Drive shaft UJs

[4129R]

I have just spent most of Sunday trying to replace a drive shaft UJ on 2420R, a Twin Cam.

First the circlips were rusted in badly, and did not want to come out. After careful bashing with a hammer and chisel, I managed to get them out and then press the cups out of the yokes.

Getting the new cups with the needle bearings into the yokes has proved a nightmare. Eventually I got 1 pair in, but the second pair on the driveshaft won't go in far enough to put the circlips in.

Normally this is because a needle roller has fallen in, so the cup won't go the final bit, but all the needles are in place, and there is no room for the circlip. The two sides of the yoke are definitely not bent, as I made up a 27mm bar long enough to go through both to check they were true and in perfect alignment.

So next weekend I will carefully grind even amounts off the opposite sides of the X that fits in the cups.

We are only talking about 2mm at the most, so 1mm each side.

Has anyone else had problems getting the circlips in? The cups are quite an easy fit in the yoke holes, so circlips are needed to stop the cups coming out with centrifugal force.

[jbcollier]

In the course of pressing the joints out, it is common for the yokes to collapse inwards slightly.  Use a long punch and spread them out a bit and then the circlips will fit.

Once they are in place, I open up the vice to support the horizontal yoke and smack the body of the vertical yoke down to fully seat the cups against the circlips.  I use a lead hammer so as not to damage or mark anything.

I’ll make a post with photos next time I do one.

[4129R]

But if they collapsed inwards, the 27mm bar I machined to fit through both to check they were in line, would not fit through both holes.

The [ would be more C.

It goes straight through, which should prove they have not moved inwards. 

[jbcollier]

Driveshaft yokes are not hardened steel.  They are actually quite soft, the better to take shock loads.  I have changed hundreds of them.  Very common to have to spread them slightly to get the circlips in, especially with the smaller joints.

[4129R]

I have just ordered 24mm studding, nuts and washers, to push the yokes apart slightly.

I hope this works.

I had bent 1 arm on the yoke that was stuck on the gearbox diff output shaft. I soaked it in WD40 and then used a 2 arm puller, and it came straight off.

To straighten 1 arm of the yoke, I anchored my hydraulic press to the garage wall, found a socket which fitted exactly through the splined hole, clamped the socket and therefore the yoke, in the press, put my machines 27mm bar in the bent yoke arm, attached a 4ft scaffold pole to the bar, and 5 seconds later the yoke was straight again.

This time, I need to ease both apart very slightly, so using studding and nuts should ease them both apart equally.

[4129R]

Problem solved.

It was a combination of the yoke closing up slightly and the circlips holding the needle roller cups in the yokes.

The yoke was out of square by 1.5mm, so I put it in the press, used the 4ft scaffold pole, and eased it apart until the measurements top and bottom were the same measured with accurate calipers. 81mm I seem to remember.

The new circlips are thicker. The new ones are curly Cs, the old ones had very small rings in the ends. So I rummaged through my collection of old UJs for the ring ones, found about 10 candidates, cleaned them all up on my trusty and very well used circular bench wire brush, then measured all the thicknesses, and picked the thinnest pair, which went straight in to the yoke. There was 0.3mm difference in the thicknesses, so 0.6 for the pair, which made all the difference between fit and no fit.

The rear drums are now rebuilt completely. The TC rear brake drum assembly is quite different from the TCS. The TC has manual adjustment as opposed to the wheel thingy operated by the hand brake lever. The shoes and drums are thinner on the TC, the wheel cylinder is different, the springs holding the shoes together are different, and the T thingy with the spring which holds the shoes to the backplate is longer. Also the hand brake lever is a different shape, so virtually no interchangeability of parts between the TC drum and th TCS drum.