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Thread: Side-Change Gearbox Stuck in Top Gear

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    Side-Change Gearbox Stuck in Top Gear

    I was out in my BN7 on Saturday and I had to stop at traffic lights. When I went to shift the gear lever into neutral, it wouldn't move and the gearbox has remained stuck fast in top. There were no nasty noises or any signs of trouble before and up to then the gear box shifted perfectly.
    I was able to continue home in top gear without any difficulty.
    Does anybody have any idea what is the cause and how I can fix it.
    I would be grateful for any advice.

    Crusty
    Last edited by Editor_Reid; 02-16-2020 at 11:26 PM.

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    Yoda
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    Re: side change gear box stuck in top gear

    Was the box recently rebuilt? There are three (I think) spring-loaded balls and springs that go into the dog(?) gear to hold gears, if one or more is somehow jammed that would cause the problem. I assume you've tried to 'pop' it out with as much force as you felt comfortable with; too much and you could break a shift fork. If you're not able to pop it out I think you have no choice but to remove the side cover and have a look (I think you can do that in situ, no?).

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    Re: side change gear box stuck in top gear

    Hello Bob,
    The gear lever is stuck fast. I have used a fair bit of force but I have been afraid if I use too much I might make the problem worse. It was suggested that I rock the car back and forth and this might free it up , but no success there either.

    I am not sure what to do now. I could take the side cover off, and you are right , it can be done in situ. My worry here is that I wouldn't have a clue what I am looking for or even at. If something has fallen off or out, where has it gone to. I think I will do as you suggest and see if I can find someone who knows about these old things to make a home visit.

    I am dreading removing the gear box from the car though.

    Thank you for your advice You have given me a starting point.

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    Jedi Knight Keith_M's Avatar
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    Re: Side-Change Gearbox Stuck in Top Gear

    Having just rebuilt my sideshift, I can offer a little help. Bob is right that the problem could be with the detente balls that engage the shafts holding the forks. There are three balls that are spring loaded on the side of shafts, one for each shaft. You will see these three balls and their springs when you remove the side cover. There are also two balls between the shafts, one above the center shaft and one below. Those two balls prevent you from moving one shaft while another shaft is in the "engaged" position. It's possible that one of those balls has gotten jammed somehow so that you can't move the 3rd and 4th gear selector fork shaft. You should be able to access the three spring loaded balls by removing the side cover, but I think you will have to remove the whole tranny to get at the two balls between the shafts because you have to remove the forks and shafts to get to them.

    If the problem is not those detente balls, then it could be something more serious with the 3rd and 4th gear shaft or the sliding hub that selects one of those two gears.

    Good luck,
    Keith
    Keith
    '59 Bugeye (recently restored)
    '62 BT7 (recently restored)
    '65 Sprite (restored 30 yrs ago)

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    Yoda
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    Re: Side-Change Gearbox Stuck in Top Gear

    I think the first thing to try would be to drain the oil into a clean pan and see if any metal comes out. You will have to do that to remove the side cover anyway, and if chunks of metal come out you'll know you have to pull the gearbox no matter what.

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    Re: Side-Change Gearbox Stuck in Top Gear

    Thank you both for your comments. I will see how I get on this weekend and report back.
    I expect most of the Forum is thinking Thank God it's not me!!!!

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    Re: Side-Change Gearbox Stuck in Top Gear

    http://www.britishcarforum.com/bcf/s...al-Replacement,

    @Crusty, I posted this guide to removing my side-shift transmission. If you decide to do it, it can be done, I did it 3 times.
    Tim K.
    1960 3000 BN7 (owned since 1981)
    1973 Yamaha TX500 (Owned since new -- 11,000 lifetime miles)
    Former LBCís: 1961 TR3, 1966 MGB (SCCA race car)
    First car: Volvo 122S

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    Re: Side-Change Gearbox Stuck in Top Gear

    Quote Originally Posted by Crusty View Post
    Thank you both for your comments. I will see how I get on this weekend and report back.
    I expect most of the Forum is thinking Thank God it's not me!!!!
    So how did you make out? My bet is that something happened at the synchro hub, preventing the engagement sleeve from returning to neutral.

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