Tail shaft phasing for VN. VP and VR, (V6?)

[vlad01]

Does anyone have the factory info on all the tail shaft phasing specs for the VN to VR v6, (v8 if it's different would be good to add here) for all the combos, auto, manual, sedan, wagon, model changes through the years etc...


I am on a hunt for this info as there was a clear reason they used angles other than 0 deg.

I think I found the reason or perhaps at least one of them.

Two of my cars with everything in top order with rebuilt and balanced shafts have been built the correct way according to the two places I had each of them done, which is apparently 0 phasing.

Well, for the longest time I have not been able to find the source of a violent shudder that starts at the rear left and continues to intensify and propagate throughout the car until even the front is shaking violently. Always happens when on the pedal on an on-ramp that goes up hill slightly, backing off for a split sec stops this shudder in it's tracks and resuming the pedal it most often never comes back.

So it's like a long left turn slightly up hill on full load that triggers it and as mentioned, starts at the rear left and moved forward until the entire car is like in an earthquake.

I have ruled out all variables and then it hit me, my other cars that don't have this issue still run the factory phasing, where the two cars with very different setups rear and engine mounting, suspension and all aren't the common denominators, but the tail shaft phasing at 0 being the two common things that aren't standard.


So I am pretty sure this is the issue, and my dilemma is that I need a new shaft built for the white car for the T5 conversion but I want to make sure they phase it to the factory T5/sedan specs this time, and not the 0 phase. If this prevents the shudder, I know that the white car otherwise will be apples to apples with one of the others that has this issue, but the difference will be the phasing. That way I can 100% confirm or rule this out.


My understanding though, is that depending on models, gear boxes used, sedan or long wheelbase etc... the angle can vary.

I have one tailshaft that is manual but it was rebuilt, it has the 37ish deg phasing, but I don't know if that is what it was originally, the yoke used to be the damper type, now a standard type, so I have no way to know with certainty if this is correct, however there is no shudder issue except from the rooted engine mounts and rear lower arms have fallen apart again, but this only vibrates under load in 1st when pulling a tandem trailer loaded up, else I have had no issues whatsoever, even this vibration only come about from the stuffed bushes and mounts.

If anyone has the factory manuals on this info, that would be awesome!

[vp304]

I got some vr vs workshop manual stuff mate i will have a look if i find something will post on here

[vp304]

Sorry only got for vs

[VK_3800]

With the CV in the middle you can end up with unusual angles to cancel not only up and down but also left to right, hence the difference for IRS. This changes significantly once things are worn or replaced with aftermarket items, e.g. can be very sensitive to the transmission mount. In the past I've found that even a small amount of shim can be the difference between massive vibration and none so that gives another avenue for fine-tuning.

If it were me I'd get the driveshaft made with the cardan joints exactly in phase when the shaft is straight as that will be hard to get wrong; if you already have one then this saves some time and money too. Adjust it ahead using the spline on the CV joint as described above, may need some experimenting for the best spot for your vehicle. If you're not sure if the vibration is driveshaft-related try one of those phone apps that measure harmonics, sit it on the shifter while driving at a speed that causes vibration and compare the frequency with revs.

[immortality]

I don't have any workshop manuals here but I've checked a couple of factory original VN T5 drive shafts and all have been slightly out of phase. I have a original somewhere in the garage.

[vlad01]

Wow this is a lot more complex than I thought looking at that chart.

I read up a bit on phasing and they still say 0, but that is on the assumption that both output of the gearbox and diff pinion angles are parallel throughout the rear end travel. As far as I can work out in my head, this would only be possible with a rear end with all 4 arms of equal length, but not many live axles cars can have this, so the two piece shaft makes sense as this allows the angles to not have to be parallel in absolute reference frame, but rather the same relative to the pivot point that is the CV, but I am pretty sure with unequal arms at the rear, this arc can't perfectly track the pivot point in the CV, so this phasing makes total sense to fine tune one position in compromise of another.

So, having 0 phase would make it really smooth when the car is level or weighed down, but on suspension extension the angle tends to tilt downward more than ideal if I recall ( can confirm this with the white car when I next do some more on the rear end), this could be the source of the hideous shudder that feels like the CV mount has failed (aka square wheel feel).

[immortality]

It's not just unequal length arms though, it's also rubber suspension bushes that allow the diff pinion to rotate up under load and back down on coast. There are lots of different dynamics going on but it doesn't explain the phase angle for IRS cars because the diff is in a fixed position and basically doesn't move (or move very much) so the drive shaft is fairly much working in a completely constant positions so much so that from VX2 onward they changed the drive shaft design to use the rubber doughnut coupling and did away with the uni's at each end.

[vlad01]

Yeah the bushes are at play for sure under certain conditions but not this condition it seems from my testing. Interestingly, solid superpro bushes all round didn't seems to be a factor in my case across the 3 cars I've been comparing. The shudder was the same with superpro installed. The only factor as mentioned that I eventually narrowed down to is this phasing.

As I pointed out it seems to be a long left turn thing too, which must be a road speed factor as well given the shaft is faster.I suspect that the car lifts off the axle a little more in that direction due to the torque placed on the axle in the clockwise direction looking from the front in combo of a certain shaft speed gets the wobbles going.

None of this ever happens in a straight line no matter the load or speed. Even at hard lower speed corners there are no hints of vibration.

Also, locking LSD makes no difference if that is any use. Billet engine mounts vs stock hydraulic, also no difference. Engines balance, stock and 50%, no difference, Bilstein vs OEM no diff. Two cars with 0 phase with these differences both do it the same, the other car some same, some differences, but zero issues and has a phased shaft that was built by one of the same mobs that did the other car with 0 phase.

So if I can't find definitive specs, I will just get them to do it the same as the shitbox with it's phased one as I know it works. I also have had that car airborne many times for fun years ago and never had any shudder with it's rear fully off the ground at speed.

At a glance, it looks to be 30 something deg + going by that chart.

[VK_3800]

doesn't explain the phase angle for IRS cars

Just speculating but I'd say there is still a somewhat-unequal angle front and rear due to a bit of sideways angle in conjunction with the CV and unequal length front and rear shafts. In comparison to the live axle cars the centre joint is in a different position (it's marked on the mount, it goes one direction for live axle and the opposite for IRS) so there is a sideways change to cater for. I've never really looked but quite possible the diff pinion has a different offset relative to the car.

[immortality]

doesn't explain the phase angle for IRS cars

Just speculating but I'd say there is still a somewhat-unequal angle front and rear due to a bit of sideways angle in conjunction with the CV and unequal length front and rear shafts. In comparison to the live axle cars the centre joint is in a different position (it's marked on the mount, it goes one direction for live axle and the opposite for IRS) so there is a sideways change to cater for. I've never really looked but quite possible the diff pinion has a different offset relative to the car.

The different centre offset for the IRS cars is to induce a angle over the uni joints, if it was fitted the same as the live axle cars the uni's would fail a lot sooner as the shaft would basically be inline from the transmission to the dif. Uni's need a few degrees of angle to ensure the roller elements actually roll ensuring a long working life.

Yeah the bushes are at play for sure under certain conditions but not this condition it seems from my testing. Interestingly, solid superpro bushes all round didn't seems to be a factor in my case across the 3 cars I've been comparing. The shudder was the same with superpro installed. The only factor as mentioned that I eventually narrowed down to is this phasing.

As I pointed out it seems to be a long left turn thing too, which must be a road speed factor as well given the shaft is faster.I suspect that the car lifts off the axle a little more in that direction due to the torque placed on the axle in the clockwise direction looking from the front in combo of a certain shaft speed gets the wobbles going.

None of this ever happens in a straight line no matter the load or speed. Even at hard lower speed corners there are no hints of vibration.

Also, locking LSD makes no difference if that is any use. Billet engine mounts vs stock hydraulic, also no difference. Engines balance, stock and 50%, no difference, Bilstein vs OEM no diff. Two cars with 0 phase with these differences both do it the same, the other car some same, some differences, but zero issues and has a phased shaft that was built by one of the same mobs that did the other car with 0 phase.

So if I can't find definitive specs, I will just get them to do it the same as the shitbox with it's phased one as I know it works. I also have had that car airborne many times for fun years ago and never had any shudder with it's rear fully off the ground at speed.

At a glance, it looks to be 30 something deg + going by that chart.

Lowered cars?

Have you tried adjustable top arms to change diff pinion angle?

I drove a manual VN for years, never had any issues, was lowered too where as the our old VS had some weird drive line vibes and that one was basically FE2 spec suspension but with stock drive shaft. I suspect it might have actually been a our of round wheel.

But then, I don't think my old VH had any drive shaft phasing, and yet it's the same design drive shaft, same design rear suspension and I don't remember that having any issues and that thing was slammed. I've driven Commodores with stuffed rear uni's and they didn't vibrate either, just a clunk coming on/off the throttle.

From what I have seen/read over the years, this was something Holden chased on the VN-VS range of Commodores but never totally resolved. Different phase angles on drive shafts, voided bushes in the rear suspension upper arms were tried too somewhere IIRC but never actually fixed the reason for the odd vibes.