Driveline Vibration

[rheltzel]

This thread is related to: https://www.fordbarn.com/forum/showth...veline+ticking

Weighing all the good advice I got on this forum, I went ahead and replaced the worn pin referenced in the above thread with a No. 8 hardened bolt and nut. This repair occurred as I was also installing a new engine. I also replaced the bearing bushing (although not the bearing) at the front of the torque tube as it seemed there was a lot of sideways slop in the drive shaft.

First drive with the new engine and repaired drive pin indicated a roughness under throttle at 50-55mph which was never present with old engine and drive pin. At first, I attributed the rough spot to a very tight engine, although there was no rough spot when revving the engine in neutral and listening with an engine stethoscope did not produce a similar roughness or any abnormal engine noises. As the engine wore in, it became obvious that the roughness wasn't the engine, but somewhere in the driveline.

The next suspect was the rear end. Putting the car on jacks and working the rear end indicated a great deal of slack and ratcheting differential action, suggesting the rear end was in need of repair. I located and purchased a newly rebuilt rear end from a fellow Ford Barner, and completed the installation a few days ago. During the change-over, I noticed the pinion splines on the old rear end were completely shot (I missed that when the pin was fixed). The No 8 bolt with less than 2,000 miles on it already showed excessive wear on the shank, suggesting it was taking the torque load caused by the worn splines. There was no evidence of wear on the bolt head or nut.

There is no slack in the new rear end and the differential action is smooth as you would expect. The rear end seems perfect. The new bushing installed previously showed no abnormal wear patterns, in fact, no wear at all.

When first driven and everything is cool, there is no vibration, but as the car warms up, the vibration, is still there, in other words, heat has some effect. And it's getting much worse -- it first shows up at about 30 mph and progressively gets worse until about 60mph and then seems to fade a little.

I'm confident it's not the rear end, the rear transmission bearing, nor the u-joint, as nothing was done to them during the work described and the noise was not present before the work was started. I'm also confident it's not a wheel bearing, as again, they weren't touched during the work. I've put two different distributors on the engine and swapped out the condenser with no effect, so I don't think it's retarded engine timing causing the engine to run rough. It seems to run perfectly.

Sorry for the length of this, but I wanted to set the stage by fully describing the circumstances and symptoms.

Now my question: other than the bushing that was replaced, what could possibly be the cause of the vibration? I'm stumped, as I can think of no other cause.

My theory is the clearance between the bushing and bearing is too tight and they are partially seizing when heat builds up between them. Can anyone think of something I'm missing here, before I tear into it a third time?

[Ken/Alabama]

What year car.If yours has the bearing inside the torque tube it could be going bad.

[rheltzel]

It is a '35 with the tube type shaft. No center bearing.

[Ken/Alabama]

Are you positive about the u-joint??

[rheltzel]

No, I'm not. There's no indication of wear. More to the point, there was no vibration before the engine exchange work began.

[Binx]

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To isolate it to driveline/trans/differential, run it up to the 30-60 mph speed, coast with the clutch in then coast in neutral with clutch out and see if you still have vibration.

My gut feeling is the fan/generator since the problem begins after warm-up. Also, what does your "noise" sound like?

Lonnie

[swedishsteel]

I have had a similar vibration, only on a modern vehicle with disc brakes--long story short, it took me awhile to figure it out but one of the rear calipers was hanging up ever so slightly, just enough to heat up the brake pad, and the hotter the pad got, the more the vibration. You said the vibration is related to heat. Drive until you feel the vibration, stop and get out and feel if one of your brake drums is hot. Just an idea. Good luck. Rod

[rheltzel]

Originally Posted by Binx

To isolate it to driveline/trans/differential, run it up to the 30-60 mph speed, coast with the clutch in then coast in neutral with clutch out and see if you still have vibration.

My gut feeling is the fan/generator since the problem begins after warm-up. Also, what does your "noise" sound like?

Lonnie

Lonnie, the vibration only happens under throttle. It sounds like a growling noise. I'd think it was either the rear end or the u-joint if I hadn't just replaced the rear end and knew that there was no noise/vibration with the same u-joint before work began. Literally the only thing that's changed is the installation of the drive shaft bushing. That's why I think it's the cause, but wanted everyone's thoughts before I tear the car apart for a third time. I was hoping against hope that someone would say "it's caused by ____" and I'd say "of course...hadn't thought of that".

[rheltzel]

Originally Posted by swedishsteel

I have had a similar vibration, only on a modern vehicle with disc brakes--long story short, it took me awhile to figure it out but one of the rear calipers was hanging up ever so slightly, just enough to heat up the brake pad, and the hotter the pad got, the more the vibration. You said the vibration is related to heat. Drive until you feel the vibration, stop and get out and feel if one of your brake drums is hot. Just an idea. Good luck. Rod

Rod,

Tried that. Nope...no indication it's a dragging drum (car has '46-'48 drums/brakes).

[rheltzel]

P.S. Lonnie,

Same generator from old engine. No change there.

[hydropower]

Did you change the female end of spline at differential?

[scooder]

When you go back in there, change the grade 8 hardened bolt for 5, believe it or not, in this application the hard bolt is more likely to snap than a soft one. The soft one has the necessary amount of give to last in this setup.
Its not there to transmit torque, it's there to stop the drive shaft moving along the spines, backwards and forwards if you will.
This is from experience.
And as above, you said the pinion splines were badly worn, what about the female end on the drive shaft?
Martin.

[Mart]

I am backing up my buddy Martin on this one. Use soft material for the pin. I used an allen bolt and it snapped.

I would like to see where "following advice" you were told to use a grade 8 bolt, the only references I have seen have been to use a soft grade of material.

Mart.

[JWL]

I fully agree. Use a more malleable bolt or pin. When I am dealing with worn splines I "neck down" the pin in the lathe so the splines make contact before the bolt or pin begins bending. There are only so many cycles between a one piece and a 2 piece pin.

Now to your vibration problem--my first thought was U-joint but I am now wondering if the driveshaft is the problem? Perhaps by replacing(tightening) the running area of the driveshaft it is transferring oscillations into the running gear that were previously being harmlessly dissipated by the self-centering u-joint. Put the shaft in a lathe and do some checking with dial indicator. Yes, I know that sounds easy but requires mucho work.

Good Luck,
JWL

[D. Jones]

Rheltzel, when you said the noise started when you changed out the rearend I started wondering if you changed the whole differential or just the gear set. If you changed the whole differential as a unit did you check the spring perches and the bolts, shackles ect? I am wondering if the differential is torquing to a different angle and causing binding of the drive shaft.

Again, just my $0.02 worth.

[V8COOPMAN]

Originally Posted by D. Jones

I am wondering if the differential is torquing to a different angle and causing binding of the drive shaft.

Again, just my $0.02 worth.

That type of situation just doesn't come into play with a torque tube design. DD