Thread: What is it with me and prop shafts?

I can relate to your pain mate! I had a front uni go about a month ago...spent a frustrating hour at 10pm by the side of the road taking it off. I'd only greased the props the week before - when I replaced the uni I found that the grease had only gone to three points on the spider leaving the other one dry. I'm now greasing them every 2000km and making sure the grease comes out of all the points.

I just did some googling and the closest bearing supply places are either at Wagga Wagga (around 50km from Tarcutta) or Tumut (around 65km from Tarcutta) - here's the link. Hope that helps a bit and you're able to get it sorted soon!

Bugger!

I have a front tail shaft from a 200TD1 Defender, here at Horsley Park, Western Sydney. Trouble is we are heading down to Callala Beach tomorrow morning.

I can leave it with our neighbours for pick-up or I can have it Express couriered if this is of any help. Also I have a a pair of spare Unis.

Please let us know ASAP.

In the mean time see if you can get your tailshaft removed - 2 x 14mm ring / combination spanners, so you can still be mobile, driving with the diff lock engaged.

PM me if I can help.


Erich.

Ball and roller race bearings do not need a large amount of grease in them. Being clean and dry inside is important though.

My uncle, who ran an engineering business reckons that an SKF Bearings rep once said to him that if it wasn't for grease nipples, they wouldn't sell as many bearings. In other words, probably more bearings failed though over than under greasing.

This would sometimes be due to nipples not being clean and dirt forced in with the grease, but more often damage to the seals from regular forcing of grease thriugh them and sometimes from heat generated from extra friction with bearings full of thick grease operating at high speed. When damaged, grit and water are more likely to enter.

If seals are not perfect, after operating in water, greasing immediately afterwards is a good idea to blow the water out.

A problem particularly applicable to universal joints is that some greases are more inclined than others to set like cheese. As`well as not moving around to provide lubrication, it would be more inclined to block up one passage in a unijoint cross so grease all goes out through the others where there is less resistance. Sometimes pushing the shaft hard towards seals grease is coming out of while pumping hard can blow this stiff grease through. Probably a good idea to check recommended greases. Most likely not something also preferable for applications like steering ball joints.
Another factor which increases likelihood of universal joint failure is the shafts running straight all or most of the time. Most types of couplings last longest when perfectly aligned. However, in universal joints this causes the load to be in the one place all he time, resulting in corrugations developing on the bearing surfaces where needle rollers contact and earlier failure. For applications using universal joint couplings where positions of the driving and driven shafts are fixed relative to each other, normal practice is to deliberately misalign them slightly to stop this problem.

So far, the only universal joint I have replaced on my 130 Defender is the rear one in the rear tailshaft, which runs virtually straight. I have rarely ever greased them, but with several years of drought, water has not been a problem. Note some car unis do not have grease nipples. If properly lubricated on assembly, it seems they do not necessarily have a shorter life than greasable ones.

Another point to note is that Hardy Spicer type universal joints are not constant velocity joints. When the shaft is operating at an angle, the injtermediate shaft after the universal joint is alternately ahead of and behind the driving shaft twice each revolution. it is important that the with two universal joints, they both bend at approximately the same angle and the second one is doing the opposite of the first, cancelling this out.

To achieve this, the two yokes on the intermediate shaft must line up. Shafts attached to tractot power take offs that are in two pieces that can slide in and out can usually only be put in the one correct way. However, the equivalent on a 4WD tailshaft may have 16 splines. There are two correct and 14 incorrect ways of installing them. Mechanics not aware of this frequently put them in wrong. When 90 degrees out, the irregularities add up, not cancel out when shafts are not running straight. This causes vibration and extra stress on the unis.

One notable exception has been practised for some years on the front tailshaft of Defenders: Angles the two unijoints run at is different and it has been found that there is less vibration problem if the shafts are connected so the unis are running 45 degrees out of phase compared with what is normally regarded`as correct.

Last but not least, proper installation is important. Considerable force is required, and new unis can be damaged if too much is applied if bearing cups start going in crooked.