19 replies to this topic

[Shtstr]

Hi all.
As most of you know I'm doing a conversion from an holden adventra into a lx hatchback.
Due to the fact that I'm running the vy adventra floor pan i have the option to run a one piece or 2 piece tailshaft.
Just wondering what others would do if they had the choice of either one and why.
Car won't have more than 400hp at all 4 wheels.

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[Oversteer]

What rear axle you using ?

[rodomo]

You'll struggle to balance a single shaft over 5000rpm...............but I don't think you'll be racing this?

[Bigfella237]

So many questions need to be answered first...

 

The biggest advantage of a two-piece driveshaft is their ability to correct driveline angles that two uni joints alone might have trouble with. The position of the centre bearing can be used to split the difference of an extreme alignment issue. But then you have the added initial expense and the hassle of mounting the centre bearing to consider.

 

Do you have any idea what your driveline angles will be once everything is in situ? Are you using a live axle or IRS?

 

The other advantage is with the critical speed of the driveshaft, speaking vibration-wise, the two short lengths of a two-piece shaft are treated as individual shafts so with both being very short (compared to a one-piece shaft) they have an extremely high critical speed, usually way above any practical limitations. This also allows for much smaller diameter, lighter shafts.

 

If you like I can crunch the numbers but I'll need a ton of info like rear tyre size, diff ratio, driveshaft lengths (uni centre to uni centre), shaft diameter, material and wall thickness, and the specific uni joints used (like 1310, 1350, etc.)

 

In conclusion, the two-piece driveshaft will likely cost more and require more initial setup, but will allow much more flexibility and probably have less vibration issues if set up right.

 

EDIT: DOH! I need to learn to type faster...

Edited by Bigfella237, 31 January 2018 - 09:58 PM.

[Shtstr]

What rear axle you using ?

Cross 8 crewman diff modified to fit the torana.

[Shtstr]

So many questions need to be answered first...
 
The biggest advantage of a two-piece driveshaft is their ability to correct driveline angles that two uni joints alone might have trouble with. The position of the centre bearing can be used to split the difference of an extreme alignment issue. But then you have the added initial expense and the hassle of mounting the centre bearing to consider.
 
Do you have any idea what your driveline angles will be once everything is in situ? Are you using a live axle or IRS?
 
The other advantage is with the critical speed of the driveshaft, speaking vibration-wise, the two short lengths of a two-piece shaft are treated as individual shafts so with both being very short (compared to a one-piece shaft) they have an extremely high critical speed, usually way above any practical limitations. This also allows for much smaller diameter, lighter shafts.
 
If you like I can crunch the numbers but I'll need a ton of info like rear tyre size, diff ratio, driveshaft lengths (uni centre to uni centre), shaft diameter, material and wall thickness, and the specific uni joints used (like 1310, 1350, etc.)
 
In conclusion, the two-piece driveshaft will likely cost more and require more initial setup, but will allow much more flexibility and probably have less vibration issues if set up right.

Diff is live axle.
Mounting point is alread in floor pan.
Front shaft will be std adventra and only rear section would need to be shorten

[Shtstr]

As for pinion angle it will be fine as it was said by splitting it ove 2 shafts it works well.
Car is only a cruiser/ show car.
Only thing I'm concerned about is that the rear shaft being so short 4 to 500mm not much room for movement of live axle and pinion angle.

Edited by Shtstr, 31 January 2018 - 10:02 PM.

[rodomo]

The centre joint is a constant velocity joint???? and will cancel any problems with unis either end.

[Bigfella237]

The centre joint is a constant velocity joint???? and will cancel any problems with unis either end.

 

Yes to some degree (no pun intended ) but anyone who owned or worked on a VN Commodore would know about all the driveshaft alignment problems they had from new. And the factory's warranty solution was to decouple the CV joint and move the unis out of phase!

 

Only thing I'm concerned about is that the rear shaft being so short 4 to 500mm not much room for movement of live axle and pinion angle.

I'd say then that you'd be better off shortening the front section of the rear driveshaft and moving the centre bearing forward to suit?

[Shtstr]

The more people say the more I'm leaning towards a 1 piece shaft.
Will not be moving the center bearing as the mount is fixed in the floor already.

[Bigfella237]

BTW, pinion angle is only one piece of the puzzle, especially with such a custom install.

 

Beside static pinion and thrust angles (assuming the rear suspension geometry is even travelling through the appropriate path), you will also need to verify that engine/trans assembly's position in the car in relation to the diff pinion is correct (or at least the same as it was in the Adventra) both vertically (looking from the side of the car), longitudinally (looking from above), and laterally (looking from the front).

 

All up there's like 8 different axis's (axes?) to account for, no matter what type of driveshaft is used. All of this is carefully calculated by new car designers but in this case, guess what... that's you!

[Shtstr]

Horizontal vertical and front to back is same as adventra to the center bearing. From there it is slightly different due to live axle over irs as the diff pinion is slightly different in height and not fixed in place.

[Shtstr]

Well all within a couple of mm

[76lxhatch]

It will come down to the operating angles of the driveshaft uni joints, so do some proper measuring to see how a one piece shaft would end up first. A lowered Torana puts the engine and trans so low that the diff pinion cannot point down (which is the normal position) if you want to have opposite cancelling angles, pointing the diff up when you weld the mounts on might be one option (edit: but watch out for clearance to floor/tunnel).

If you do go two piece don't rule out something so simple as moving the centre bearing mount, with the amount of work you're doing its nothing and could solve some problems.

I have a two piece driveshaft (VN style with CV centre joint) because I couldn't fix driveline vibrations any other way without major changes. Completely fixed it and gives me flexibility with different transmissions if need be.

Edited by 76lxhatch, 01 February 2018 - 03:49 AM.

[Shtstr]

Will wait to see where it lands.

[Peter UC]

It seems everyone has missed that fact it will have an independent rear end. The diff height can be changed to get the correct uni angle height if need be, however if given the choice I would run a two piece shaft.

[Bigfella237]

It seems everyone has missed that fact it will have an independent rear end. ~

 

@Shtstr already said above that it will have a live axle, not IRS.

 

Horizontal vertical and front to back is same as adventra to the center bearing. From there it is slightly different due to live axle over irs as the diff pinion is slightly different in height and not fixed in place.

[Peter UC]

Oh this is from a ute not an Adventure, my bad

[Bigfella237]

As above, the donor car IS an Adventra wagon but the hatch is getting a custom live axle, not the IRS.

 

Although considering the amount of work already done to fit the engine/trans/front diff & suspension, I think I would've gone the extra mile with the IRS myself, but maybe there was some reason not to?

[axistr]

I would go for two piece. it will give you more flexibility when everything needs to be aligned. Just keep in mind the CV joints don't allow

for as much movement in and out like slip joints when the suspension travels. This may depend on your diff assembly mounting angles.

 

I used a Nissan GTR centre bearing in mine, rated at 650hp but told they can handle 1,000hp.

 

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