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        General >> Give/Need advice to/from others >> overdrive 
        
(Message started by: rich1 on Feb 28th, 2009, 9:23pm)
Title: overdrive
Post by rich1 on Feb 28th, 2009, 9:23pm
settle an arguement for me , the overdrive should be used for motorway driving . yes or no? and what does it actually do for the car?
Title: Re: overdrive
Post by gozz on Feb 28th, 2009, 9:50pm
Rich.
If you mean overdrive on your Scorp it engages automatically anyway,the button on the side of the gear selector is to temporarily disengage it.On a manual box you can choose whether or not to select it.The purpose of it is of course to give better fuel economy,but a lusty engine is needed to obtain this,there would be little point in fitting overdrive to a low output engine unless the diff ratio were lowered to match.
                      Are yer wimme?
                             GOZZ.
Title: Re: overdrive
Post by gost on Feb 28th, 2009, 10:16pm
Gozz, even at this time of night you are a wealth of wisdom ::) As for me, to much wine, not a clue what u all talking about ;D
Title: Re: overdrive
Post by gozz on Feb 28th, 2009, 10:23pm
gost.
I understand me old mate,but only when a suitable noggin has been imbibed,or if you happen to be a Roman Candle,a modest libation has been taken  ;D.
      In other words ' yesh oi no watcher mean '  ;)
                                          GOZZ.
Title: Re: overdrive
Post by big_timer on Mar 1st, 2009, 12:20am
overdrive on a manual?how do i engage that gozz is there a special button or something like that?
Title: Re: overdrive
Post by 5stud on Mar 1st, 2009, 12:48am
overdrive brings back memoreys.mk2 vanden plas 3 speed plus overdrive big leaver you pulled from under the dash to engage .even had a distreutor on the gearbox to disengage when you sloed down .probiley last ford  to use proper overdrive mk 3 trasit
Title: Re: overdrive
Post by Jonnycab on Mar 1st, 2009, 1:48am

on 02/28/09 at 21:23:24, rich1 wrote:
settle an arguement for me , the overdrive should be used for motorway driving . yes or no? and what does it actually do for the car?


In laymans terms.....overdrive on the Scorpio auto is the forth gear  ;)....... & as Gozz states, is for economy at high speed  :)

Also, as far as I'm aware, MT75 manual gearboxes don't have this option  :)
Title: Re: overdrive
Post by Simmo on Mar 1st, 2009, 7:45am
In effect fifth gear is a form of overdrive. In 'days of yor' when JC was but a twinkle in his dads eye  ;D  cars mostly had just four gears and a lack of motorways meant that high speed cruising was unusual. As both cars and roads improved cars were equipped with a switch which enabled the driver to,in effect, select a higher gear when the road conditions allowed thus lowering the engine revs and increasing economy.  Snoopy, Gozz and  Gost will no doubt remember such innovations ! :D ;D and cars with only three gears and wipers working off a vacuum which slowed down as you went up hill!!.

Highlander.....before you reply remember us 'oldies' are watching you!! ;D

A more detailed explanation,and history is HERE (http://en.wikipedia.org/wiki/Overdrive_(mechanics)) Rich. :)
Title: Re: overdrive
Post by Scorpio_Mike on Mar 1st, 2009, 8:26am
I remember my Sunbeam Rapier fastback - had O/D on 3rd & 4th - effectively a 6-speed gearbox  - WOW  :o

On the Scorpio auto box, I thought they were 4-spd + O/D  ???
I'm sure I've counted the gearchanges going up and 4th comes in at around 40 ~ 42 mph, O/D comes in at around 50 mph.
Can someone tell me if this is right or have I imagined the extra change  :-/
Title: Re: overdrive
Post by big_timer on Mar 1st, 2009, 2:58pm
glad i brought back some memories
Title: Re: overdrive
Post by scorpio_man on Mar 1st, 2009, 3:03pm

on 03/01/09 at 08:26:32, Scorpio_Mike wrote:
I remember my Sunbeam Rapier fastback - had O/D on 3rd & 4th - effectively a 6-speed gearbox  - WOW  :o

On the Scorpio auto box, I thought they were 4-spd + O/D  ???
I'm sure I've counted the gearchanges going up and 4th comes in at around 40 ~ 42 mph, O/D comes in at around 50 mph.
Can someone tell me if this is right or have I imagined the extra change  :-/



hi there

what you are getting is the t/c locking up.

hth
Title: Re: overdrive
Post by gozz on Mar 1st, 2009, 8:04pm
Yes,as Simmo says top gear in most modern manual boxes is overdriven,thus negating the need for a seperate overdrive unit that was bolted oto the back of the main box,and operated on 3rd and 4th only,having a seperate switch,which on later vehicles was in the top of the gear knob.
                                             GOZZ.
Title: Re: overdrive
Post by rich1 on Mar 1st, 2009, 10:57pm
so if your driving around town should you switch it off??
Title: Re: overdrive
Post by Tompion on Mar 1st, 2009, 11:31pm
With regard to driving under power I don’t think it matters, but with your foot off the throttle it gives engine braking.
With some long slight declines I commonly use, turning off overdrive is just enough to keep the speed down to 30mph without using the brakes.
Title: Re: overdrive
Post by mr._floppy on Mar 2nd, 2009, 2:06am

In simple terms,  in a  5 speed manual boxes,  when you're in 4th gear  the engine is  turning  the same speed as  the  propshaft .

In  5th gear  the  engine  is  turning  slightly slower than the propshaft which means  lower revs, higher speed  and   better fuel economy  but  less torque and less  puff  when you come to an  incline  and you have to change  to 4th or 3rd.

Automatics  have  the  same  system except  less  gears,  4th  being  the Overdrive.
Title: Re: overdrive
Post by Highlander on Mar 3rd, 2009, 9:25pm

on 03/01/09 at 22:57:29, rich1 wrote:
so if your driving around town should you switch it off??

Its just a higher gear Rich, if you press the button on the shifter and the green OD light shows on the dash then you have disabled top gear and it will only use 1st 2nd and 3rd.

I only really ever use it for maximum acceleration :)

switching it off at under 50mph will not make any difference.
Title: Re: overdrive
Post by and11 on Mar 17th, 2009, 12:26pm

on 03/03/09 at 21:25:59, Highlander wrote:
Its just a higher gear Rich, if you press the button on the shifter and the green OD light shows on the dash then you have disabled top gear and it will only use 1st 2nd and 3rd.

I only really ever use it for maximum acceleration :)

switching it off at under 50mph will not make any difference.

Surely that's what the S button is for?
Title: Re: overdrive
Post by mindofitsown on Mar 17th, 2009, 1:47pm

on 03/17/09 at 12:26:58, and11 wrote:
Surely that's what the S button is for?


Hi "and11",
Actually no, the 'S' button causes the electronics to upshift the autobox at  higher speeds (i.e. later) than normal thus increasing the time for which higher torque is available during acceleration and it affects all gears. The overdrive button simply engages/disengages top gear but does not affect the lower gear shift speeds.
HTH, regards.
Title: Re: overdrive
Post by Highlander on Mar 17th, 2009, 8:05pm
Sorry maybe i should have explained in a bit more depth.

For maximum acceleration depress the OD button so that the green light shows on the dash eg top gear is disabled (you can still hit 100 in 3rd easily) ;)

Pressing the S button will as stated above hold the gearchange until 6000 rpm meaning the engine can produce maximum torque.

So pressing both OD and S will give the  fastest acceleration possible although the OD being disabled will only make a difference once you have reached the point where top gear would normally engage.

makes quite a difference ;)
Title: Re: overdrive
Post by and11 on Mar 19th, 2009, 8:52pm
Interesting, must try that next time i get a chance ;D


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