For those that have rebuilt their CV/Double Cardan joint thing...VIBRATION ISSUE

[bmc69]

Also, I have read several threads about the ears of the slip shaft being "in phase" with the forward side. Many have said that this isn't necessary with the CV joint? Is this wrong? If it is wrong, then I very well could have it messed up. I did, just for giggles, line up the back end up the way you are supposed to with the old non-cv joint shafts. But, I could be 180* off.

Technically, it should not matter what the "phasing" is between the double cardan (a "CV" setup) and the pinion joint; that said, I've had a couple driveshafts that had a pesky vibration at certain speeds and it did change for better and worse by playing around with the phasing. Hit or miss though.....

 

[Devin]

Ok, so if I find some time (which I probably won't because I am constantly working on that stupid F350 since I bought it), I will play with the phasing on the rear slip shaft.

Does it matter if the h-block is "out-of-phase"? I marked it before I removed it, so I put it back on the way that it was, but should I attempt to flip that piece 180* also if changing the phase at the rear side does nothing?

 

[bmc69]

Ok, so if I find some time (which I probably won't because I am constantly working on that stupid F350 since I bought it), I will play with the phasing on the rear slip shaft.

Does it matter if the h-block is "out-of-phase"? I marked it before I removed it, so I put it back on the way that it was, but should I attempt to flip that piece 180* also if changing the phase at the rear side does nothing?

The only reason you mark something like the H-block and adjacent shaft for "phase" is to keep a balanced shaft in the orientation in which it was balanced (assuming it was). Has nothing to do with the u-joint phasing as related to Hooke's formulas and the cancellation of the variation in angular rotation; there is nothing you can do to screw that up when you assemble the double-cardan joint. It should always look like this when you have finished the job:

 

[DirtDonk]

Shouldn't matter whether the CV is one way or the other, so flipping 180 should not be needed.
However, the shaft sections should still be in-phase with each other.

If you imagine the driveshaft as a single-cardan type, line up the ears of each yoke with each other and you should be good.
In other words, it should look like this:
http://www.wildhorses4x4.com/product/Extreme_Duty_Driveshaft_Front

Paul

 

[bmc69]

.
However, the shaft sections should still be in-phase with each other.

Why? ...?:?

I line them up when I build 'em but from an engineering standpoint there is no velocity variation that needs cancelling in that shaft configuration; that is why the pinion u-joint angle needs to be very close to zero so it does not create one that is not compensated for elsewhere.

 

[DirtDonk]

I hear what you're saying, and it's very possible you're right. But they're all built that way. They're all shipped that way from the factory and supplied that way by any number of builders. So I'm just thinking that to rule out any variation that might arise from whatever other dynamic circumstances that exist here (the angles we're working with? something else?) that we should put shafts back together the way they came apart.

I saw what you said in post #21, that it shouldn't matter, and can't refute it. But you also said that playing around with the phasing has even helped you in the past. So what's the issue with the OP trying the same things you have? At the very least it will help to rule out phasing as an issue in his case?
In trying to track down a vibration I thought it would be a good idea to make sure it was the same orientation as it was built. If only to rule it out as a potential issue.

Paul

 

[bmc69]

I saw what you said in post #21, that it shouldn't matter, and can't refute it. But you also said that playing around with the phasing has even helped you in the past. So what's the issue with the OP trying the same things you have? At the very least it will help to rule out phasing as an issue in his case?

That's why I suggested that he play with the phasing of the rear segment...because for whatever reasons I've actually seen it make a vibration go away. Most likely a balance issue..but whatever works.

For the record, my shop builds custom driveshafts. I've built some that have to transmit over 4000 shaft HP (marine applications..but still cardan shafts). And we're a Rockford Constant Velocity OEM shop and dealer...have been for about 14 years now. (Hint: "R C V".....;D). Some of my trail rigs were the trial horses for some of the early Rockford performance drive shaft products that they developed before formally making RCV a separate division of the company. Scoop watched my rig throw one half of one of the early prototype versions of their Extreme Spline shaft so far in to the woods at Paragon that I never found it. %)


One thing is certain and you correctly pointed it out; if you are disassembling a balanced and trued driveshaft assembly then you most definitely want/need to mark it and reassemble every componet in exactly the same orientation.

 

[DirtDonk]

Well maybe we weren't talking about the same thing the first time then? When I said "shaft sections" I was referring to the two halves on either side of the slip joint. Which is really the only "phasing" that I'm aware of being able to play with or mess up.
Were you talking about something else?

Paul

 

[Devin]

Well maybe we weren't talking about the same thing the first time then? When I said "shaft sections" I was referring to the two halves on either side of the slip joint. Which is really the only "phasing" that I'm aware of being able to play with or mess up.
Were you talking about something else?

Paul

I agree - what else is there to mess with?

 

[bmc69]

Well maybe we weren't talking about the same thing the first time then? When I said "shaft sections" I was referring to the two halves on either side of the slip joint. Which is really the only "phasing" that I'm aware of being able to play with or mess up.
Were you talking about something else?

Paul

That is exactly what I'm talking about.

The phasing of that section of a driveshaft is very important..critical even..when you have a single u-joint on each end of the shaft. In that case both of the u-joints must have the same exact bend angle ( 5 degrees..or whatever it is) and be aligned in plane (the phasing) or the velocity variation created by each bent u-joint will not be cancelled by that of the other one.

The double-cardan does all of that cancellation already. It acts as a constant-velocity joint and the long portion of the driveshaft is therefore spinning at constant velocity and there is no residual angular rotational variation to cancel. And this is exactly why the rear u-joint is ideally at a zero angle..so IT does not create an angular rotation variation that, since it cannot be cancelled out by an opposing u-joint, produces a vibration as a result.

 

[Devin]

Ok, picture as requested, Bax.

I flipped the slip shaft 180*. I haven't tested it yet. The more I look at this thing, the more I think it was pieced together. The front part of the shaft is shiny and new, and the rear part of the shaft, while it looks good, definitely has a rust layer on it.

 

[bmc69]

At first glance, I really don't see enough angle there to say that is where your problem is. Looks good to me...


How "tight" is the spline connection?

 

[Devin]

At first glance, I really don't see enough angle there to say that is where your problem is. Looks good to me...


How "tight" is the spline connection?

Spline connection feels great - just a touch of play, but not "loose". I recently re-packed it and looked at the splines - they look like they are in good condition.

 

[kc15842]

Did you check the pilot bearing/bushing when you installed the Trans? Sure looks like everything else is new and I agree with another post the rear pinion angle looks pretty darn close. I'm sure you checked the torque of all crossmember and mounts includng motor mounts. The harmonic damper is torqued and spins true?? Vibration hunting is a pain... good luck

 

[Devin]

Did you check the pilot bearing/bushing when you installed the Trans? Sure looks like everything else is new and I agree with another post the rear pinion angle looks pretty darn close. I'm sure you checked the torque of all crossmember and mounts includng motor mounts. The harmonic damper is torqued and spins true?? Vibration hunting is a pain... good luck

Pilot bearing/bushing thing is new. I used the special centering tool and everything. Crossmember mounts are tight, I haven't rechecked the motor mounts yet (but there is no vibration from the engine when I rev through the RPM range in neutral).

Harmonic damper was torqued, but I haven't rechecked that, neither.

 

[73azbronco]

one point on driveshaft angle I found is you need to have as small a driveline angle as possible but not less than one degree. That pic looks very close to less than 1 degree to me. No angle prevents needle bearings from turning.

 

[DirtDonk]

Two things come to mind still.

1. Are the two halves out of phase? What did you flip 180°? The whole shaft by rotating the joint in the yoke of the differential, or did you pull the splines apart and rotate the two halves of the driveshaft?
Flipping it 180 isn't what was a concern as much as just being 1 or 2 splines off. You just said you had it apart to re-pack the splines. Did this vibration start after that, or was it already going on?
When you sight down the length of the shaft, do the ears of the yokes on both halves of the driveshaft still line up still?

2. How much torque do you apply to the u-joint's u-bolts? Not much hopefully. They're only supposed to go down to something like 5 to 7 lbs (someone correct me if that's off) because much more and you can distort the caps and ruin the bearings.
Most people can very easily over tighten those u-bolts with just an open-end wrench or 3/8 drive ratchet.

You're right about the angle theory 73az, but in reality these pinions rarely stay static during driving. Each time there's even a mild amount of power applied, or you let off the gas, the pinion is constantly climbing or dropping on a Bronco.
Unless it's got a traction device or super-rigid springs, it's probably not a short-term problem.

Paul

 

[Devin]

As I stated before, I measure the angle, and it is 2.5 degrees. Picture does look fairly straight, though. The rig does have a traction device, also.

But, it doesn't matter. After flipping the rear slip shaft 180 degrees, the vibration is almost non-existent now. I can still feel a little bit of something, but I am happy with it.

The drive home was interesting. It was my first drive in major rain. My under-windshield seal isn't sealing worth a darn. Oh well, easy fix.

 

[DirtDonk]

...Oh well, easy fix.

In the Bronco-world, those are considered the very definition of "famous last words"!

Paul

 

[Devin]

In the Bronco-world, those are considered the very definition of "famous last words"!

Paul

Very true. But, I did jump out and take a look at the seal - it slid back quite a bit, and isn't clamped in there very well.