Thanks Toasty, pretty clever machining there by you to get that result.

You could be right.

I think I will just get Tom to make me a shaft & be done with it.

Hey, Ian. What kind of shafts are you running? CVs at the t-case outputs with u-joints at the diffs? You're running a solid front DS, correct? Not a two-piece like mine? Is the front DS a slip drive shaft?

What kind exactly and WHEN exactly do you get the vibration in 4WD. On acceleration, deceleration, steady cruise? At what speed? Does it steadily build? Or does it hit 55 and then start up?

"Driveline angles are not excessive, in fact quite mild."

Excessive/mild doesn't necessarily have anything to do with it. Drive line angles change over time.

If you've ruled out everything obvious noted above, its time to check and make sure everything still points where it should. When I have fresh springs, everything points exactly where it should, but after a couple years I start getting drive line vibration because the springs eventually sag as does transmission mounts, engine mounts.

Edward

hi Ed,

Both shafts have a double cardan at the transfer case & standard unis at the diffs.
Both shafts have a slip joint on the diff end.

Vibes come in around 80kph, seem to be more on deceleration.

I had all my angles assessed by a truck shop & have sent that info to Tom Wood. Interesting that the truck guy assesed the run out at 35thou on the front & 24 thou at the rear.
Thats more than my dial gauge said.



cheers

Ok, I thought so. I wasn't sure if you'd changed anything.



I strongly doubt very much run out has anything to do with this. That would be a constant and accel/decel wouldn't make any difference.

IMHO, you need to be talking to someone(s) else about drive shafts or have someone else do them for you. This isn't that complicated and from what I've read of your thread, you're having to jump through a lot more hoops than you should.

What's probably the issue is you have one or more CVs that are in need of rebuilding. However, from your description, it sounds to me like you have one that's getting close to needing rebuilt and you have one drive shaft that's either out of align or not aligned properly.

Since you didn't have the problem originally if I remember correctly, its probably going out of align. By 'out of align' I mean that your pinion is shifting enough to throw your drive shaft angle off.

That would explain the decel vibration but no cruise or accel vibration, because when you take your foot off the brake, the pinion is going to try and rotate the opposite direction from what it would normally do.

That means pinion angle wasn't set quite correct originally OR it was set right on the hairy edge and you've had enough wear and tear that the pinion angle is shifting JUST ENOUGH now that you're getting vibration. Over time this can easily happen - its how I know when my leaf springs are close to needing replaced.

A CV just starting to need rebuilding will give you that steady low level almost untraceable constant vibration. Put the two together and that sounds like what you described. Something else, too, if someone didn't rebuild a CV correctly, you'll get the same thing.

Quicky test - pull the front drive shaft, drop it in 4HI, and drive it around and see what happens. Replace the front and drop the rear and repeat. That'll tell you straight up whether I'm right or not and which ones doing what. Obviously, make sure you don't do this in AWD mode.

Edward

Tks Ed,

I dont see how the pinion could be out, it was OK before I did the transfer case swap.

I have tried it without the front shaft & its all good. Ive also tried it without the rear & it still gives the vibes.

I have sent all the info to Tom Wood for the angles etc. One of the things to come out of having the angles measured is that that because I had to clock the transfer case upwards a bit to clear the front torsion bar, that has got the front yoke pointing upwards at 5.5 deg. It then meets a downward pointing driveshaft of 3.4 degs, so that operating angle is 8.9 degrees.

Nope, if anyone tells you this that's BS. Even with the crazy angles I'm running with the SAS and the pasted together SYE on the front output of the Mitsu t-case, I could run 55-60 MPH in 4WD on the highway and it was so smooth you couldn't tell it was in 4WD.



No worries. It doesn't take much; sometimes all it takes is a bushing or mount sagging a little or loosening up to through everything off. In your case, since you're running IFS in the front, that's unlikely.

Ok. That means that the problem is in the front drive line. That narrows it down.



Ok, so ... you did what I got away from by running the split drive shaft. My front output yoke points up, too, but with the split drive shaft, by the time I'm to the CV, its flat with the frame.

5.5 degrees upward at the front output yoke, then downwards 3.4 degrees to the differential pinion. And, you have a CV at the transfer case and a U-joint at the differential. Starts about 80KPH and its an existing problem since the conversion.

Now, I have a question. How does the pinion, u-joint and CV line up? This isn't a u-joint/u-joint setup. The pinion should be in align with the drive shaft. You should be able to draw a straight line through the pinion, u-joint and drive shaft. The angle in a CV setup is handled by the CV, not the u-joint.

If you clocked the t-case either clockwise or counter clockwise from EXACTLY the OEM t-case output location, then the pinion is out of align. That means you would need to do one of two things.

1) Rotate the differential until the pinion is lined up with the drive shaft, OR ...
2) Clock the t-case until the pinion is back in align with the drive shaft

#1 is easier.

So the question is, what's the angle between your pinion and drive shaft? 'cause in IFS, that should be zero.

<edit> No, actually I think zero is incorrect. I think that should be +1 or MAYBE +2 degrees.

Neither CV or u-joints are too picky, and neither is the CV/u-joint setup. Until you start trying to do what you're doing. IME, 50 MPH is about where things start showing up if things aren't quite in align just right.

Edward

Ed,

I cant change the pinion angle & I cant clock up or down, the floor is in the way at the top & the torsion bar is in the way at the bottom. Its clocked in the only position it can go.

The front pinion isnt in line with the case or shaft.

Here are all the angles I had done by a truck shop.

Driveshaft

Speaking to Tom Wood , he has suggested a shaft with a double cardan at the yoke & a double cardan at the diff. I have sent him a Pajero front pinion flange & he is going to make me a shaft.

cheers

The front differential pinion has to be inline with the drive shaft. That's it. Not the case, the shaft. Looking at your diagram - if I'm reading it correctly - you need to rotate the front differential 2.3 degrees counter clockwise when viewed from the driver side.

I don't understand. I know you can't clock the t-case, but that's not where the problem is. You need to rotate the front differential. How can you not do that? There shouldn't be anything in the way that would prevent that. All you should have to do is modify the brackets that hold the front differential or make new ones.

That seems to be Tom's solution to everything. I talked to him several years ago. He wanted to do the same thing to mine. Ended up spending $500 here on the solution you have now - only my stuff is aligned correctly. Did he bother to tell you that that solution is more prone to vibrations than what you have now?

Edward

Ed, rotating the front diff would be a big job,

No Tom didnt say that 2 doubles would cause more vibes, can you expand on that. He has a reputation for quality work, you dont seem confident in him.?

I'll take a look at the FSMs tonight. I want to see a breakdown of the front axle assembly but from what I remember ...

There are two brackets that bolt the differential housing to the sub-frame. What you need to do is figure out how much you need to rotate the housing to get the 2.3 degrees, pull the front differential assembly, take the brackets off, weld up the original bolt holes and then re-drill new holes in the appropriate locations. And you're not going to be able to do this with a hand drill. If the bracket setup is like the Sport with both housing brackets at the housing, you shouldn't need to build anything up. I think I remember some Montero's have the PS bracket at the end of the axle tube rather than at the housing. That one may need to be built up.

OR, you can look at shimming the brackets at the sub frame to get the rotation. Sometimes that's possible depending on how its mounted to the sub-frame.

So, yep, I have a pretty good idea. Its not as bad as it sounds, though. I think I'd rather do that then pull the t-case, doubler and transmission.



Yep, he does. But every time I mention his name here to drive shaft guys they roll their eyes. He had me 98% convinced to do the double Cardan setup you're talking about. When I talked to the local shop that usually does my drive shafts, they rolled their eyes and told me that was ridiculously over the top, expensive and unneeded. I told them the same thing you wrote because that's the impression I had. All they'd say is, yes, he does good work, but its usually ridiculously complicated and expensive.

I'd be maybe willing to doubt the shops here, but I've never had them be wrong and Tom right. And, I've read too many posts on Pirate that all echo the same thing.

I don't remember all the little details. I was addressing this 5-6 years ago. What I do remember is that the shop strongly disagreed with running a double cardan setup on the street at high speeds. That with two joints I would be MORE likely to have high speed vibration. It has to do with having two big floppy joints vs a u-joint and cardan. The u-joint/drive shaft alignment holds the Cardan in place, so to speak. That doesn't happen as well as with a double Cardan.

And there is also the fact that Cardan's wear and are expensive to rebuild. Something to think about.

I know what I'm talking about is a pain, but its cheaper in the long run and based on my experience, I know that won't cause vibrations. I can run my rear drive shaft with a Spicer Cardan and a 1310 up to 5K RPM at 85 MPH and its absolutely glass smooth. I have NEVER talked to anyone with a Jeep and the double setup that can do that. So, YMMV.

Edward