vibration problem

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trudysduster

trudysduster

FABO Gold Member
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I have a 76 Duster I bought 10 years ago and it had a 225/904 combo with a junk rearend. I built a 440 and put a 727 tranny in it and had Moser Engineering fix up a 8.75 rearend for it. I put a set of 3:55 gears andit all seemed ok. I decided to restore it and every nut and bolt came out of the car, dipped repainted the whole ball of wax. Put the same engine back in, same tranny and same rearend. I decided to go with a 4:10 gear. got the car back together,painted , and now I have a vibration that seems to be in the driveline. I thought it may be u-joints so I took the driveshaft to the driveline place and told them to replace the u-joints and balance the shaft. He told me the driveshaft was too short by looking at where the boot rubbed on the shaft. Measured it and lengthened it 3 inches. Put it back in and still a vibration. Thought something may be in the rears so I switched rears and put a 3:91 punkin in it. Still vibrates. Could something have happened in the tailshaft by running a too short driveshaft or in the tranny itself. The tranny runs perfect and shifts so smooth. Am I missing something. About to pull what little bit of hair I have left out. Any help will be appreciated. Maybe someone else has had this. Bill
 
You have my sympathy. But I'm no help. No hair either. I’ve been there with a hot 340 72 Challenger. Finally sold the car, but not because of the “mystery” vibration. (But only above a certain speed) Tried a lot of things. Never fixed it. Could have even been tires. I know there are some things inside the vodoo science transmission that can cause vibrations.
I hope someone with drive train expertise can give you a hint of what to check.
My questions would be things like does it only vibrate under a load? Does it help to go to coast? You know that Chrysler put “vibration dampeners” on the tail shaft of transmissions. Most people take them off and they are missing.
NOT saying they are necessary. I don’t have enough experience to say.
Just saying. They were there for SOME reason.
 
I think the first thing you need to do is determine if it vibrates when sitting still and in park or neutral. If so it's probably in the converter/flexplate/engine.Furyus2
 
If the vibration has the frequency of a heard of pissed off bumble bees, it is drive line related. If you can feel it more in the floor, seats and steering wheel, it will be tire and wheel related. I would nail down which it is FIRST, or you will be forever chasing your tail. I'll tell you something you can do YOURSELF that will cost very little and is very easy to do.

Get 4 steel hose clamps large enough to clamp around the drive shaft. Clamp all of them on with the screw clamps lined up together. Drive the car. Note whether the vibration is better or worse. Move the clamps 90* at the time until the vibration improves. Then, move the clamps 45* until the vibration improves even more. I think you see where I'm going. When you get the vibration gone, you can get a drive shaft weight yourself and tack weld it on the drive shaft.
 
no problem sitting still or neutral. replaced the flexplate when I installed the convertor. The bushing in tailshaft sounds like it might be bad. The vibration feels like it is driveline related but it has been balanced.I feel it more around 45-50 mph and I feel it in the floor and some in the wheel.feel it most when I accellerate and let off the gas.It feels somewhat like a grind instead of a bounce type vibration. I am puzzled.
 
" have a 76 Duster I bought 10 years ago and it had a 225/904 combo with a junk rearend. I built a 440 and put a 727 tranny in it and had Moser Engineering fix up a 8.75 rearend for it."

When Moser did your rear,did they build the whole rear including the spring perches? Could be they were installed wrong. You can buy wedge shaped shims from Summit and put them under the perches. Thick part to the rear points the pinion down.If it gets worse, try thick part to the front. These vibration issues are a process of elimination.
 
Just a thought- are the centerlines of front and rear u-joints in line? If the shaft is twisted even a little, it can bind up the u-joints. This could give you the "grinding" and shudder. My .02
 
If the shaft was 3" short, id be suspect you killed the bushing, and the slip yoke should have some signs of the bushing is f u.

Then after you take a look at the play on the bushing then get into very detailed specifics on the vibration, starts, gets worse, ends at, or worse at. all of that, remember ain't none of us sitting in the car. . .
 
I'll add my name to the list of many with this problem. Mine gets into a harmonic at about 67 mph and the pulsation then increases with speed. I don't want to push it past 75 mph to see if goes away at higher speed. Does nayone know how much radial play there should be in the tail shaft of the A727? Since O'reilly apparently sold me the wrong rear seal (they're battin' about .150 overall), I have to pull the drive line again anyway so I'd like to check it.
 
If you've eliminated all the common causes......u-joints, damaged driveshaft, engine/trans mounts, etc.....check the pinion angle of the driveshaft and the exhaust hangers/mounting. Sometimes if the exhaust is mounted too tightly, it will drone and act like a mechanical vibration.
 
............what did u use 4 a flexplate and converter combo........were they in b4 the resto or when everything went back in,,,,,,,,,,,,,,,kim........
 
75Sport said:
There's a bushing in the tailshaft of the TF. It's probably shot and causing your problem.
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I had a bad vibration in my Dart. Tranny needed building so I pulled it and sent it to the trans guy. Got it back and was going to test drive it and check pinion and other things to get rid of vibration but when I drove it all the vibration was gone. It was what 75sport said. Bushings were shot in trans.
 
I finally had a chance to tear into my tranny. Mine is a TF A904 and has a ball bearing (National p/n 206-LOE) in the extension housing that is about 1/2 way along the output shaft. This means there's lots of cantilevered output shaft after the bearing. Doesn't seem like a good idea to me, but that's the way they are. That ball bearing on mine was totally shot. The outer race could almost fall off the inner race when I took it out. The new bearing is like night and day difference. The car is smooth at highway speeds now. That's one more I can scratch off my list.
 
If the torque converter sat for ten years contaminants in it can settle to one spot and throw the balance off.
 
im chasing a similar demon in my 74 duster; 360 with 727 and 8.75. it vibes about 40-50, while in neutral or drive, the humming bee.. hmmm---hmmmm---hmmm.

did u-joints and im checking all the basics (wheels and tires, ect...) like fury said, its a process of elimination just like all trouble shooting. Im in the middle of it myself as are many others it seems.

It sounds to me however, that you are narrowing it down pretty well. you changed out the rear end, balanced the d-shaft with new joints...it appears that it is most likely driveline at this point, quite likely that tail shaft bearing took a good beating.

according to your second post... if it vibes in neutral while rolling down the road, logic would state it should be from the tranny back...you swapped out just about everything from the rear end to the tranny... so i'd again point to that tail shaft bearing...
...BUT...
I didnt see a post saying you tried tossing a different set of wheels on there yet...although unlikely, a bad tire can cause that. I chased down a vibration in my mothers beemer for months; it had a classic bad wheel bearing feel, it ended up being a crap tire. put new ones on and it was gone forever.
 
MoPowAR said:
im chasing a similar demon in my 74 duster; 360 with 727 and 8.75. it vibes about 40-50, while in neutral or drive, the humming bee.. hmmm---hmmmm---hmmm.


so am i,just put in a 318/727 in my 73 duster. a matching set out of a 67 coronet. took 4 inches out of the driveshaft,professionally built and balanced,all new u joints. tires are all balanced. exhaust pipes are mounted with hangars. only vibrates moving at and above 55-60 mph.i havent pushed it past 80 to see if goes away.did not have a vibration before the 225 swap out. this is the original 727 to the 318 so there are no converter or balancer issues, and it is just exactly like you describe hmmm....hmmmmmm....hmmmmm... lol post up if you figure it out !
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.................OK guys.........i fixed a 74 duster awhile ago.........as i've did and so have others with aftermarket wheels that required the weights come off the rear drums so they fit flat to the hub and not have a problem with wobbling..........the guy tried alot of things, nothing helped it.........put on a new set of drums with the weights on them, 1 problem solved as now he needs different wheels as they wont sit flat with the weights on.......not a bit of vibration with the rallye wheels.......he's happy the vibe is fixed, but totally pissed at the tire shop that sold him rims and tires[over $1000.00] worth.....they said the wheels were wobbling, so they removed the weights and threw them away.....ofcourse he was chasing this vibe 4 a few years, so they wont do anything 4 him......it will cost him $100.00 per each rear wheel 2 have them milled out to clear the weights................kim...............
 
oldkimmer said:
.................OK guys.........i fixed a 74 duster awhile ago.........as i've did and so have others with aftermarket wheels that required the weights come off the rear drums so they fit flat to the hub and not have a problem with wobbling..........the guy tried alot of things, nothing helped it.........put on a new set of drums with the weights on them, 1 problem solved as now he needs different wheels as they wont sit flat with the weights on.......not a bit of vibration with the rallye wheels.......he's happy the vibe is fixed, but totally pissed at the tire shop that sold him rims and tires[over $1000.00] worth.....they said the wheels were wobbling, so they removed the weights and threw them away.....ofcourse he was chasing this vibe 4 a few years, so they wont do anything 4 him......it will cost him $100.00 per each rear wheel 2 have them milled out to clear the weights................kim...............
Click to expand...


as soon as i read this i ran down stairs to check out the drums haha. the rims are ol cragars and flare away from the drums, so no one should have taken any weights off, BUT....

just an fyi, last week i ran to autozone 2 miles away to grab stuff for an oil change, kept the car under 45, couldnt really feel or hear the vibration, i just got the car runnin right and back on the road that day mind you and had just started trying to chase down the vibration... so i was comin back and noticed the vibe was really bad, getting progressively worse, coming from the rear left. so i slowed down and started to pull over.

as i did the rear left wheel decided it had enough rockin and that it was time to start rollin...right off the studs and down the road!!! but not before showering the hood of a SQUAD car with all 5 lugs and washers! the car plopped down on the left rear trailing arm as i slowed to a stop!

the cop was nice as all hell, put up some traffic cones and helped me find the lugs while i waited for my buddy to bring a floor jack to boot! and of course he showed me some pics of his ols 442. it was real low speed (luckily) so no damage, just ground some paint off the bottom of that arm.

anyway, the right rear drum has a weight on it, all lugs stayed tight... the left rear drum however, has no weight on it, and it rattled loose all 5 lugs! First thing this weekend its rollin over to a shop to balance all four wheels and that damn brake drum too... I'll let y'all know if its another case of no drum weights...
 
so i havent been able to find a shop who was willing to "balance" or even look at my brake drums... i havent been able to find a reman pair either because i have no idea where the 8.75 rear end in my duster came from...

I did however hear from one guy that a bent axel would throw out the symptoms alot are chasing here... now if thats the case, what kind of torque would it take to bend an axel in a rear end that big???
 
ask for drums for a mid 70's dart .. they are almost all the same.. just take one along with you to compare
 
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