1st and 2nd gears locked

[cooper66]

Hello Genlemen,

On my freshly rebuilt S1 65 4.2 i have a strange issue. Background, engine, clutch and gearbox new (approx 200km...). With this very hot weather arround 35/40, after 50/60km drive when gearbox oil is hot, it becomes impossible to select 1st and 2nd gear while reverse and 3rd/4th continue to be perfect. Engine is at normal operating temperature, gearbox is running with EP90, and before it locks 1st/2nd selection is very smooth.

I investigated and this is hoepfully not coming from the synchromesh but from selector itself. By removing the gearbox top cover I discover that when hot the striking gear of 1st and 2nd becomes impossible to move. After 1/2 min it come back to normal ...

Any idea ?

[cooper66]

Hello,

issue still not solved, here is a video showing the mecanism after 1st/2nd are becoming "locked". Any idea ?

clutch is working properly as 3/4th gears and reverse are operating normally.

[angelw]

Pierre Wrote:

I investigated and this is hoepfully not coming from the synchromesh but from selector itself. By removing the gearbox top cover I discover that when hot the striking gear of 1st and 2nd becomes impossible to move. After 1/2 min it come back to normal ...

Hello Pierre,
If you're saying that the 1st/2nd Gear Selector Rod can't be moved in the Top Cover with the Top Cover removed, then that would rule out the Synchro Hubs. In your video, slight movement of the 1st/2nd Gear Selector Rod can be seen, but seems to come to an abrupt stop in both directions; accordingly, the Selector Rod can't be seizing in its respective bores in the Top Cover. Only that either 3rd/4th, or Reverse can be selected during the time when 1st/2nd is jammed, it would be a reasonable assumption to make that the Lockout ball and rod mechanism at the front of the Top Cover is the cause.

Can the issue be replicated by heating the Top Cover (whilst its removed from the Gearbox) with a Hot Air Gun. If so, I would remove the two Ball Bearings and Rod that make up the Lockout Mechanism and see if the issue still occurs when you replicate the condition that causes movement of the 1st/2nd Gear Selector Rod to be inhibited. If the problem disappears with the Lockout Mechanism removed, then you have a more focused area to investigate.

Regards,

Bill

[cooper66]

Hi Bill, thanks for the advice. The ball bearing you mention is the following element (n°20) i guess ?

I will make the test tonight

[angelw]

Pierre Wrote:

The ball bearing you mention is the following element (n°20) i guess ?

Hello Pierre,
Yes, there are two and the small rod that should be between them.

Regards,

Bill

[PeterCrespin]

Testing when stationary is not the best check, because you can sometimes get gears jamming in a way that doesn't happen if you spin the cluster a little. Even having someone turn a back wheel with both in the air, can be enough to overcome baulking. However, you report this happening during driving, so it is unlikely to be that, and it normally only happens on one gear change rather then an opposite pair. I agree there may be an interlock ball or pin issue. Odd though...

[cooper66]

Thanks for the advice, I take it back to the workshop for an overall check of the mechanism, let's wait friday !

[cooper66]

Gentlemen, you were right, it was the ball bearing ... everything is ok now I did 400km and the gearbox is perfect

Topic closed.

[Heuer]

Thanks for the feedback! Most refreshing to have confirmation of a fix as some posters just 'hit and run'.

[cooper66]

This forum is a gold mine, full of relevant informations, happy to contribute.