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02/09/2002 11:39:48   bill rawles   Can any-one advise on this please? My speedo works fine when the car is accelerating or on partial throttle but when I am on the over-run or freewheeling I loose part of the drive so the speedo drops by about 2/3rds of whatever speed I am doing at the time (60mph will indicate about 40). As soon as I accelerate again it bounces back to where it should be.

I see in the manual that the speedo drive can be adjusted with shims but before I start dismantling does this sound like what I need to be doing. Do I need to add or remove shims? Could the pinion gear be worn so that it is slipping?

My doomsday scenario is that the gearbox is badly worn so the main/lay shaft is moving on its bearings and dissengaging the speedo drive - some-one please tell me that is too pessimistic!

02/09/2002 14:34:27   Steve B   Hi Bill,

If your gearbox bearings are worn then another sign to look for is a pulsing of the speedo needle when accelerating. I believe this is a sign of worn differential bearings, but all cars do it a bit.

Sounds like your next move might be to remove the speedo drive from the gearbox and inspect it but before you do check that the square ends of the speedo cable are in fact square and that the holes they fit into are also square. Slipping can occur here otherwise.

Another check is to undo to clock end of the cable and whilst driving along grip the end and see how strong the drive is. This will provoke slipping at the gearbox end if there is any.

Good luck.  
02/09/2002 18:31:17   Alec   I have also found that different speedo heads suffer more/less from this, probably due to the springs getting weak. It may be worth trying another head if you have one to see how bad it is then.  

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