So there has been a fair old amount of detective work since the last update and plenty of research and learning. Last update I was basically giving the gearbox the once over checking everything would be ok for further use and since then I have made some further discoveries. The Spitfire 1500 or at least mine being one of the last 1981 had some revisions to the earlier gearbox models and mine is defo a mongrel. The early single rail gearboxes had a scroll seal on the gearbox input shaft. This is basically a reverse thread cut into the front cover seal to help retain any gearbox oil back away from the bell housing. You might be able to see the thread in this picture where I have removed the front cover seal. But again my car is one of the very last 1981 so why has it got a scroll seal as opposed to the revised rubber oil seal from around 1975 onward? It’s been changed or interfered with at some point in its life. The early scroll seals are a fairly good design and maintenance free, however they do have a tendency to allow a small quantity of oil past and dribble out the bell housing. This is accentuated massively if parked on a slight downhill slope and the gearbox full of oil. The oil level weeps its way past the seal and just makes a mess really, and the less contamination I have near the clutch the better really… so an upgrade or return to original is needed I think.
Before I could order all the relevant parts to complete the gearbox for install I firstly had to identify what my box was, and to be fair I’m still not 100% how old my box is. It’s definitely a single rail box so it’s a later box….but it’s had an earlier scroll seal front cover? So maybe it’s just had the bell housing changed at some point? I have tried researching the gearbox number, but it’s missing two number stamped on the deck FR153**. FR is the prefix for a UK supplied box on the 1500 it would be FT if it was a box for the US market. So it’s definitely a UK box… but the missing two numbers would lean towards a very early if not one of the first single rail boxes…. However they were a thicker 10 spline input shaft, and mine is definitely the finer 20 spline and further more the early 20 splined shafts were 12.5cm length from the input seal as opposed to the later 13cm shaft length….. my brain is frazzled now really.
I think to conclude this whole gearbox saga is that the internals and input shaft of the gearbox have been rebuilt and changed at some point in its life to a possible earlier gearbox casing and bell housing. This is not really any issues in my case as it’s only really when upgrading from the 10 spline input to the 20 spline input that you then have to start making changes to the clutch and flywheel etc… so I intend to rebuild to a later standard with the revised front cover seal and 1500 single rail spec etc. So rubber seal for the input shaft, replace the front cover seal in the bell housing and standard 1500 clutch. Off to order parts then… and hope they are right!
I took delivery of all the bits earlier in the week and I’ve been itching to get in the garage to make some progress and see if what I ordered and the changes I’m making will be ok. First up was the front cover seal as pictured here. These are easily fit into the bell housing similar to a bearing race but with the revision of a small scroll/locating pin to keep everything central, and I presume to make sure the tiny weep hole on the internal side is in the 6 o’clock position, so if any gearbox oil does get past the seal it will run down the bell housing as opposed to along the shaft and risk contaminating the clutch…. Logic! I fitted the front cover seal using my bearing drifts so I could be confident it’s was sitting home true in the bell housing. Aligning up the small pin was a tad fiddly but with the aid of a centre punch pushed through help it all line up nicely when it was being driven in. Then the rubber oil seal is fitted, in push back firm into the front cover seal plate. If this is not pushed back firmly into its position there is a risk that a circlip on the input shaft could void with the seal and mash it all up when it rotates, so attention here to the correct installation process.
On to the other side of the bell housing and something fairy crucial to a smooth clutch operation. I replaced the two brass bushes on the clutch arm pivot point, along with a tolerance clip that sleeves the pivot pin internal on the arm. You can’t really see the bushes here but they just push in to the casting fairy easy without any need to start hitting them. The throw arm bearing has also been replaced which was simply pushed on using the bench vice and all the associated roll pins and bushes. The throw arm pin was in perfect condition and was in tolerance of a new factory pin so no need to replace. If the pin was worn (shorter) then the clutch slave would not travel as far and thus a gritty slipping clutch travel which would not be very practical.
I fitted the new slave cylinder into its housing (pictured above) however I’m ashamed to say that the slave cylinder housing I have had to replace, as when I removed the old slave I have in error not removed the cylinder from its housing bracket and it’s all gone to the scrap…. Bugger. Not a massive issue but a £30 mistake I could have avoided. I had to grind a small amount of the replacement internal diameter as the new slave was no where near fitting nicely, or smoothly. So a small drum sander on the dremmal and it was soon sorted. The bell housing was now ready to be fitted back onto the gearbox. There is a gasket seated between the two faces and it’s simply bolted on from the internal of the bell housing with five bolts and lock washers. The lowest of the bolts is directly tapped into the gearbox casing which would allow the oil to drain, so a copper sealing washer is needed for this one. I belt and braces this one with a small amount of RVT silicon just to be safe… this is British Leyland manufacturing and pissing oil out is fairly mandatory…. But I’m trying my hardest to refine all these issues to reduce oil loss as much as possible.
With the bell housing and gearbox back in a steady relationship again it was time to move onto the engine side of things and get the engine end plate fitted, along with the flywheel, clutch, clutch housing etc… this is all very exciting for me really and it’s very enjoyable to be fitting all this back together. The engine crane was dragged from the back of the garage and the engine was quickly lifted up off its temporary home of the engine stand. The engine back plate is simply bolted on to the engine casting using a locating dowel and seven bolts and lock washers. I was amazed at what a low (in my opinion) torque setting was required for these so I did a bit of double checking online prior to covering them all with the flywheel.
Next up, flywheel and clutch. Having fun reading all this? I can assure you it has been very much needed progression for the build and just happy in the garage with the radio on all day… I definitely enjoy the building considerably more than the driving of all these projects I complete. The flywheel was fitted on its location dowel and the four bolts fitted and torqued down. I use a small amount of blue lock tight on these as despite them being new re-engineered bolts to a much higher tolerance than the original they still have no lock plate or any form of physical stop to stop them from working loose at 5000 RPM…. Three inches from you kneecaps basically…. But let’s not think about that! Let’s put faith in physics and trust it will work.
The clutch was fitted next with the clutch cover bolting it all down onto the fly. You need to use a splined centralising tool in order to align the clutch plate correctly. If when you have torqued everything down, you can not remove this tool easily just by sliding it out then the clutch plate is not central and will void on the gearbox input shaft splines or vibrate terribly when engaged with the engine drive. Once all that was sorted the gearbox could rekindle its relationship with the engine. It only took me a couple of attempts to lift the box back on and it slid nicely on and was bolted together accordingly. So now it was time to lift the whole lot onto the chassis and get it fixed down.
My previous test fit months ago when defining the engine mount positions was all a great success and the engine and gearbox were together again on the chassis. All the new engine mounts aligned perfectly and I have replaced the gearbox bush mounts also because for an extra £5 it’s stupid not too. I have temporarily fitted the prop shaft also. This will be getting a refurb and tart up along with replacing the universal joints etc.. but it was encouraging to roll the chassis out of gear and see everything working. It was even more encouraging to put the gearbox into 4th gear and then get engine rotation also when pushing the chassis… all in all a very productive and enjoyable day spent in the garage. And now the engine and gearbox are in it opens the window for loads of other jobs to get sorted as the build continues. I’m still awaiting delivery of the adjustable rear radius arms which will allow me to get the reinforcement plates welded on and fitted the we can start looking about getting the body into place, along with front bulkhead, rear bulkhead, pedal box etc… and altogether pushing the build on.
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