vibration at 25-40 mph

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rich006 said:
OK, I get it now. I need some type of lock washer that is beefy enough, and I guess the mount itself can serve as the "flat washer." Loctite will make sure it stays in, and 1" bolts should be good if I don't add extra washers. And I'll check to see if the mount is actually OK.
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No the mount itself should not be asked to serve as the flat washer. The slots are much bigger than they need to be to just fit the bolts. They make it possible to move things around during the line-up process. If you expect the spring-washer to do double duty and act as a flatwasher;surprise! You will have fun making the point dig into the soft mount and cover both edges of the slot at the same time;remember,they are up there in a dark hole that you cannot even see the pointy spike. Furthermore it will be clamping on just two tiny crescent shaped strips of metal. When they pound out,the only think keeping the bolts from falling out, will be the loc-tite.And the mount will be free to move about, under the failed spring-washers.
With the factory parts loc-tite is not required.
Scaring up factory parts may not be possible,but taking a couple of thick,large-od/correct-id agriculture-equipment,washers, over to the bench-grinder to cut one/or both sides flat, shouldn't be a problem.
The factory stuff was a strip washer,like a short length of hard flat-iron with a hole punched in the center of it, cuz of the way the washer has to fit between the sides of the "tunnel", on it's way home.

Try to imagine why yours are missing now? There may be more than one answer.......
 
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AJ/FormS said:
No the mount itself should not be asked to serve as the flat washer. The slots are much bigger than they need to be to just fit the bolts. They make it possible to move things around during the line-up process.
Click to expand...

Ah, that makes sense. My photo from underneath does show that the oval opening in the mount is much bigger than the bolt. So that begs the question: how do you know when the transmission is placed correctly on the mount?
 
AJ/FormS said:
No the mount itself should not be asked to serve as the flat washer. The slots are much bigger than they need to be to just fit the bolts. They make it possible to move things around during the line-up process. If you expect the spring-washer to do double duty and act as a flatwasher;surprise! You will have fun making the point dig into the soft mount and cover both edges of the slot at the same time;remember,they are up there in a dark hole that you cannot even see the pointy spike. Furthermore it will be clamping on just two tiny crescent shaped strips of metal. When they pound out,the only think keeping the bolts from falling out, will be the loc-tite.And the mount will be free to move about, under the failed spring-washers.
With the factory parts loc-tite is not required.
Scaring up factory parts may not be possible,but taking a couple of thick,large-od/correct-id agriculture-equipment,washers, over to the bench-grinder to cut one/or both sides flat, shouldn't be a problem.
The factory stuff was a strip washer,like a short length of hard flat-iron with a hole punched in the center of it, cuz of the way the washer has to fit between the sides of the "tunnel", on it's way home.

Try to imagine why yours are missing now? There may be more than one answer.......
Click to expand...

That big lock washer will get down it that slot and do the exact same job AJ
Doesn't make a bit of difference what stops it from letting the bolt move.

Now that being said, I did use the big washers against the mount on this A500OD swap because I needed to modify those mount slots and there is even more of an open area under the washers now, but in that case I used the flat washers with a lock on top of it and blue Locktite on the bolt threads.
 
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rich006 said:
Ah, that makes sense. My photo from underneath does show that the oval opening in the mount is much bigger than the bolt. So that begs the question: how do you know when the transmission is placed correctly on the mount?
Click to expand...

I try to go with a combination of where things want to be and where they need to be.
Ideally there will be no pressure on the rubber of the mount except downward from the trans weight.
Gotta do what ya gotta do though too. :D

I spend a lot of hours doing this stuff and a few hours on here talking about it, so no offense to anyone, but I know what works and what doesn't.
 
I got the transmission securely mounted, and now the vibration is...worse and steady, no longer pulsing on/off. Is it possible the looseness of the tailshaft was partly masking an engine vibration? I do hear a noticeable ticking sound at about half engine rpm, and the video below shows that the transmission oscillation is at half the frequency of the driveshaft rotation (video is with trans in 3rd gear, so driveshaft rpm is same as engine rpm). I've read that a vibration at half engine rpm is likely caused by a poorly firing cylinder. If that's my problem, I think it's due to an overtight valve from the last time I adjusted them. Thoughts?

 
Is that tranny moving from side to side? I have never seen that before. And do I see the parking brake cable set-up also oscillating with the exhaust pipe?And the video is in real-time?
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With the pipe-motion assumed to be transferred from the engine,and thus the engine and transmission synchronized in their side to side oscillation, and with the transmission in drive, and thus the output shaft spinning at near crank speed, Ima guessing this motion starts inside the tranny;since you say the engine in neutral is dead smooth. Ima guessing this motion originates after the clutches. Since the rear bushing seems to be locating the driveshaft pretty well,Ima guessing the motion originates between the clutchpacks and the rear bushing. And that just leaves the trans output shaft,and whatever is rotating on or with it.
Why am I talking about the oscillation? Cuz I believe that may be the source of at least a major.part of your vibration. I know you said it was fine before the rear/shaft swap, but I can't speak to that.
Here's what I would do; With the engine idling and the trans in Drive,have a friend apply the brakes.Slide under there, and grab the transmission,at the rear bushing, and keep it there. Get the helper to release the brakes, and bring the speed up into the vibration range.As the driveshaft comes up to speed, ask him to kill the engine, and a second or so later, put the tranny into neutral.Let everything spin to a stop.Make a mental note of the vibrations.
Next remove the driveshaft and plug the tranny hole with a spare yoke, and repeat the test.Note the vibration and compare to the first test.
Best as I can figure, the tranny output shaft is bent,or something on it is very out of balance, and this test will prove it.
Or see TB's post below, for the short version.(This post edited after his post entered)
 
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Either that driveline is bent or there is a ujoint binding.
You can see it on the far right of the video that it is oscillating off center.

It might be a PIA but I'll bet you 10 bucks if you took the driveline off and removed the yoke then ran it with the yoke only in it all that crap would be gone.
It sure would answer the question wouldn't it?

Better than wondering about it for days. :D
 
It's iPhone slo-mo video. The beginning and end are real-time, but the middle is at 1/8 speed. Notice that the transmission makes one full left-right cycle while the driveshaft rotates twice. That means the transmission vibrates at half the engine rpm.

I'll update again after I readjust the valve lash. Didn't have time over the weekend...

By the way, the driveshaft was shortened and balanced, with new u-joints, at a shop that only does driveshafts. I certainly hope they did it right.
 
rich006 said:
It's iPhone slo-mo video. The beginning and end are real-time, but the middle is at 1/8 speed. Notice that the transmission makes one full left-right cycle while the driveshaft rotates twice. That means the transmission vibrates at half the engine rpm.

I'll update again after I readjust the valve lash. Didn't have time over the weekend...

By the way, the driveshaft was shortened and balanced, with new u-joints, at a shop that only does driveshafts. I certainly hope they did it right.
Click to expand...

The problem I have is that there isn't an engine miss in the world that makes a trans jump around like that.
Something about that driveline is AFU.
 
watching this thread closely as my 73 dart has this pulsing vibration at over 40 mph at steady speed less on acceleration, that wow wow wow at cruising is annoying lol
 
mikec said:
watching this thread closely as my 73 dart has this pulsing vibration at over 40 mph at steady speed less on acceleration, that wow wow wow at cruising is annoying lol
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Before you go crazy,swap a different set of wheels onto the back. Sometimes(many times) that type of sound is a tire issue exciting the natural body rhythm.Make sure both rear tires have near-matching roll-outs, so the differential is not also part of the issue.
 
Here's another video with the driveshaft removed (with rear end jacked up to keep the yoke from sliding out). I forgot to make this one slo-mo, but you can still see the transmission wagging back and forth, and also the exhaust pipe. The seat-feel of the vibration was the same with the driveshaft removed. Next step: reset valve lash.
 
That's not likely to be a lash issue, but I guess you gotta start somewhere.
I would put a dial indicator on the smooth part of the slipyoke and rotate the output shaft a few revolutions. It will be tricky, for sure;but that's where I'd start.
Actually it can't be a lash issue.There is no mechanical connection between the engine and the output shaft.There is only a fluid connection inside the TC. So any minor cylinder pressure fluctuation caused by a lash issue,would be damped out by the ATF.
That's my story and I'm sticking to it.......
Plus an engine vibration would not send the tail wagging in consistantly the same direction. The tailshaft motion in your video clearly shows the oscillation to be in a transverse direction.This can only be caused by the output shaft or something fixed to it.At least that is my belief,at this moment.
 
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How about torque converter unbalace or internally damaged converter ?
 
Again, since the TC is bolted to the crank, I can't see it causing an imbalance in exactly one direction at the end of the output shaft. Every time you change the throttle position,the fluid coupling in the TC will re-couple in a new direction, and so the tailshaft oscillation would move to a new direction.
An out of balance,or damaged TC will shake the engine, which will shake the tranny alright, but I just cannot imagine it causing a consistent one-direction-only tailshaft oscillation.
Now there is every possibility that I'm wrong, and I'm really anxious to see the solution to this, cuz this is the reason I'm into this trade;learning new stuff.
 
great thread, still watching for info, great vids of driveline thanks to op for posting and all the comments. really helps everyone
 
I should mention that the vibration is now happening both in gear and in neutral/Park. So I don't see how the tailshaft could be the main problem. I wanted to do some more troubleshooting this weekend but home projects got in the way. More to follow...
 
Yesterday I found a disconnected vacuum line. Since I plugged it back in, the vibration is not noticeable. You can still see the exhaust pipe shaking if you look under the car, but you can hardly feel anything.
 
AJ/FormS said:
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Plus an engine vibration would not send the tail wagging in consistantly the same direction. The tailshaft motion in your video clearly shows the oscillation to be in a transverse direction.This can only be caused by the output shaft or something fixed to it.At least that is my belief,at this moment.
Click to expand...

AJ/FormS said:
Now there is every possibility that I'm wrong, and I'm really anxious to see the solution to this, cuz this is the reason I'm into this trade;learning new stuff.
Click to expand...

Ok, color me red! thx for the lesson.
 
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