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johnc
United Kingdom
212 Posts |
 Posted - 20 Mar 2013 : 19:32:53
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Hi all,
This may seem like a really dumb question but I'll ask anyway.
I'm about to recomission my Series IV after a very,very lengthy restoration and have been wondering about the correct way to engage/disengage overdrive.Over forty years ago I had a SIIIA with O/D and the diff shed a tooth and I am wondering if it was a result of stress caused by mis-use of the O/D.
Any pointers as to proper use would be appreciated.
johnc |
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UMU
United Kingdom
343 Posts |
Posted - 20 Mar 2013 : 20:27:36
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Id say the overdrive works best and smoothest when under acceleration and tends to give a harsher shift when revs are up but your off the throttle.
When slowing beyond 3rd gear, shifting into 2nd will knock the overdrive off, which is better than taking it off then going into 2nd.
Also remember not to use gearbox oil, but instead 20/50 - which really improves things
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turbinecol
United Kingdom
85 Posts |
Posted - 21 Mar 2013 : 08:34:31
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for the disengagement with closed/trailing throttle, it sometimes help with a D-type to de-clutch if you want to minimise jolting. Otherwise you can try and blip the throttle to help smooth things.
This is where the J type has a big advantage, much smoother changes for the later Arrow owners. |
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JPSH120
United Kingdom
1183 Posts |
Posted - 21 Mar 2013 : 08:47:37
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I tend to use the clutch for downshifts but when accelerating just lift off the throttle slightly when I engage the OD.
Or should I say this is what I used to do in the days when the car was on the road!!
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johnc
United Kingdom
212 Posts |
Posted - 21 Mar 2013 : 10:15:36
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Thanks for that chaps,
I've filled up with the correct oil and will adopt your suggestions which shall be kinder to the transmission than when,as an eighteen yearold,I probably was a little too agressive with it in my quest for speed 
john |
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bigt80
United Kingdom
1052 Posts |
Posted - 23 Mar 2013 : 17:15:58
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Yes, definitely dip the clutch on down-changes. I found little difference on up-changes whether flat out or lifting throttle slightly; changes were always smooth on my early 'D' type box.
Certainly a very useful feature the o/drive |
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vintageman
United Kingdom
19 Posts |
Posted - 24 Mar 2013 : 18:21:04
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I quote from the owner's handbook
"It is not necessary to move the clutch pedal when making these changes, which should be carried out with the accelerator pedal depressed.
It is generally advisable to disengage the overdrive switch before changing from third to second gear, asthis will ensure that the transmission is not subject to heavy loads due to by-passing direct third gear"
I have a spare series III handbook if any body wants one - £12 + postage say £14
David
http://vintageman.zenfolio.com/
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bigt80
United Kingdom
1052 Posts |
Posted - 25 Mar 2013 : 11:06:53
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Indeed, for Series cars as they did not have the auto disengage switch. I think their reference to strain on transmission is because of going too fast in o/d 3rd and then going straight into 2nd
Of course Fastbacks have that auto disengage switch so that when you move the leaver across the 3rd/2nd gate it comes out of 0/drive as already mentioned.
On Series cars - although I never had one with overdrive - you can stay in overdrive even if you've come to a standstill: then when you go up through the box you'll still be o/d 3rd or 4th. Then there's the greater danger of putting it in reverse with o/d still engaged which will cause real problems.
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AlanM
Canada
11 Posts |
Posted - 20 Jun 2013 : 02:48:42
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Hi,
I always just depress the clutch when putting it in or taking it out of overdrive, just like I would shifting into or out of a regular gear. I'll give it a try without whilst engaging overdrive next time and see how it goes.
Thanks,
Alan
1962 Sunbeam Rapier Series IIIA Convertible |
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sunalp2
Australia
10 Posts |
Posted - 26 Jun 2013 : 09:06:18
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I always use the clutch too when engaging.
You must not disengage when coasting or you will glaze the linings in the overdrive, and it will eventually start to slip.
You can disengage the overdrive under power, as in going up a hill.
1962 Series II Alpine
1957 Series I Rapier |
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grumpy1
United Kingdom
34 Posts |
Posted - 17 Jul 2013 : 16:26:04
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| Interesting views on this. I have been motoring with o/drive cars for around 48 years and have always dipped the clutch when disengaging o/d to take the strain off the unit. I bought my Raoier off it's original first owner, who had an o/drive problem under warranty, so they sent out a Laycock Engineer to his home to fix the issue. He was advised by the Engineer to NEVER disengage o/d without dipping the clutch if you want the unit to be reliable for a long life. |
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janmarine3
South Africa
286 Posts |
Posted - 19 Jul 2013 : 06:32:29
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Rootes cars don't like not being at operating temperature.
I almost always use the clutch when engaging o/drive in town , much smoother and no strain. At higher speeds uphill on the open road changes can be done without using the clutch , a pleasure and extremely smooth and instant.
I forget now and again to throw the switch back and the gearbox takes quite a knock when changing from second gear to third o/d , and some slight slipping results as well, which can't be good. |
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Topic |
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Using overdrive
