Pete Lewis Posted January 4, 2019 Report Share Posted January 4, 2019 I wont say why we know these things We should sell forum clues tee shirts Pete Link to comment Share on other sites More sharing options...
gm38 Posted October 8, 2019 Report Share Posted October 8, 2019 Hello all, new to the forum so hope someone can help. Have just disassembled the single rail non O/D 'box from my spitfire 1500 and have a few 'what-if' questions. I did all the work on the top of the bench and was very careful when removing things, and didnt hear any strange "ping" noises when splitting the 3 sections apart, so bare that in mind please when answering: What would the symptoms be (hypothetically ofcourse) if; 1/ there were none of the 3 tension springs in the front end of the box, (the ones behind the front thrust washer) 2/ the layshaft anti-rotation pin in the remote end of the system wasn't fitted? Prior to taking the box out, the car was running well and the gears were selecting almost smoothly. There was a loud whirring type noise when I had my foot on the clutch in neutral, but I put this down to the clutch thrust bearing - which when I removed the box, looked fairly recently changed, just like the clutch and pressure plate. I've had the car since Aug '18 and have done ~2k miles with no issues, but think (uneducated thought) that this must surely have an impact. Thanks in advance for any input. Link to comment Share on other sites More sharing options...
johny Posted October 9, 2019 Report Share Posted October 9, 2019 Hi, Im wondering why you took the box apart now as the whirring sound, if not there with the clutch released, would seem to have been produced by the thrust bearing (is the bearing smooth to spin?). With the missing items 1/ are optional with some boxes having them installed from new and others not. They are intended to load the laygear thrust bearing to stop the gear rattling around when in neutral. However the pin in 2/ is always required to stop the layshaft spinning in its casing mounting holes (check this hasnt happened and the holes/shaft arent worn) but if the shaft was a tight fit its probably not moved anyway. The missing pin is sometimes to be found in the bottom of the gearbox somewhere.... The two main areas of wear in these gearboxes are the mainshaft tip and the layshaft, in both cases where the needle rollers run directly on the shafts as once the case hardening is damaged the softer metal inside can wear quite rapidly. Link to comment Share on other sites More sharing options...
Pete Lewis Posted October 9, 2019 Report Share Posted October 9, 2019 there are no backlash anti rattle springs fitted to single rail boxes , you can add 3 if you feel like it. noise with foot on is the thrust brearing,,, .....or serious crank end float !!!!! if the box was reasonable is there other reasons for wanting to strip it down do take note of how the remote spool selector fits m many remove it and cant re assemble its an odd bit of kit. if you strip the mainshaft reassemble case and shafts vertical so gravity keeps the 2nd gear collets in place or they drop out . look for any degrading of the mainshaft tip and as said the layshaft brg. surface if you split the 3/4th or 1/2nd hubs do it in a poly bag then you catch any escaping balls and springs Pete Link to comment Share on other sites More sharing options...
gm38 Posted October 9, 2019 Report Share Posted October 9, 2019 Thanks both. V helpful. I've got the springs now so will add in. Box was taken apart as a learning / curiosity exercise mostly, as the noise wasn't unbearable. Now for part 2 ..... Link to comment Share on other sites More sharing options...
johny Posted October 10, 2019 Report Share Posted October 10, 2019 Will you be doing anything else in the box apart from springs and pin? Was it perfect other than the whirring noise beforehand? For example you could check/swop around/replace synchro rings..... Link to comment Share on other sites More sharing options...
gm38 Posted October 10, 2019 Report Share Posted October 10, 2019 Johny, mostly looks okay, but I may take thew opportunity to change the symchro rings now i've got the thing to bits anyway. Reverse gear has a few 'chipped' teeth, the remnants of most of which seemed to have been caught by the magnetic plug on removal when draining the oil, which to be honest looked a bit like a hedgehog when i removed it to drain the oil when it was in the car. this is what made me think of removing the box in the first place, but then thought well why not. Link to comment Share on other sites More sharing options...
johny Posted October 11, 2019 Report Share Posted October 11, 2019 Hmmm sounds like someone has been slamming it into reverse - it needs a gentle touch, patience and the vehicle stationary when selecting.... With the rings there have been problems reported with the quality of repro replacements (the machining and material has to be spot on) so sometimes used originals are preferable. In fact you can inspect them and swop the most worn (usually second) for first or 4th. Link to comment Share on other sites More sharing options...
daverclasper Posted October 11, 2019 Report Share Posted October 11, 2019 10 hours ago, gm38 said: looked a bit like a hedgehog The hedgehog effect, is often just very fine particles, which is normal I think. Link to comment Share on other sites More sharing options...
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