder when riding in back seat. I cant make it happen at will. Some drives it wont happen, some drives it happens often, even replicating same route and speeds. i dont seem to have any control over the noise except accelerating to go away.

I have tried putting it in 2nd and going up and down hills to see if i can force the sound, it never happened during that test. I have NOT been fast enough on the draw to slide into neutral and roll while it happens to see if that changes it.

I have put it up in air on jack stands and spent a long time looking and shaking bits for looseness but nothing I could find. the rear end I believe to be original and untouched, so 51years 103xxx miles. Pulled the fill plug and it was full. Drive shaft was professionally rebuilt (new U joints all around) and balanced. But that was 12 years ago but only 15xxx miles. These are (I think and i might have the term wrong) double cardone joints on each end? I think meaning move pivot points than usual for smoother running.

i suppose something else could be rattling but it all seems rigid and not contacting each other. My thinking, though i dont want to influence your thinking, maybe rear center? lash issue? wear issue? coming on the coast side of ring and binding? accelerate to get on the thrust side goes away? but if doing that shouldn't I be able to make that happen pretty easy? and regardless of gear the trans is in? and i was trying to load and unload the diff in one of my tests and it never did it? Like if diff related shouldnt it be an all the time thing not a come and go thing? even if it requires specific circumstances, if i do those things it should happen, but so far not the case.

open to suggestions? Trying to find a place to bring it to local, hard to find anyone I trust and dont often farm stuff out. but im dumbfounded.
 

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Sounds like your u joints. Just takes a little time to pull the shaft and check them.
On all my Mk 111's if they sit a while without use the u joints seem to get a set in them and wear.
I got to whenever I let my cars sit a while I would go and lube everything and have not had any more problems.
103,000 miles on the 69 Lincoln is just getting broke in, 2 of mine had over 200,000 miles on them and ran fine when I sold them.
good luck
Greg
 

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Discussion Starter #3
Thank you for the reply, no issues pulling drive shaft, but what am I checking for? Just smoothness of pivot?

The car does sit a lot and actually was mostly sitting the last 2 years as it was being painted and then interior was out. Now that's done and I've started driving it proper again.

I don't recall if they are greaseable with zerks either. If so maybe that's first step
 

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I don't remember if they had the greese zerts or not but on every car I build I add them. The original grease less were supposed to be a lifetime useable but I found out that they last about 40,000 miles and need to be replaced.
When you get the shaft out you want to check for any slack or play in the u joints. There should be none or very little [one to two thousands]. You hold the shaft and twist on the u joints and see if there is any play in them.
If they are good to go then jack the rear wheels off the ground and have a helper turn one of them back and forth and listed for any grinding or other noise in the rear. It could have to much back lash in the pinon. You should be able to turn the yoke about 1/8 inch before the yoke turns when turning the wheel.
Don't forget the jack stands.
Hope I explained this where you could understand it as I am not to good giving directions.
Greg
 

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Discussion Starter #6
today i looked at the driveshaft again. I pulled the DS out so i could get a good feel for the the U joints, maybe some tight spots?? but nothing glaring, no big slop. but I know all 4 joints were replaced 12 years ago, i suppose something like 15000 miles ago and have never been greased. I greased all 4 pushing out all old grease until new came out. I went for a drive and at first all things were quiet. then during my ride i hear it slightly and only for a moment 3 or 4 times. so much better than my last drive.

So working theory is the grease quieted it down for a bit but will likely come back with more driving? I have ordered up 4 new joints and will replace them. Seems like a reasonable thing to do right?

also while DS was out I took a video of the pinion/wheel. trying to demonstrate how much play is there. Please look over this video and watch the yoke movement relative to the tire to see how much slop there is. Does this seem excessive?? maybe the video cant show it well enough.

 

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Rotational slop is normal backlash,up and down,side to side,no good. Pinion bearing will need attention if that is the case.
 

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I think you have found most of your problem with the u joints. I really couldn't tell from your video as a lot of that is by feel but thermod is right about slop.
Drive it and see how it goes and if you have replace the pinion bearing.
Greg
 

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My experience with U-joints, is by the time you realize you need to grease them some damage has already been done. I'd replace them. Less than $50 if you can do it yourself usually. I've had 3 piece driveshafts rebuilt for $150 in an F250 superduty.
 

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Discussion Starter #13
Also found a broken trans mount and a so so other one. Replaced. Drove only 25 miles no noise.agreed u joints if grease helped damage done. So not done with this yet but finding multi factors
 
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