How safe are your stub axles?

11 Nov

As my ownership of TC4985 approached its first year I performed my first full service. I had read that the stub axle spindles, after many years of hard driving, are prone to crack and break off! So, I decided, as part of the service, to remove the hubs to inspect the spindles.

In the process, I discovered that the stub axles had been put on the wrong sides! Sherrell (page 102 of TCs Forever) says “The Near Side (L/H) stub has a left hand thread; the Off Side (R/H) has a right hand thread;” To me this means that the nut on the N/S stub is turned anti-clockwise to tighten it, which is the opposite way to the N/S spinner. However, anti-clockwise movement loosened the nut! Consistently, the O/S hub retaining nut needed to be turned clockwise to loosen it. Actually, I found that the O/S nut was only finger tight! As confirmation of this, I also noticed that the steering stop bolts were missing and the holes into which they fit were forward of the axle rather than being to the rear. This bolt, with the domed head of the cotter pin that holds the kingpin in the axle, creates an end stop for the steering. In the photo you can just make out the empty hole.

So, apart from wanting to inspect the spindles, I now needed to swap the stub axles (the hubs were on the correct sides). The spindles, however, looked fine, even if there was some discolouration on one, perhaps indicating some corrosion. Even with the use of a jeweller’s glass I couldn’t see any signs of cracks.

I couldn’t find any significant play in the kingpins, so bought new cotter pins (with domed nuts), new thrust washers, some shims and two steering stop bolts from Roger Furneaux. The existing cotter pins were not of the right type (and were different to each other), but came out easily by undoing the nut to the end of the pin and hitting the nut with a hammer. The kingpin then came out by tapping the end with a wooden dowel between the pin and the hammer. In fact, the kingpin bushes are different on each side and one is upside-down, having the spiral grooves taking the grease away from the thrust washer. But I decided to leave them alone for the time being.

Now we start getting to the reason for writing this article. Some people on the mg-tabc online group (https://groups.yahoo.com/neo/groups/mg-tabc/info) said that I should do a crack test on the spindles whilst they were off the car. Others said these spindles are old and fatigued, just replace them and be safe. Having read the section in Sherrell on replacing spindles I knew that the job was beyond my capability and so I decided to do a crack test, to prove that it wasn’t strictly necessary to take this fairly, drastic step.

So, I bought a dye penetrant kit, sprayed the cleaner on to the spindle and dried it, then sprayed on the purple dye and left it to work its way into any defects for 20 minutes. The dye was then cleaned off and ‘developer’ sprayed on, again leaving it for a while. One photo shows the spindle covered in dye and the other shows the underside of the spindle covered in developer.

The line of red dye at the root of the spindle is about 15 mm long! The other spindle had a purple line about 5 mm long. Prior to the test I couldn’t see these cracks with the naked eye or with a jeweller’s glass, but they were enough to convince me that I needed to replace the spindles. It is said that you can hear when a spindle is about to break because the brake linings start rubbing! Firstly, I’m not sure that my untrained ear would notice the new sound and secondly, I would rather that they didn’t break while I was driving the car!

As a result, I bought a pair of spindles from Bob Grunau in Canada and Eric Worpe was kind enough to fit them for me. The next photo shows the stub axles as returned by Eric, but after I had painted them. I had removed all the paint before taking them to Eric, since I knew that they would need to be heated (and the new spindles cooled) before the spindles are pressed in.

The final photo shows one of the renovated stub axles fitted to the axle before the brake backplate is fitted and the steering links connected. The new spindles have a 3/4” UNF thread (rather than the original 5/8” BSF) and so it is necessary to buy right-hand and left-hand threaded TD retaining nuts.

We bought an extra pair of spindles from Bob, so Eric has (or at least had) a spare pair waiting to be fitted to someone’s TC. How safe are your stub axle spindles?

David James


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One Response to “How safe are your stub axles?”

  1. Peter Jones 29. Dec, 2016 at 1:01 pm #

    Actually it is the brake drums that rub on the back pates that warn of Imminent failure–trust me, I know about these things !

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