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jiminox
Joined: 12 Dec 2011 Posts: 5
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Posted: Tue Dec 13, 2011 8:40 am Post subject: overdrive on a 1961 humber hawk |
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Hi, does anyone know why after driving my humber hawk for a few miles the overdrive stops working. thanks jim. |
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victor 101
Joined: 03 Apr 2009 Posts: 446 Location: East Yorkshire
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Posted: Tue Dec 13, 2011 5:22 pm Post subject: |
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Have you checked the gearbox oil level? |
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Phil - Nottingham
Joined: 01 Jan 2008 Posts: 1252 Location: Nottingham
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Posted: Tue Dec 13, 2011 7:26 pm Post subject: |
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also the filter and/or elecric connections and relays/switches _________________ Rover P2
Rover P4
Rover P5 & P5B
Land Rover S2 & S3
Morris Mini Traveller Mk2 |
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jiminox
Joined: 12 Dec 2011 Posts: 5
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Posted: Wed Dec 28, 2011 5:09 pm Post subject: |
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The gearbox oil level is fine, and so are the connections. i have not checked the filter. the over drive will stay engaged if i leave it switched on until i turn off the ignition, then it will not engage again until it has got cold. thanks for your replies. also my manual says it needs 20w 20 oil, but i cannot get hold of that grade.is there a good equivalent oil i can use . cheers jim. |
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MVPeters
Joined: 28 Aug 2008 Posts: 822 Location: Northern MA, USA
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Posted: Wed Dec 28, 2011 7:46 pm Post subject: |
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On the face of it, this sounds like low oil pressure in the O/D unit. Hard to test & harder to fix.
Fresh oil - & 20W/30 or even 20W/50 should be fine - might be a help.
If there's a Lucas 6RA relay in there somewhere, put a new one in! This was a common MGB failure point, though not really connected with temperature. _________________ Mike - MVPeters at comcast.net
2002 MINI Cooper 'S' |
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Jim.Walker
Joined: 27 Dec 2008 Posts: 1229 Location: Chesterfield
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Posted: Thu Dec 29, 2011 2:32 pm Post subject: |
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The operating solenoid will have two coils (assuming it is not Laycock). One engages the overdrive and then cuts out leaving a holding coil to keep it engaged.
Your symptoms seem to suggest a heat related electrical resistance somwhere wich prevents the engaging coil to work until things cool down. Perhaps the operating relay or the operating coil in the solenoid. But first check the operating lever adjustment to ensure it is moving through the correct arc of travel. Usually done with a dowel (twist drill shank) in the on and off position.
Jim. _________________ Quote from my late Dad:- You only need a woman and a car and you have all the problems you
are ever likely to want". Computers had not been invented then! |
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richardlw
Joined: 08 Jun 2009 Posts: 138
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Posted: Mon Jan 02, 2012 2:26 am Post subject: |
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Reference to a 20W-20 oil is a reference in motor oil SAE chart, where we should be looking at the gear oil SAE chart. a 20W-20 would be a 75W-80 gear oil, and should be a GL-3 or GL-4 for most transmissions, especially synchronized gear boxes.
You should find several brands with a 75W-80 GL-4 or GL-3 on the shelf. _________________ Richard's Cars - NEW **
Motor oil for Flat Tappet Engines
Transmission oil |
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jiminox
Joined: 12 Dec 2011 Posts: 5
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Posted: Tue Feb 28, 2012 11:51 pm Post subject: overdrive |
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thanks for all your feedback people. i am going to try them all and let you know the outcome. much appreciated. jim. |
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