Gear Change issues

[ColinMarr]

In recent years, when I read accounts of restorations or ambitious remedial works, I am often full of admiration for the scale and thoroughness involved, just as now. So, it comes as a surprise to find something that I thought relatively easy to do being a problem to my more proficient contemporaries. I had to think again about taking the gearbox out with the engine in-situ and I am convinced it wasn’t a problem. My Aprilia was a 1939 Lusso – perhaps the late-type cars like mine were more roomy around the gearbox, but my recollection is that it was an OK job to do. Happy days …. 

[Raahauge]

I am surprised at the variation of difficulty with selection and am having difficulty in visualising what may have gone wrong inside the box to cause it.
They are very nicely made and in my experience very reliable. Having said that I broke the gearbox shaft at the prop coupling last year (it happens apparently) which has given me the recent experience of engine removal and also gearbox assembly.
I think it may be something external like a loose gearbox cover or one of the pins holding the gear-lever has come out. It would be lot of work removing an engine to just find that out. Would you describe your difficulty as lost motion, ie not being able to move it far enough or stiffness?
I have always remover the gear-lever complete and never considered just unscrewing the tube, a much better idea, and no risk of losing the rag that I stuff in the hole.
I have several boxes in various states so I can probably help with bits if needed.
Mike

[DavidHill]

I have taken the top off the gearbox...and cannot see any immediate issues with the selector mechanism (see attached photos)

[Raahauge]

It looks to me that the detent in the RH selector shaft is quite close to the selector, I will see if I can dig out a box tomorrow and see if it is the same.

[DavidHill]

some more investigation this am has zeroed in on the issue....the left hand selector rod (which works on 1st and 2nd i assume) can be moved forward and backwards by hand easily and the detent spring moves up and down nicely with a satisfying "snick".  The right hand rod does the same (which i assume is for reverse)...but the middle rod (which is for 3rd and 4th i assume) cannot be moved at all...and the detent spring wobble a bit when i try to move the rod....so i think the detent mechanism under the spring is broken/jammed...

Any suggestions on how to remove/fix it???

[DavidHill]

further investigation, i removed the spring and the cap holding the detent ball bearing (38-21014 and 38-21015) and then looked at the ball bearing (48022)...it is intact and can be rotated...so I now suspect that the gears themselves are jammed?

[DavidHill]

Further on the gearbox, i have now taken off the selectors and the selector rods...no sign of any issues with them....the large cogged sleeve that should move to engage the 3rd and 4th gears does not move...so i now think its something blocking that...

[simonandjuliet]

Have a careful look at the exploded diagrams for the cogged sleeve, there is a ball bearing or something in the middle. I am not at home at the moment so can't look , but seem top remember that there is a subtlety in there - I see if I have anything with me so I can check

[williamcorke]

38-20008 - 'GRANO reggispinta manicotto innesto 3a e 4a velocità' / 3rd and 4th clutch sleeve thrust grub screw

49403 - 'RULLINO per manicotto innesto 3a e 4a vel.' / ROLLER for 3rd and 4th speed coupling sleeve

Missing in your photo?

[DavidHill]

Hi William,

I think there is a grub screw visible (38-20008) in the middle photo, should there be one on both sides  and i am not sure the 49403  is there...again should there be just one of them and any ideas where it should be?

[williamcorke]

Hi David,

I'm sorry to say I've not taken an Aprilia gearbox apart (beyond taking the cover off to check the condition of the gears) and so can't answer your questions.

Let's hope Simon or someone else here can shed more light - I partly posted the Tav in case Simon (not at home) might find it useful!

Best, William

[Raahauge]

I think it is not a grub screw, its a pin that in conjunction with the ribs on the mainsheet locks a gear in place when another is selected, clever.

[DavidHill]

yes that small part 38-20008 is present and looks to be fitted correctly (see pic)...so I do not think it is causing the jam....my next step is to start dismantling the box and removing the cogs and shafts to see what i can find.  Noel has kindly sent me a copy of the "servicing The Aprilia" guide which outlines how to take it apart.  First step find an oven that will take the whole gearbox as it has to be heated to 80C to remove the shafts!

[simonandjuliet]

Hi David
Have a look at the Cabrio thread, about page 16 for some gearbox pictures, including the oven !

[davidwheeler]

The bearings have grooves in the outer race into which fit the locating pin/bolts which must first be removed.   Then place the box in a moderate oven and the bearings will come out sweetly.    If the bearings are worn, the grooved outer race type is no longer available I think but you can cut a suitable groove in the race with a this grinding/cutting disc if you are careful.     Worked for me anyway.
A problem with the Aprilia box is falling out of third gear due to wear on the dogs and grooves of the third/fourth sleeve.    I have no idea if new parts are available but Simon may know.