Vibration Is Back

[pastortom1]

I'm at wits end...........

If I told you the number of old Mopars I've worked on that have vibration problems you'd think I'm nuts (probably do anyway.....oh well..)........

The latest is a 360/727 combo that is making me crazy.

When I got the car in the shop it had u-joint problems......very obvious......practically falling apart. The driveshaft had a dent too, so I had a new shaft built and balanced and new joints put on. It felt pretty good, BUT it still had a harmonic vibration that felt like it was somewhere from the tranny back.

The vibration worsened until the tailshaft bushing sounded like marbles from all the flopping around in there...........I had the tail freshened up with a new bushing.....they said the bearing felt really good, so they didn't change it.

When I got it back, no more noise and just a very little harmonic to speak of at around 45 mph at a level pedal. Over the next 60 to 70 miles of local driving (at or under 40 mph) the vibration came back with a vengeance.....now I can hear the bushing beginning to "rattle" again at the level spot (cruise on the pedal), and to be frank, I'm afraid to drive the thing now.............WE'RE TALKING LESS THAN 80 MILES TOTAL SINCE THE NEW BUSHING.............!!!!!!!!!!!!!!

You guys have pointed out that the 360's were all externally balanced......OK.......I need to visually inspect the torque converter for counterweights I guess.......that's a given........BUT, I had a Cuda 340/727 with vibration from a mismatched converter, and it NEVER messed up the tailshaft bushing or the u-joints.........ever.

My driveline angle seems dead on........I have 1-1/4" clearance from the end of the tailshaft to the yoke of the driveshaft....seems right on.....the driveshaft was professionally built and balanced......u-joints now have about 300 miles on them and seem tight.......but there is STILL a little slop when you force that driveshaft back and forth at the tail shaft housing.....not much, but it's there.........Is a little bit normal? I don't honestly remember any from my drag racing days............

My planetary's are a little "whiney" but always have been.......I was told it was a "built" 727, and it does shift like a bear......really nice......BUT the gears are a bit loud, but nothing I haven't heard before in a beefed up trans............Is there something I'm missing?????????

There is something out of balance in there that is knocking my tailshaft bushing to hades, killing my u-joints, and just plain driving me nuts...........

What else should I do other than be sure that the converter is not mismatched? (be sure it's a neutral, I mean)..............?????

 

[RedFish]

The tailshaft bushing is somewhat of an intermediate part in the grand scheme of things.Its just a surface for the yoke to turn on/in.
The tail shaft needs to run straight and true in its bearings. The splines on the shaft and the splines inside the yoke center the yoke in the bushing.
Bad bearings or severly worn splines will take that bushing out repeatedly.

 

[lhearold]

Do you get the harmonics with the car in park and the engine at the RPM that it runs at 45 MPH? If not then its in the driveline, not engine. You will get engine vibs with the car standing still.

What is the tranny out of? I had a problem a few years ago with a long tailshaft tranny vibrating. It was out of a mid 80s truck and had a counter weight hanging onto the tailshaft. Naturally I removed it when I installed it into the car and got a harmonic vibration at around 40 MPH up thru about 70 MPH. Put it back on and problem went away.

Since yours is eating the bushings, check for runout on the output shaft. If you aren't sure of the history of the tranny, it may have been in a bad accident and bent the shaft. Not a common occurance but I have seen it a couple of times. Usually busts the tailshast housing though. But that doesn't mean someone didn't put it together with a lot of unknown parts. If you have one, try changing out the whole tailshaft and housing and see if the problem goes away.

Larry

 

[pastortom1]

The tailshaft bushing is somewhat of an intermediate part in the grand scheme of things.Its just a surface for the yoke to turn on/in.
The tail shaft needs to run straight and true in its bearings. The splines on the shaft and the splines inside the yoke center the yoke in the bushing.
Bad bearings or severly worn splines will take that bushing out repeatedly.

..........and it seems to me that the bearing almost HAD to have had some problems if the bushing was as bad as it was.......BUT, the shop said the bearing was like "new".............I have my doubts at this point.

There is just one bearing in there for the tailshaft....is this correct? One bearing and one bushing?........ What are the chances of the actual tailshaft being "out of balance" due to a micronic "twist" from drag racing??

Is it possible that there is an ever-so-slight twist in it from torque that has thrown it out of wack??

 

[lhearold]

It could be mis-aligned which would cause the shaft to put a strain on the bearing and also may be enough to cause runout. Have you checked for runout where the yoke slides over the splines? As Redfish said, it could be severely worn splines. Any looseness between the yoke and splines?

 

[pastortom1]

I'm gonna have to check this myself instead of trusting it to someone else I guess..........happens all the time...........

For that bushing to be wearing so fast, there almost HAS to be something wrong on that shaft OR the splines, either on the tailshaft or the yoke.......

When you have a driveshaft built, you tend to assume that they would check the inner splines to see if all was well........and the same should go for a tranny pro when they take out your tailshaft........Obviously someone has missed something................THIS THING JUST AIN'T RIGHT.............Terrible vibration................

...........and to a previous question, NO it doesn't vibrate in neutral........that's the first thing I checked when I bought the car......been there done that.......I've had a couple of mismatched balancers in my day too, and to be frank, I'm REALLY sick of this type of problem with these cars.

Vibrations take all the enjoyment out of the ride. Any of you'se guys have a nicely rebuilt complete tail housing out there just sittin' around?? Give me a shout. :-D

 

[JR]

Do you have one of these on the end of your tailshaft? it is a counter balance that some of the 904s and 727s had. When I put the 727 behind the 360 in my 73 Scamp I had one hell of a vibration over 30mph I put one of these big chunks of metal on it and it went away. The 904 and 727s are not the same so measure the 2 bolt holes on the very end of your tailshaft and find one that fits. All I have are 2 904 ones other wise I would send you one.

 

[pastortom1]

Just what exactly am I looking at here in the picture?............Does it mount on the outside of the end of the housing? Maybe my cold pills are messin' with me..............:happy10:

 

[JR]

It mounts on the very end of the tail housing. there is a flat area with 2 threaded holes for it. give me a min and I will go get you a better pic. BRB

 

[JR]

If you don't have one it may be worth a try. they were on cars, trucks, motorhomes ect. Just look under if it has one 2 bolts and get out of the way cause they are heavy!

Here ya go.

 

[pastortom1]

I thought that's where it went, but didn't think it was that big!!!!!!

It almost seems that that's where the problem must be...right in that area.....that section of the housing just hangs there with little support except for the thin aluminum shell........what you're showing makes some sense.......

But WOW that's a monster..........!!!! I have never seen one to be honest.

There are a couple of pretty good yards here I could call.......I think I'll send 'em that last pic you posted and see if maybe they have something......

It's worth a try.................Thanks for the heads up!!