For some time now, I have been hearing a creaking and groaning from the rear axle area of my TF, particularly when moving off from rest. I thought it might just be creaking rear brake springs or possibly the rear axle spring U-bolts simply needed tightening up. With a long weekend trip coming up I decided to investigate.
I had previously purchased 4 new polyurethane spring pads that fit at the top and bottom of each rear spring (see illustration). These replace the standard rubber pads that tend to distort and deteriorate quite quickly. I also purchased 4 new U-bolts (SAX 093), 4 new locating plates (SAX 093B) and 2 U-bolt axle capping plates (SAX 093C) from the Club. The reason for the latter will become clear as we progress.
Dismantling to remove the old parts is straight forward as per the TD/TF Workshop Manual, remembering to support the weight of the car by blocking up with stands or secure jacks under the chassis forward of the rear spring. On my car, there are 8 5/16” BSF plain nuts locked together securing the U-bolts each side but your car may have 4 nyloc nuts doing the same job. Having cleaned up the U-bolt threads with a wire brush, the nuts are easily removed. This allows the spring assembly to gently drop down and assume its natural camber position while the axle hangs from the rebound straps. The U-bolts, locating plates and old rubber pads can now be removed and examined for wear.
Surprisingly for an area of the car that is normally thought to be firmly bolted together, I found wear marks in all the parts. The locating plates showed the U-bolts had been fretting against the hole sides elongating them laterally by about 1/32” (photo 1). The U-bolts showed clear fret marks of a similar depth where they sit in the locating plates. particularly at the upper plate position (photo 2). Furthermore, the U-bolts showed shiny wear marks at the top underside of the U where they had been fretting against the top of the axle, wearing two quite deep grooves each side of the axle casing. Now the reason for buying the 2 axle capping plates becomes clear, they are shown fitted in photo 3. These items became a standard fitting on the MGA for precisely the reasons shown up in the service life of the TD and TF.
Photo 1 – the U-bolts have been fretting against the hole sides in the spring locating plates elongating them.
Photo 2 – showing the corresponding fret marks on the sides of the U-bolts.
Photo 3 – showing one of the axle capping plates fitted on top of the axle.
This component wear confirms what we know now, that the TD/TF rear axle is not particularly well located laterally, allowing sideways movement to occur during cornering. I have read that the axle can move up to 1” across the car in extreme circumstances, causing vagueness at the back end. I am pleased to say I don’t think my car had reached that stage.
Reassembly is the reversal of the strip down process and both sides were easily reinstated in about 4/5 hours. A short road test revealed that the creaking and groaning noises seem to have gone and the car appears to steer more precisely.
I had previously fitted polyurethane rear shackle bushes to replace the standard rubber items. The Club also supplies these uprated items, part no. SAX 064c, (set of 4).
Ed’s note: Roy’s article first appeared in the September issue of the MG Octagon Car Club’s September ‘Bulletin’ and has been reproduced with their kind permission.