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Car Forum / UK Car Forums / Classic Cars (UK group) / October 2003A-series gearbox problem
25 years after it last moved under its own power, and after several abandoned restorations and five years of my intermittent labours, the Mk3 Midget was finally ready for its first trial: it managed about a foot before it jumped out of reverse and made horrible noises. I confess I had just crossed my fingers over the gearbox - perhaps that's why the car was finally taken off the road, rusted and worn out after ten years use. I've checked the obvious and easy bit, the reverse detent plunger and spring under the plug near the front underside of the 'box, and all seems in order there. The selector can be moved through the drain plug hole, takes its rod with it, and I can feel the neutral and in-gear detents. But it drops out of gear every time. Once or twice, it also made a horrible noise in first, as if the reverse idler was catching it. Anything to look at before I undo all my nicely copper-greased bolts and take the engine out again? I'll have a go at the side cover, and even cut an access hole in the tunnel if I can avoid taking the lump out again. Is there anything else that holds it in reverse gear apart from this one detent? -- A very glum Kevin Poole ********Use current month and year to reply (e.g. apr2001@mainbeam.co.uk)************** B270NZ, SA 1838, TC 8512, GAN3/48519, GAN4/63840, GHD5/324616 Tiltbed car transporter trailer hire - £25/ day. Near Derby. May even tow it for you. > Anything to look at before I undo all my nicely copper-greased bolts and > take the engine out again? I'll have a go at the side cover, and even > cut an access hole in the tunnel if I can avoid taking the lump out > again. Is there anything else that holds it in reverse gear apart from > this one detent? I'd say it's near certain you have damage to the first gear teeth on the layshaft which the reverse idler engages with. This could have been caused by rough treatment of the 'crash' first gear, or wear on the layshaft bearings causing the gears to drop out of mesh slightly. Either way, you're into a major gearbox overhaul. As a minimum, I'd replace the layshaft and bearings, first gear, and reverse idler. Oh - and the synchro baulk rings while you're at it, and of course check all the other bearings - especially the first motion shaft one. Not cheap, I'm afraid, so a secondhand one might be the best option assuming you can strip and check it first. Removing the side cover is enough to *carefully* examine the gears. Beware of cheap 're-cons' using secondhand parts. These are usually well less than satisfactory.  Signature*I didn't drive my husband crazy -- I flew him there -- it was faster Dave Plowman dave.sound@argonet.co.uk London SW 12 RIP Acorn > 25 years after it last moved under its own power, and after several > abandoned restorations and five years of my intermittent labours, the [quoted text clipped - 26 lines] > Tiltbed car transporter trailer hire - £25/ day. Near Derby. May even > tow it for you. I used to autotest a tuned-up Sprite many years ago, so I had plenty of experience with over-stressed gearboxes. (With practice, less than two hours from driving into the garage to gearbox free!) I found that they'd run with one or more teeth missing from first or reverse (as long as they weren't adjacent) but I never found that to cause jumping out of gear - just a *very* loud whine. More likely to be something in the selector mechanism at a guess, but I can't help you there. I tried repairing them on several occasions, but the result was always noisy so I gave up. I think once the teeth have settled into a wear pattern, once it's disturbed it's very difficult to get the preloads right. Much easier to get another from a scrappy then; now I don't know . . . Dave > I tried repairing them on several occasions, but the result was always > noisy so I gave up. I think once the teeth have settled into a wear > pattern, once it's disturbed it's very difficult to get the preloads > right. Yes. Which is why cheap re-cons are always noisy - they only replace the broken parts. IMHO, for a satisfactory job virtually all the internals have to be renewed. Signature*If at first you don't succeed, avoid skydiving.* Dave Plowman dave.sound@argonet.co.uk London SW 12 RIP Acorn "Autolycus" <aug2003@mainbeam.co.uk> wrote in message news:bmtlk4> But it drops out of gear every time. Once or twice, it also made a > horrible noise in first, as if the reverse idler was catching it. > [quoted text clipped - 3 lines] > again. Is there anything else that holds it in reverse gear apart from > this one detent? I've known selector forks to come loose on the selector rods in these boxes. That could give you the symptons you describe. Whatever it is, I don't think you can do much with the box still in the car. If it's of any interest I have 2 A series g/boxes. Both from Morris Minors. May not be the right type, but they did come out of running cars. I wouldn't like to say how good they are, only that AFAIK they are both working boxes. Mike. The message <1066593953.27140.0@demeter.uk.clara.net> from "Mike G" <mgibbs@clara.co.uk> contains these words: > If it's of any interest I have 2 A series g/boxes. Both from > Morris Minors. > May not be the right type, but they did come out of running > cars. They are different. Back in the 70s I bought a crap D reg Midget and shortly thereafter lost 2 gears. (2nd and 3rd IIRC). On dismantling the box I found the internals didn't correspond exactly to the diagram in the Haynes Manual (so what's new?). Turned out that the Minor 1000 box fitted had a brass or bronze locating washer for the gear cluster while the real thing had a more robust arrangement. I rebuilt that box but replaced it with a proper one from a scrapyard shortly thereafter. Roger > They are different. Back in the 70s I bought a crap D reg Midget and > shortly thereafter lost 2 gears. (2nd and 3rd IIRC). On dismantling the [quoted text clipped - 3 lines] > the real thing had a more robust arrangement. I rebuilt that box but > replaced it with a proper one from a scrapyard shortly thereafter. A D reg Midget should have had the baulk ring box which 1100cc Minor 1000s also had. Earlier boxes were much weaker. Signature*How many roads must a man travel down before he admits he is lost? * Dave Plowman dave.sound@argonet.co.uk London SW 12 RIP Acorn > > They are different. Back in the 70s I bought a crap D reg Midget and > > shortly thereafter lost 2 gears. (2nd and 3rd IIRC). On dismantling the [quoted text clipped - 12 lines] > Dave Plowman dave.sound@argonet.co.uk London SW 12 > RIP Acorn The Midget/Sprite ratios are different from the Minor, otherwise the boxes are similar. I have costed out replacing all the bits that wear and it's about ?100 - except the laygear of course which is megabucks if you can get one at all. I agree, there's really no alternative here to a proper rebuild. |
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