Gearbox vol. 3

[Horatio]

Hi,

I just bought a gearbox from a Danish company, who promised that it was a reconditioned box. However, when accelerating in 2nd and 4th gear, the box jumps out of gear..

So - 2 questions:

1) My old gearbox made a rattly sound in 2nd gear at 3-5000 RPM when "off boost" and sometimes also in first and third gear (off boost too). It dissapperead more or less immediately, when the clutch was engaged. Furthermore, when loosening the upper bolt of the gearbox last week to check the oil, metal filings "clamped" to the bolt.

Can I be absolutely sure, that the noise does come from the gearbox? And what would be needed to fix it (which parts etc.)?

2) The reconditioned box did not have the sounds (though hard to check as it was not possible to put it in 2nd and make it stay there). But what is needed to fix those two gears and would it be insane just to renovate 2nd and 4th gear?

Thankful for advice, since I have already bought and installed one gearbox without the anticipated success.

P.S. I live in Denmark, so the UK suppliers of gearboxes are not possible to use..

[XRV848]

Jumping out of gear is usually the result of not fully engaging the gear in the first place. The gears are engaged by a collar that locks the selected gear to the shaft. If it is jumping out of gear then it is probably caused by the locking collar not moving through the correct distance. This can be caused by worn selector forks, by an incorrectly installed shift arm assembly (within the gearbox) or incorrectly assembled shift mechanism (outside of the gearbox).
The first check should be to make sure that the gearshift cables are correctly fitted and nothing is preventing the full range of motion in the 2nd/4th gear direction.

[Horatio]

Ok - thank you very much for the explanation XRV848! Anyone on the other question?

[XRV848]

Sorry Horatio, I missed your first question, but I think that you've answered it yourself as the noise has gone with the new gearbox.
The fact that the noise disappeared when you disengaged the clutch indicates that it was caused by one of the rotating components from the clutch friction plate onwards. As it was in specific gears, that would probably rule out the clutch and final drive and therefore point to bearings within the gearbox. As to what parts are needed to fix it, that can only normally be determined by opening it and stripping it down. If there is a significant amount of debris on the upper bolt (oil fill plug?) then, when you open it, it may be obvious what has broken. You do not state which gearbox this is, although the problems suggest that it is a Midlands 5 speed on an early Cooper or One.
If you bought the 'box from a reconditioner and you are sure that your installation is correct (especially the shift cables), then surely the best course of action would be to get their opinion on the problem?

[Horatio]

Hi XRV848!,

Thank you again for a very fulfilling answer. It was the oil fill plug that had a lot of metal "stuff" attached to it. And the 'box is a Midlands - I was just wondering if it was worth the trouble to actually fix the box before passing it on to somebody else. I can see on Ebay that some people sell "recon-kits" but it is difficult for a guy like me to know if the bearings offered are the ones I need. Maybe it is not really worth the trouble after all.

The "scrapyard" where I bought the box has surprisingly (to me, at least) been very helpful and will fix the problems - so I guess I am not THAT unlucky after all.

Thanks for the kind help and advice, I have already learnt a lot about gearboxes now.. :-)