Wrong bolt removed from gearbox (oil filler)

[CraigShelley]

Hi,

My dad has asked me to post because he has unintentionally removed the wrong bolt from the gearbox on a 2002 Lupo and "bad things" have happened.
See photo.
A short google search leads to several posts stating that removing this bolt is a very bad idea!

When the bolt was removed, it was immediately obvious that this was not a filler plug, so it was carefully reinserted. However at a shallow depth it fowled on an obstruction within. Something within had fallen out of place.
After some perseverance, the bolt has (without forcing it) been inserted to a depth as shown in the photo, but at that point it starts to bind on something within.
The gears are now stiff, and it isn't possible to select reverse.

From a teardown video i saw on youtube, it appears that this bolt has something to do with maintaining the alignment of the selectors, but the video I saw wasn't all that clear.

We were just wondering if there was any way of recovering from this situation without having to remove and split the box?

Thanks in advance,
Craig

PS I was told initially that the car was a Polo, so apologies for posting to this forum.

[937carrera]

I don't know the Polo specifics, but from general knowledge:

This will be the retaining bolt for the selector rods. It will be an end cover off job. It "might" be possible in car, but whether it is or not, you will be better off whipping the box out. Check the clutch at the same time

Don't run the engine / gearbox any longer if you don't have to

[CraigShelley]

Thank you for replying.

I'm happy to report that we have been able to rectify the problem without taking the box off.
I visited my dad this evening and saw the problem first hand.
The selector for reverse gear was completely detached and rattling around inside the gearbox.

Here's a quick guide on how we were able to solve this issue:
By removing the filter plug, it is possible to "insert your finger" and fumble around inside the box.

Using a strong magnet on outside of the alloy casing helps to hold things in place while repositioning.
Having never seen what the innards look like, after about 4 hours of fiddling, I was suddenly able to picture how it worked, and where the selector needed to be positioned.

Diagonally up and to the right of the filler hole, you can only just touch the reverse gear. It rotates and slides left and right on its shaft.
Down and slightly right of the filler hole, you can feel a rectangular cut out in the reverse slider. Operating the gear stick into and out of reverse causes this to slide left and right.
The selector is a flat plate with a forked end, similar to an open ended spanner. Half way along, there is a hole, with a bush pressed in, which protrudes from the plate.
The hole in the selector must be aligned with the peg bolt which was unintentionally removed. The selector pivots at this point in a seasaw type action.
The bushing must be orientated to point towards the hole where the peg bolt is to be reinserted.

The first thing is to recover the selector from wherever it has fallen, and reorientate it so that the forked end points upwards, and the bushing points towards the front of the gearbox.
Using the magnet to help hold it in place, first push the fork up to the reverse gear. Ensure the reverse gear is between the two prongs of the fork.
Then slide the bottom of the selector into the rectangular cut out in the slider below.

A second person is needed to gently slide the gear stick into and out of reverse (forward and backwards) whilst holding the selector against the front of the casing with your finger.
Eventually the holes begin to line up. Using a very small drill bit to initially locate the centre of the bushing is beneficial. The alignment is very critical, several progressively larger drill bits will be needed to refine the alignment.
The peg should then insert without any resistance.

Removal of the reverse switch might be necessary if the selector becomes trapped, as it did several times for us.
Don't drive the car until the selector is reinstalled because the reverse gear is free to slide along it's shaft, and could engage while in a forward gear.
The magnet was essential, as it prevented the selector from falling back down each time you let go of it to reposition your finger.
Finally, you need to completely trust the person in the car moving the stick for you while your finger is in the box as a wrong move could be disastrous.

[937carrera]

Well Done !

Between the pair of you have been very fortunate and skilled to be able to remedy the situation without removing the end cover. Out of interest, it's about 4 hours to get the box off and back on again, if you know what you are doing

Thanks for posting back with the how to as well - it may help someone else in the future

You did remember to top the gearbox oil up at the end of the job I assume

[CraigShelley]

Yes, we did remember to fill up the oil! Thanks for the reminder.

I didn't mention that at some point in the process (when we had just about given up), we did remove the end cover. This obviously resulted in the remaining oil draining out, but unfortunately didn't help that much with the manipulation of the reverse selector.
Behind the end cover there is access to the 5th gear, selector and synchromesh. Immediately behind this there is a bulkhead which prevents access to the main gearbox chamber, where the reverse gear selector is located.
I think removing this cover was ultimately beneficial in building a mental image of what might be inside the main chamber from position of the visible portion of the shafts and slider rods etc...

I'm reasonably confident that this repair could be done in less than an hour having now gained the knowledge of what is inside, and where the selector needs to be positioned. I don't know what spanner rating the Haynes would give this, but it certainly requires a long thin middle finger!