[Sunbeam Talbot Email List] overdrive

[Mal Clark]

Hi Henry, I believe, it will distroy the one way clutch inside the overdrive, this clutch consists of a ramped type bearing with rollers that fit into a cage,and as descibed,it can only turn one way while in overdrive , and when reverse is selected, and the overdrive is stuck in, the clutch will be the thing that is damaged,  I have never seem this damage,myself,but thats what would happen, Mal Clark.
  From: Henry Gillard 
  To: Mal Clark ; mountclarke at gmail.com ; staowners web-site email list 
  Sent: Saturday, June 26, 2010 7:20 AM
  Subject: RE: [Sunbeam Talbot Email List] overdrive


  Mal
  What actually happens if you reverse the car with the overdrive engaged ?  What breaks ?
  From experience with my Hawk, I have reversed the car into the garage a couple of times with the overdrive engaged, and suffered no ill-effects.  Admittedly that would have been only 20 or 30 feet at a crawl, which may not be as detrimental.
   
  As an aside, it has always struck me as ridiculous that any manufacturer would sell an o/d which didn't have in interlock to prevent engagement in reverse (which apparently could damage it) while having an interlock to prevent engagement in 1,2 and 3, (which apparently wouldn't).
   
  Mind you, overdrives themselves always seemed a complex and expensive way of getting a fifth gear
   
  Ahh, this was sort of approach to engineering which led to the complete demise of British volume vehicle manufacture
   

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  From: shadow74 at bigpond.com
  To: mountclarke at gmail.com; staowners at sunbeamtalbot.info
  Date: Fri, 25 Jun 2010 13:51:09 +1000
  Subject: Re: [Sunbeam Talbot Email List] overdrive


  Hi Martin,the overdrive works by means of oil pressure,that is produce by the oil pump in the overdrive,when you operate the overdrive switch it allows this oil pressure to activate two hydrolic pistons that push against two plates that are connected to the cone clutch the piston pressure overcomes a series of return springs,to push the cone clutch to it overdrive position,When the switch is returned to the off position the pressure is released and the return springs pull the clutch back from the overdrive position. if its not disengaging,either the pressure is not being released, or the pistons are stuck, I cant imagine a broken spring as there are so many that work the clutch. You will know when removed.Mal Clark.
    ----- Original Message ----- 
    From: martin clarke 
    To: staowners at sunbeamtalbot.info 
    Sent: Friday, June 25, 2010 11:25 AM
    Subject: [Sunbeam Talbot Email List] overdrive


    Dear Members, 
              Has anyone been through the overdrive stuck in overdrive problem. The handbook says that serious damage occurs if the car is reversed while stuck in overdrive. My MKIII saloon has just clocked 2,980 km (approx 1800 miles) in a return trip to Mount Gambier, just across the border in South Australia for the National rally. It was a good roll up, and an enthusiastic atmosphere, with Mal Clarke's handywork impressing all and sundry. Roland Thompson covered approximately 1500km more than I did, in bringing his Fine alpine, and his MKIII drophead from Queensland. 
              Needless to say the overdrive first became intermittent, and then finally decided to lock in about 1,200km from home. A quick crawl under revealed that something (probably broken spring) was preventing the lever from dropping to the off position. Attempts to move it manually failed. Naturally the only choice was to drive home, and inevitably an occasion arose where I could not avoid reversing.
              Fortunately I have a serviceable unit to put in, but I would be grateful if anyone can forewarn me of what I can expect to find when I pull the damaged unit apart.
    Regards,
    Martin Clarke
    Blue Mountains
    Australia

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