Page created by T Apr 11th 2007:
The Universal Joints Need to Rotate:
Submitted by 74 HQ on Fri, 10/11/2006 - 01:28.
I am a mechanical engineer with 10 yrs experience. In order for a driveshaft that has a universal joint at both ends to work properly it requires that the angle created between the input shaft (gearbox drive shaft axis) and the intermediate shaft (axis of tailshaft) is equal to the angle created between the intermediate shaft (axis of tailshaft) and the out put shaft (diff pinion axis).
Further to this it is best to have some angle such that during a rotation of the shaft the needles within the universal joint are rotated somewhat. If the shafts are straight then brinelling of the needles can be encountered and premature failure of the universal joint may occur.
To elaborate. If the shaft is set up correctly and the input and output angles are the same then the input and output shaft rotation will exhibit a constant angular velocity whilst the tailshaft will actually speed up and slow down twice in one revolution. If the angles are different then you will transfer this speeding up and slowing down of the rotation through the input and output shafts which can lead to damage and noise of associated parts and also premature wear.
Further to this a single CV joint is like a very compact universal shaft with effectively an input, intermediate and output shaft within the joint where the input and output shaft angle are inherently, due to the nature of the joint, keep at the same angle to effective intermediate shaft and thus exhibit constant angular velocity on both sides at all time and thus not subject to require the same angles. Given this if you fit a drive shaft with a CV joint at one end and a uni joint at the other you eliminate the inherent problem of the conventional universal shaft and the input and output angles are no longer an issue. This is best.
Thus if you checked your angle at the gearbox in the same fashion as you have above then you need to adjust the diff until they are the same.
I have not followed your previous discussion so please excuse me if this is already been covered. I will try to dig up some pics etc.
If you require further elaboration then just holla.
Submitted by 74 HQ on Fri, 10/11/2006 - 01:33.
Ultimately you don't want them straight. It is not how they are designed to work as discussed above with respect to brinelling. Brinelling occurs when the needles do not rotate and thus stay in the same spot within the case all the time and then end up pressing into the case, constantly on the one spot, causing indents which is called brinelling. Then your rollers or needles if you like, have to roll around on a bumpy surface which is not good for a needle bearing and will add rise to premature failure.
Check this out for more discussion
Submitted by 74 HQ on Fri, 10/11/2006 - 01:39.
End of submission by 74 HQ
There is a welch plug in the front yoke of the tailshaft which can work loose and leak.
Tailshaft Yoke Welch Plug:
Submitted by v8slrtorana on Fri, 23/03/2007 - 09:59.
HQ to WB, LH to UC, VB to VK all have them. Any gearbox factory fitted to these models has a welch plug in the tailshaft yoke. Can create a very hard to find leak, especially with autos as the oil is much thinner.
End of submission by v8slrtorana.
HK - HQ Tailshaft Lengths:
Submitted by bf6379 on Fri, 22/06/2007 - 07:04.
Something I do know, is that a HZ Sedan 6 cyl (Trimatic, Banjo) tailshaft is exactly 26 mm longer than a 6 cyl (3 speed, Banjo) HT tailshaft.