Gear change problem on Caterham 6 speed Gearbox

[Grale2]

Hi All,

Does anybody know if these gearboxes can develop a fault that makes it very difficult to de-select 5th or 6th gear?

This problem has been progressively getting worse on my gearbox (only 6000 miles from new) to the point at which it is almost unusable. I have removed the gearbox and tried to identify the problem which I think is related to the selector rail and detent pin. If I remove the detent pin all gear selections/de-selections are perfect, but when I replace it with a low spring tension it still sticks in 5th/6th. 

I have included a few images that hopefully explain things better and also show extra wear on the 5th/6th locations on the selector rail.

Thanks

Dave.

[Tazio]

Speak to Phil at Road and Race Transmission.

[Wrightpayne]

Another simple thing to check - there is a breather on the top of the tail piece with 6 tiny dome head bolts - 4 at the corners and two in the middle.

Check the middle two are done up. If tight do not try and turn them as you may crack the loctite holding them in place. Under no circumstances take the middle bolts out whilst the breather plate is on the box!!

Under that plate is a metal bar which controls the left / right spring loading of the gear selector. A couple of years ago mine fell off and into the box, fortunately into the tail piece and not forwards into the gears!! Symptom was complete loss of L &R spring loading on gear stick.

Box out and eventually retrieved the bar through an 8mm x 40mm (ish) hole under the breather plate.

If not that, then as Tazio suggests go to a specialist - there are only a handful of people who truly know how to strip and rebuild them. A few years ago a strip, check and rebuild with no damaged parts was £350 ish IIRC.

Ian

[7 wonders of the world]

Steve @ SP Components in Redditch has some mods for these  

[Wrightpayne]

Steve rebuilt my 6 speed 1000 miles before the bar fell into the box.

Ian

[Grale2]

Thank you all for the advice.

After chatting to Phil at Road and Race Transmissions it is almost certain that the problem is the operation of the detent location pin. Instead of simply moving in and out, it is also rocking side to side which makes it more difficult to disengage from the selector rail. I understand this was an issue early gearboxes but as mine is circa 2013 I am surprised it has the problem.

Does anyone know how to determine the year of manufacture from the serial number?

Mine is - 70000CSR AAT0EK12

Thanks

Dave

[johnnyseven]

My 6 speed box is very stiff- especially going from 6th to 5th- can the pin be got to without removing the box?

[Grale2]

The following diagram shows the location of the detent pin (item 24). Unfortunately I cannot remember if its access was possible without removing the gearbox, I imagine it is tight though. My problem was the pin rocking, making it very difficult to come out of gear, maybe it would also be worth checking that the spherical bearing on the gear stick has free movement.