19 replies to this topic

[fuzzypumper]

In my attempt to see where my vibration is comming from I got under the car and measured the angles.
The unis are good and the tranny mount is ok.
At normal ride height the tranny is .5deg down, the tailshaft is 1.5deg down and the diff pinion is 3.5 deg down.
So its only .5deg at front and 4.5 deg back.( I have nolathane busheson the back)
Now thats not right is it?
Shouldnt you have some more angle than .5 difference at the front to at least have movement in the uni joint
rather than it being almost straight?

[ls2lxhatch]

If the gearbox is down 0.5 degrees then the cancelled angle for the pinion is up 0.5 degrees. If you allow 3.0 degrees for diff rotation under load then the pinion would be set down 2.5

[wot179]

Dont touch it fuzzy,its spot on.

Look elsewhere for your vibration.

[wot179]

As it states at the start of this article,this is a contoversial subject.

I disagree with the opinion in the article and stand by my statement.

Diff pinion angle should be 2-4 degrees down.

Fuzzys car sounds like all angles are dead standard.

[ls2lxhatch]

The angles will be correct if the diff rotates 4.0 degrees under load which it probably would. When cruising at 100 km/h the diff will be under load and rotate up a couple of degrees from the static position.

The black art is in estimating the amount the diff will rotate for a given application. The perfect pinion angle for drag racing will not be the perfect pinion angle for a street car.

Edited by ls2lxhatch, 07 September 2010 - 06:40 PM.

[fuzzypumper]

OK, because my car is also slightly lowered I raised the rear to stock height and took measurements again
front became 3.5 and rear 5.5 deg, so only 2 deg difference now instead of 4deg.

The other question I still have is shouldnt there be some minimal angle the unis should run at e.g(like 3deg)
so rotation can occur for the needle bearings? If so my front only has .5deg , its practically straight.

[ls2lxhatch]

The operating angle of the gearbox uni is the difference between the gearbox angle 0.5 and the tailshaft angle 1.5 which is 1 degree. The recommended minimum operating angle for a universal joint is 1 degree.

Spicer Drivetrain Components - Driveshaft Installation

Rule 1: Universal joint operating angles at each end of a driveshaft should always be at least 1 degree.

Rule 2: Universal joint operating angles on each end of a driveshaft should always be equal within 1 degree of each other (one half degree for motor homes and shafts in front of transfer case or auxiliary
device).

Rule 3: For virtual vibration free performance, universal joint operating angles should not be larger than 3 degrees. if they are, make sure they do not exceed the maximum recommended angles.

[fuzzypumper]

Thanks for input guys,
For the moment I have replaced my current shaft with other one I have for the SLR which has
new unis in it and will over next weeks driving, see if that has made any difference.
I also may consider adding a plate under the tranny mount to increase the front angle from .5 to 1.5deg but this will
unfortunately increase the rear pinion angle too.

Yes, uni's need to work at an angle, I can't tell you what the optimum is, but I'm pretty sure it's more than half a degree.

Sorry to change the subject, but can anyone tell me why we don't use CV joints instead of unis in a tail shaft?

Didnt the 4cyl opel , manual tailshaft have CV joint on the front yoke? I distinctly remember that when I threw it out 20 years ago.

[hatchssv8]

Didnt the 4cyl opel , manual tailshaft have CV joint on the front yoke? I distinctly remember that when I threw it out 20 years ago.
[/quote]

Thats a definate as I remember throwing one of those out also.

I too am interested why we cant use as per the Sunbird. ie CV front and uni rear

[ls2lxhatch]

If the uni has a working angle then it will speed up and slow down as it turns through an ellipse. You need another uni to translate the pulsing power back into smooth power.

Driveshaft Angles

In travelling this ellipse, the U-joint speeds up and slows down twice per shaft revolution. A second U-joint having an equal but opposite angle is used to convert this pulsating power back into smooth power feeding the pinion.

Was the CV joint in the Sunbird actually a CV joint or was it a rubber uni?

[TerrA LX]

Shouldnt you have some more angle than .5 difference at the front to at least have movement in the uni joint
rather than it being almost straight?

They majority is right here, the shaft should be near straight as possible.
You do not want the uni joints moving around just rotating with the shaft.
The only reason they are "universal" is so the suspension can move around.

[ls2lxhatch]

Universal joints require about 1 degree of operating angle to get the needle bearings rotating. If the needle bearings do not rotate the joint will fail prematurely. A straight tailshaft will fail prematurely. In most cases the vertical angle between the gearbox and diff is sufficient. Where the vertical angle is not sufficient the diff will be set off centre to create the required angle on the horizontal.

The only reason CV joints are not used is cost.

Edited by ls2lxhatch, 07 September 2010 - 11:27 PM.

[76lxhatch]

CV joints are generally used in much more extreme angles than universals, in a driveshaft they would near last forever - the ones used in two piece Commodore driveshafts last a lot longer than a front wheel drive car's outer CVs for example

[rodomo]

And they're heavy.

[fuzzypumper]

Update.
It became immediately obvious to me that the spare tailshaft with new unis I installed drove with almost no vibration at all.
Looks like the tailshaft I had is out of balance. I rechecked the unis and they are OK.
I noticed the shaft had at one time been re-balanced as it had a non factory weight added.
I can only assume the balance was done with old unis before I replaced with new ones as was now out of balance again.

So who does a good tailshaft balance in eastern suburbs of Melbourne?