In phase or out of phase?

[IBCRUSN]

Yes, that is what the guy told me. That being said it might be a good idea if there are issues to contact one of the regular 4x4 driveshaft shops such as Woody's. The guy I worked with knows his stuff but his thing is racecars where angles aren't such a problem.

KS is going well. Work is another issue all together. By the way where are you now?

 

[60wag]

Ok, this "front shaft out of phase" thing has me puzzled. I know the book shows it that way but can anyone come up with even a lame reason that makes sense for assembling that way? I usually have respect for the original design intent but this one looks a bit whacked. Anyone?

 

[lowtideride]

I was always under the impression that u-joints "vibrated" and by putting them out of phase from each other the "vibrations" canceled each other out. So putting it in phase would cause more vibrations.

 

[chibo]

http://www.pirate4x4.com/tech/billavista/PR-shaft/index2.html

 

[Tools R Us]

Ok, this "front shaft out of phase" thing has me puzzled. I know the book shows it that way but can anyone come up with even a lame reason that makes sense for assembling that way? I usually have respect for the original design intent but this one looks a bit whacked. Anyone?

I was always under the impression that u-joints "vibrated" and by putting them out of phase from each other the "vibrations" canceled each other out. So putting it in phase would cause more vibrations.

I agree, had this conversation with the driveshaft shop last week. They agreed that the broken back and out of phase setup is unique, not common, but couldn't come up with any good logical argument for the out of phase part.

 

[scottm]

I was always under the impression that u-joints "vibrated" and by putting them out of phase from each other the "vibrations" canceled each other out. So putting it in phase would cause more vibrations.

Correct. They vibrate in rotation: they accelerate and decelerate as they rotate. If you have a U-joint in your socket set it's easy to see this. Snap two extensions to each side of a U-joint, and spin one end. When the joint is straight, the output shaft will spin smoothly. As you flex the joint while spinning, the output shaft will spin more erratically, it's accelerating and decelerating twice per rotation.

If you add another U-joint and extension, you simulate our driveshafts. If the second U-joint is 90-degrees out of phase with the first, it will accelerate when the first U-joint decelerates, and decelerate when the first U-joint accelerates. So it cancels out the accelerating and decelerating, and the third shaft (diff) will turn smoothly. If it's in phase, it'll further accelerate and decelerate the third shaft. Driveshaft U-joints should always be 90-degrees out of phase, but that can take some complex geometry.

For the joints to perfectly cancel, the two joints have to have the same angle (bend). If the input (t-case) and output (diff) are both horizontal, and directly in line along the truck, the joints will always have the same bend as the suspension travels up and down. That's how our rear driveshafts work. The rear suspension hinges on long arms to keep the rear diff fairly horizontal. You'll notice the three shafts (in the t-case, driveshaft, and in the rear diff) are in the same vertical plane, they don't bend to the side like the front driveshaft.

The front driveshaft is more complicated: the three shafts aren't all in one plane. They don't have to be for this to work, but the joints have to be rotated so they bend at the correct phases to cancel each other. At stock height and normally loaded, they are correct. With the suspension stretched or compressed off-road they aren't correct, but there won't be vibrations at the low speeds encountered off-road. A lifted 80 might experience vibration because the front U-joints no longer cancel each other on the road, you might need to experiment or take some measurements to get that right.

Continuous velocity (CV) joints don't have yokes, and don't have this problem. They're more complicated, more expensive, harder to maintain, heavier, and less efficient, but take up less space than pairs of U-joints. Birfields are CV joints.

 

[60wag]

Hmmm.... I totally get the standard driveshaft case (80 rear shaft) with the shaft accel/decel as it rotates. I'm still having problems with the front shaft. Even if the tcase flange is offset to one side relative the the pinion, That should have no impact on the phasing as long as the two flanges are reasonably parallel. I guess the aern't parallel in the stock config as the have been described as a "broken back" arrangement. The Pirate article touches on the "broken back" design but then shows the flanges phased the same as a conventional arrangement - although the pic is really small and hard to say for sure. I need to spend some time under my truck pondering this.

 

[MJADDICTION]

Does anyone else find this funny? Or am I just delerious from dealing with a contractor all day?

Ashooter asked the question. Then the last post is talking about Broken Back Mountain...

Oh, this is funny.

On the subject though. I had mine balanced in phase after new u-joints. The d-shaft had a vibe above 50 mph. got worse with more speed.

I took it 90 out of phase, and most of the vibe was gone, even without rebalancing the shaft.

Shaft, ashooter, and Broken Back... Anybody hear some banjos?

 

[raisinhell2]

yes, Dan is correct.

I just found the supplement which was hiding way down in the propeller shaft section of TIS.

It corrects the earlier schematic I posted and indeed does show the front drive shaft as being "out-of-phase"

My bad and I apologize for providing the incorrect information in my initial post.

Here is the supplement pic.
View attachment 74716View attachment 74717

Sorry to dig up such an old post . I have been hearing this for years chalking it up to mud experimentation and over thinking . I'll be damned if i didn't open a FSM for a 97 and it shows it out of phase for any other vehicle in the world By what Toyota calls for . I have never in my life installed a driveshaft out of phase. I worked for PST in Fl for a few years we built driveshafts for all the street outlaw guys and NASCAR. never did we send out any shaft out of phase. I also called Tom woods today and they confirmed My thoughts. As far as I can remember the FSM has been law to me . I never claim to know 1/10 as much as the Toyota engineers. This is a very hard pill for me to swallow and makes no sense. Even more so to a guy who has balanced 1000s of drive shafts..Do you or @cruiserdan have any theory to go along with the supplement to the why, this was done this way?

 

[OGBeno]

Sorry to dig up such an old post . I have been hearing this for years chalking it up to mud experimentation and over thinking . I'll be damned if i didn't open a FSM for a 97 and it shows it out of phase for any other vehicle in the world By what Toyota calls for . I have never in my life installed a driveshaft out of phase. I worked for PST in Fl for a few years we built driveshafts for all the street outlaw guys and NASCAR. never did we send out any shaft out of phase. I also called Tom woods today and they confirmed My thoughts. As far as I can remember the FSM has been law to me . I never claim to know 1/10 as much as the Toyota engineers. This is a very hard pill for me to swallow and makes no sense. Even more so to a guy who has balanced 1000s of drive shafts..Do you or @cruiserdan have any theory to go along with the supplement to the why, this was done this way?

No idea. I have some assumptions/theories. But that’s it.

 

[peacesells63]

Sorry to dig up such an old post . I have been hearing this for years chalking it up to mud experimentation and over thinking . I'll be damned if i didn't open a FSM for a 97 and it shows it out of phase for any other vehicle in the world By what Toyota calls for . I have never in my life installed a driveshaft out of phase. I worked for PST in Fl for a few years we built driveshafts for all the street outlaw guys and NASCAR. never did we send out any shaft out of phase. I also called Tom woods today and they confirmed My thoughts. As far as I can remember the FSM has been law to me . I never claim to know 1/10 as much as the Toyota engineers. This is a very hard pill for me to swallow and makes no sense. Even more so to a guy who has balanced 1000s of drive shafts..Do you or @cruiserdan have any theory to go along with the supplement to the why, this was done this way?

At stock height, the front shaft of an 80 is closer to a "broken back" configuration than traditional. Traditional, the tcase and diff flange angle should be paralell. Broken back, the flanges are opposite angles from 0 degrees and the drive shaft is 90 degrees out of phase to get to maintain cancellation of the elliptical pattern u joints run in when at an angle. Once you lift an 80 2-3" and correct caster, you end up very close to a traditional configuration. About 4" of lift with 4 degrees of caster and the flanges are paralell. Long story short, at stock height it will run a little smoother being out of phase. Lifted, the vibrations will get worse with every inch of lift considering caster has been corrected for the lift. Its a radius arm problem more than anything.

 

[DC2NoVA]

At stock height, the front shaft of an 80 is closer to a "broken back" configuration than traditional. Traditional, the tcase and diff flange angle should be paralell. Broken back, the flanges are opposite angles from 0 degrees and the drive shaft is 90 degrees out of phase to get to maintain cancellation of the elliptical pattern u joints run in when at an angle. Once you lift an 80 2-3" and correct caster, you end up very close to a traditional configuration. About 4" of lift with 4 degrees of caster and the flanges are paralell. Long story short, at stock height it will run a little smoother being out of phase. Lifted, the vibrations will get worse with every inch of lift considering caster has been corrected for the lift. Its a radius arm problem more than anything.

So just to clarify -- it sounds like if you have 2"-3" lift and castor correction, then you'd want to run your driveshafts in-phase? ignoring the FSM guidance of 90 degrees out of phase?

 

[peacesells63]

So just to clarify -- it sounds like if you have 2"-3" lift and castor correction, then you'd want to run your driveshafts in-phase? ignoring the FSM guidance of 90 degrees out of phase?

Correct. You will get a pretty gnarly vibration if you run out of phase above a 2" lift.

 

[peacesells63]

That video is the best explanation out there of driveshaft phasing and angles. It does not demonstrate broken back configuration, but I have tested it myself on a similar demo setup at an industrial trade show. 90 degrees out of phase does not work for every broken back angle, but you can find the sweet spot that has the least to no change in speed by playing with phasing.

I originally learned about this because 20 years ago we had a rock crawler break the poorly welded spring perches loose on a trail. Where the truck was at we could rotate the axle, so we welded them in where they were with the pinion pointing sky high. Previously the owner had been complaining about a driveshaft vibration because his driveshaft was out of phase. On the drive home he said it was smoother than ever before, so he left it like that. I did a bunch of research on it and found an explanation in an old Studebaker manual. Studebaker and land rover used broken back configuration in a few factory vehicles and its really common on farm equipment.

 

[raisinhell2]

At stock height, the front shaft of an 80 is closer to a "broken back" configuration than traditional. Traditional, the tcase and diff flange angle should be paralell. Broken back, the flanges are opposite angles from 0 degrees and the drive shaft is 90 degrees out of phase to get to maintain cancellation of the elliptical pattern u joints run in when at an angle. Once you lift an 80 2-3" and correct caster, you end up very close to a traditional configuration. About 4" of lift with 4 degrees of caster and the flanges are paralell. Long story short, at stock height it will run a little smoother being out of phase. Lifted, the vibrations will get worse with every inch of lift considering caster has been corrected for the lift. Its a radius arm problem more than anything.

I already knew all of that and agree with what you said. . I was looking for official Toyota tech info to why they did what they did. if I'm going to break 45 yrs of experience of doing it differently with zero adverse results. I wanted to see the reason why from Toyota made such a radical change. As I said before to me the FSM is law My shop lives by it . Sadly I need more Toyota tech info on this before i install a drive shaft out of phase on purpose.

 

[cruiserdan]

In my experience Toyota doesn't usually spend much time explaining reasoning. They simply say "do it like this".