Gearbox help request
Turbo Mini Forums

Hope you've all been enjoying the festive break. My project has been to rebuild the gearbox I'm going to be using on the Marcos (eventually), and I've come across a problem I haven't been able to solve with the Search button - I'm hoping someone can advise.
I've reassembled the main gear shaft and thought it prudent to check engagement of the gears before carrying on further.
Selecting reverse - fine. Selecting 3/4 (I think) - fine. Selecting 1/2 (again I think) - not so fine.
With the syncro hub centered it looks like this:

Engaging one of the gears looks like this (fully engaged):

But trying to engage the other, this is as far as I can move it across:

Like I say, I haven't been able to answer this looking on-line and never having rebuilt a gearbox before am not sure if I'm being a wuss and need to yank the selector harder, but to me this should engage smoothly all the way (as the other three gears do).
Could it be the selector fork levers are incorrectly assembled onto the stud (with reverse definitely being the first/lowest)? Have I assembled the new baulk rings incorrectly (pointed bit inwards on both hubs)?
Thanks for any suggestions!

If it will engage one gear on the hub, it should be together properly. Only thought is about the baulk ring being in the correct place. Otherwise be a bit tougher on the change, they can be quite stiff until the engine oil was worked around the gears.

The left (geared) hub is for 1st and 2nd, the right hub (the one you're having trouble with??) engages 3rd and 4th.

Look at the dead centre of this photo; It looks like the 3rd gear teeth are perfectly misaligned. If the 3rd gear synchro is firmly wedged onto the gear, the gear and hub won't be able to realign themselves when the hub moves over. Just prise the syncro off the gear, align the teeth and try again. If it only goes part way, give the raised section of the hub a gentle tap with a drift in case its just a bit stiff.

On 29th Dec, 2014 Cooper1999 said:

Edited by PhilR on 29th Dec, 2014.

Cheers Gents - I think you were both correct.
Phil, a gentle tap with a brass drift knocked it over, so hopefully (Andy) it is correctly assembled.
When trying it again though I did manage to do this:

Bloody balls! I had enough trouble with these when assembling on the bench (though luckily, as researched with the 'Search' button, I'm not the only one ).
I managed to push the hub against the balls and, pushing them in with a screwdriver, get the hub back on!
What stops this 'over-through' in use?

Thanks again.

ETA So the hub on the right is 3/4, on the left 1/2. Thanks for the correction.

Edited by Cooper1999 on 29th Dec, 2014.

I was just about to say... Careful not to move it too far. It's a pain once your balls fall out.

In the 13's at last!.. Just

Oops, no, you don't won't your balls bouncing around.

There's a detent ball and spring that holds the gear change shaft in either 1st/3rd or neutral or 2nd/4th/reverse. Not sure whether that completely prevents this, but might be worth putting it back in temporarily.

Install the lay shaft before trying 4th

Of course - the ball and spring which engages in the three rounded positions in the 'hockey stick' shaped selector!
I'll continue putting it back together tomorrow (and it's 'over-throw' of course, not over-through'!) once I've adjusted the centre oil pick up (MiniSpares item but the hole for the mount next to the bend isn't quite right).

Thanks for the help

If you gave it a good whack, I think it could still overshoot even with the detent ball in though.

Andy's suggestion of temporarily putting the lay gear in is best. That way, you can't physically move the hub over that end gear, because it's meshed with the lay gear. Also, with the lay gear in place, when you rotate the gears it will break free any sticking synchros that could otherwise make it impossible to test any gears changes where the gears are misaligned with the hub.

Edited by PhilR on 30th Dec, 2014.

i found it helped to turn the box over as i pushed/pulled on the selector as phil said the bulk rings can stick a bit

Okay - so this is where I'm at.
I don't have a lower transfer gear and have done the nut up on the other end of the shaft by hand (both nuts to be done up to 150lb/ft?), but does only having a nut on one end cause the shaft to pull through thereby misaligning the gears?
Sorry if these are stupid questions, but I haven't been able to find an answer through the search button, haven't built a gearbox before, and am aware that the gearbox can be a weak area (albeit with more power going through it than I'll have).



Cheers (and enjoy your New year's)

Edited by Cooper1999 on 31st Dec, 2014.

Put the spring washer in the first motion bearing slot and put the third motion retainer on. That will keep everything nicely lined up.

You need to put the plate on that retains the main shaft bearing at the pinion end. (The C shaped thing with with 3 or 4 holes in.) That will push the bearing all the way in the housing and the gears will line up then. Torque up the mainshaft nuts to 150ft/lb by locking it in two gears at once. Theres not really any point in checking it works until you have at least tightened both ends.

You should also check the pre-load on that bearing. If you have a decent manual it should explain how.

dont forget the reverse shaft locking plate the little triangle shaped bit you can use that to help hold the shims in place to if you like buy pushing on the pin
you'll need the input gear to torque up the box

there was a few vids from minimania or some one regarding building a box

Get a metro Haynes manual rather than watching that twonk from MiniMania.

In the 13's at last!.. Just

Right - got myself an older Haynes manual (why did the remove so much gearbox info from the later books?) and have got the box together. I still don't have the lower transfer gear to be able to do that end nut up to 150ft/lbs, but have carried on rebuilding the diff.
Am I right in thinking I can't refit the diff until I've done the lower transfer gear nut (in order to lock two gears together).
In which case I'll put the box to one side waiting for the Marcos engine/box rebuild, and move on to the next bit of the project!
Thanks (again) for all the help and advice on here, and hope you all enjoy a great year!

Cheers,
Graham

With the diff fitted and the cover on, you can't dissengage the gear selector levers to allow you to lock the box.