Section : Gearbox

Clutch, gearbox, overdrive, propeller shaft.

Jumping out of gear

Posted By : Stewart Sloan, 22-Jul-2007, 02:09pm

I have a problem with the gearbox on my Spitfire 4. It jumps out of 3rd gear (only). It seems that when I push it back in, it stays but I am not conscious that the lever has travelled any further. I took the top off this w/e and checked that the spring loaded balls were holding ok. No apparent problem there. Any thoughts?

Followups :

Jumping out of gear

Posted By : Chris Lilley, 22-Jul-2007, 03:48pm

Can you get reverse ok?
- Jumping out of gear
  
  Posted By : Peter & Mick Lewis, 22-Jul-2007, 05:10pm
  
  worth a check make sure the bolt thro the fork under the gear lever spherical is not to long or wrong way round and fouling on the remote casing when in gear, but this is normally more evident in 4th ,,pete
  - Jumping out of gear
    
    Posted By : Stewart Sloan, 22-Jul-2007, 06:06pm
    
    Thanks Pete but do not think this is the problem.
- Jumping out of gear
  
  Posted By : Stewart Sloan, 22-Jul-2007, 06:03pm
  
  All other gears no problem.
  - Jumping out of gear
    
    Posted By : Charles Bushell, 22-Jul-2007, 06:39pm
    
    When you said you "checked that the spring loaded balls were holding ok" did you mean the ones in the selector mechanism or in the synchro hubs? I think broken springs in the synchro hubs can cause this (if that's not what you meant anyway!)
    - Jumping out of gear
      
      Posted By : Stewart Sloan, 22-Jul-2007, 10:23pm
      
      I meant the ones in the selector mechanism. Would not plan to go any deeper!
      - Jumping out of gear
        
        Posted By : Philip Brammer, 22-Jul-2007, 11:26pm
        
        I suspect this is a sychromesh problem. Either a stripdown or exchange to cure I'm afraid
        
        Jumping out of gear
        
        Posted By : Chris Taylor, 23-Jul-2007, 01:48am
        
        I would tend to agree that this is likely to be a problem with the synchro hub, but it is just worth checking out for any play in the remote linkage bushes. Also just possible the problem is wear on the selector fork, which is not always pushing the synchro hub far enough back to fully engage the detent. These can be examined by unbolting the housing off the top of the gearbox, but I'm pretty sure these are not available new anymore. They are a pain to fit to the selector rods, so the simplest solution, if that is the problem, is to swap the whole selector housing from another gearbox.
        If your gearbox is an original 3-synchro box, any Herald gearbox selector unit is a straight swap, just change the actual gearlever for the more cranked Spitfire one. (If you have overdrive though, be careful which bits you swap so that you have the longer shaft accommodating the overdrive inhibitor switch cam).