Clutching at deadlines.

With two weeks to go before the self-imposed deadline of getting the car back on the road for the 2018 McLaren Vale Vintage and Classic event, things were looking relatively peachy. I had the gearbox out, I had a clutch kit ready to install as well as all of the other bits and pieces I thought I might need during the process.  Surely nothing could go wrong? More on that later…

The first step was to remove the existing clutch from the car and inspect the flywheel for any scoring, rust or other damage. The clutch, a Borg & Beck style AP Driveline one, was actually in great condition and the friction plate was showing very little wear indeed. There was a little bit of scoring on the ends of the diaphragm spring fingers caused by the release bearing but nothing major. However, I had a brand new replacement waiting so I decided to keep this old one as a good spare and fit the new one anyway (if it had been a Laycock kit in equally good condition I may have chosen otherwise).

Old Clutch
Existing Borg & Beck style clutch

On removal of the clutch, the flywheel also looked to be in good condition with no significant scoring or corrosion to speak of.

Flywheel is in good enough shape


One item I had unfortunately forgotten to order was the spigot bushing which sits in the flywheel on the mk2 2500 (and in the end of the crank on the mk1) – this was noticeably worn and was a little loose so after a couple of futile phonecalls to Aussie-based suppliers, a replacement was ordered from the UK on express delivery. The bushing provides some support to the gearbox input shaft and is crucial to preventing wear in the gearbox bearings. The replacement bushing arrived a week later and when compared to the old bushing, its replacement was clearly well-overdue as the central aperture was not only heavily scored but also oval rather than round.

Bushes Old vs New
Old bushing on the right, new on the left


The spigot bushing is made from a porous bronze and needs to be soaked in engine oil overnight to provide ongoing lubrication to the end of the gearbox input shaft.  Its removal and refitting is relatively easy – I drifted the old bushing out of the flywheel with a suitably-sized socket and then used the old bushing to drift the new one in. The new bushing fits very well in the flywheel with no detectable movement at all, whilst the gearbox input shaft fits snugly but not tightly into the central aperture. It was the right call to delay installation of the new ‘box by a week to fit a new one.

Bushing Out
Old bushing removed from the flywheel


The next step was to take a look at the clutch release mechanism and to swap it over to the new ‘box. The clutch release bearing is pressed onto a bearing carrier which slides over the splined gearbox input shaft when being actuated by a fork attached to the clutch operating shaft. When the clutch pedal is depressed the operating shaft rotates causing the clutch fork to rotate and push the release bearing forward against the clutch pressure plate which, in turn, releases the pressure holding the clutch friction plate against the flywheel and therefore breaks drive from the engine.

The first obvious problem with the existing release mechanism in the old gearbox was that the two bronze slipper pads which act as a bearing surface between the clutch fork pins and the bearing carrier were missing – instead the pins were acting directly against the surface of the bearing carrier. Luckily, I had ordered the slipper pads assuming they would need to be replaced so this in itself did not cause any undue setbacks.

Missing Slipper Pads
There should be a square slipper pad on the end of this fork pin


The clutch release bearing carrier was removed from the gearbox (it can simply be pulled away from the input shaft when the clutch operating shaft is turned beyond the range that it would experience in normal use) and the taper pin holding the fork to the shaft was removed (along with its retaining wire). These pins are apparently prone to breaking which is a gearbox out job to replace, so I obtained a high-strength one from Chris Witor. The below picture shows the new pin holding the fork to the release shaft – to prevent undue stress on the pin it is preferable that the thread does not bottom out in the thread in the fork, mine was looking good in this respect.

Pin in Fork
The new pin does not bottom out in the thread in the fork, which is good news


Unfortunately this is where my luck ran out. On closer inspection of the release bearing carrier I noticed that opposite sides of its rear face showed C-shaped hairline fracturing – possibly due to fatigue from where the release fork pins had been acting against the surface without slipper pads or, perhaps more likely, just due to a previous ham-fisted approach to pressing the bearing onto the carrier. Either way it was very close to failure and a replacement was needed. I could not locate a replacement in Australia so yet another order was placed from the UK which will take a week or so to arrive. This sadly put me out of the running to attend the Vintage and Classic event in the Triumph but I’d rather miss out on this and know that I have not put sub-standard parts back into the car. I don’t really want to be dropping the gearbox again in the near future.

Fractured Carrier
Fractured release bearing carrier

So with work on the release mechanism halted, all that was left for me to do was to re-attach the flywheel (torquing the bolts up to the correct 50 lbf ft) and fit the new clutch kit. This went nice and smoothly and I know it’s properly aligned as I used some of the time spent waiting for international deliveries to strip down the old gearbox so I could remove and cut down the input shaft to use as a handy alignment tool. Hopefully this means the new ‘box should slide straight in without any issues.

Input Shaft Tool
New clutch perfectly aligned with help of a cut-off input shaft


Fitting the clutch was easy – the clutch plate is centralised against the flywheel with the help of the input shaft and the pressure plate located over the three dowels in the flywheel face. The plate is attached to the flywheel via six bolts, which were torqued up incrementally.

Now I am just waiting for Australia Post to deliver my parts so that I can move on to the next step in assembling the clutch release mechanism onto the new gearbox and lifting the new ‘box onto the car.


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