What did the overdrive switch in an old Volvo do?
Discussion
My dad had some kind of Volvo sedan/coupé with four (possibly five) gears and an overdrive switch back in the mid-80s. The gears I understood even back then, probably because I had the massive Technic Lego chassis set, but the overdrive was literally a switch on top of the gear lever.
What did it do to the engine/gearing, and what physically did that switch do, was it purely electronic or did it shift some gearing around somewhere?
It was the first car we ever had with a sunroof, and probably the last now I think about it. Tiny boot though.
What did it do to the engine/gearing, and what physically did that switch do, was it purely electronic or did it shift some gearing around somewhere?
It was the first car we ever had with a sunroof, and probably the last now I think about it. Tiny boot though.
I presume it is the same as overdrive on other cars of the era. It had an overdrive unit on tje back of tje gearbox which has two speed gears in it.
With overdrive engaged itlowered the gear ratios. It was not always active in all gears, for instance on my old MGB the overdrive only worked on 3rd and 4th gears.
Edit: lowered should be raised!
With overdrive engaged it
Edit: lowered should be raised!
Edited by Scrump on Thursday 28th March 16:14
Scrump said:
I presume it is the same as overdrive on other cars of the era. It had an overdrive unit on tje back of tje gearbox which has two speed gears in it.
With overdrive engaged it lowered the gear ratios. It was not always active in all gears, for instance on my old MGB the overdrive only worked on 3rd and 4th gears.
Raised the gearing you mean.With overdrive engaged it lowered the gear ratios. It was not always active in all gears, for instance on my old MGB the overdrive only worked on 3rd and 4th gears.
It would have had a 4 speed box, like most cars of that era, and it would have been like moving up a gear... engaging 5th... lowering the rpm/mph and allowing quieter and more fuel-efficient cruising.
The switch electrically pulled a solenoid which operated the small planetary 'gearbox' bolted to the back of the main gearbox.
TwinKam said:
Raised the gearing you mean.
It would have had a 4 speed box, like most cars of that era, and it would have been like moving up a gear... engaging 5th... lowering the rpm/mph and allowing quieter and more fuel-efficient cruising.
The switch electrically pulled a solenoid which operated the small planetary 'gearbox' bolted to the back of the main gearbox.
Yes, raised. I was too busy dealing the Dubai spam and must have been distracted It would have had a 4 speed box, like most cars of that era, and it would have been like moving up a gear... engaging 5th... lowering the rpm/mph and allowing quieter and more fuel-efficient cruising.
The switch electrically pulled a solenoid which operated the small planetary 'gearbox' bolted to the back of the main gearbox.
ScotHill said:
My dad had some kind of Volvo sedan/coupé with four (possibly five) gears and an overdrive switch back in the mid-80s. The gears I understood even back then, probably because I had the massive Technic Lego chassis set, but the overdrive was literally a switch on top of the gear lever.
What did it do to the engine/gearing, and what physically did that switch do, was it purely electronic or did it shift some gearing around somewhere?
It was the first car we ever had with a sunroof, and probably the last now I think about it. Tiny boot though.
I had a 122S way back, great car way ahead of its time, I think the switch operated a solenoid which switched a pump to operate the gears without dipping the clutch.What did it do to the engine/gearing, and what physically did that switch do, was it purely electronic or did it shift some gearing around somewhere?
It was the first car we ever had with a sunroof, and probably the last now I think about it. Tiny boot though.
One of my better buys, wonder if it is still on the road? Take you to the moon and back
Overdrive was very common until the 1970s, You found it on Jaguars, Rovers, Triumphs, Volvos, etc, etc. My Vitesse had overdrive on 3rd and 4th, as had my Dolomite Sprint. TRs up to the 4a (I think) had it on 2nd as well. I remember a friend who had a V6 LWB Transit rally barge which had overdrive on 4th. Normally it was operated by a column operated switch, although a gearknob operated switch was the norm later. No clutch operation required. The attached is a Jaguar/Daimler one.
My F150 Lightning has an OD with the button on the end of the gearshift stalk. It does feel a bit antiquated but it works fine, I just treat it as top gear, it’ll engine brake when you disengage when slowing down. It wakes you up if you forget to disengage when going for an overtake as it’ll drop 2 gears at once.
I recently changed a clutch in a mk1 transit that had the switch for the OD on the dash. After the job was done I took it out for a test drive with the owner. He’d recently bought it and his jaw dropped when I hit the switch at cruising speed, turns out he thought the switch was for some old auxiliary lights or something. He’d just driven the thing hundreds of miles to take it home, all the way with it screaming.
matchmaker said:
Overdrive was very common until the 1970s, You found it on Jaguars, Rovers, Triumphs, Volvos, etc, etc. My Vitesse had overdrive on 3rd and 4th, as had my Dolomite Sprint. TRs up to the 4a (I think) had it on 2nd as well.
When I had a Dolomite Sprint it was a fairly easy mod to enable OD on second as well done by a few (not me) on the owners club forum.I used to love the OD on 3rd on a fast B road, a quick flick to 3rd for corners or overtakes.
I had an overdrive in an old mgb gt, that was the mechanical add on unit that operated when the switch was pressed.
I also had a 95 Nissan with an ‘overdrive’ but I think that was just locking out the top gear of the normal automatic gearbox unless selected. They sold a lot of them in the US where it seemed more common.
I also had a 95 Nissan with an ‘overdrive’ but I think that was just locking out the top gear of the normal automatic gearbox unless selected. They sold a lot of them in the US where it seemed more common.
ScotHill said:
My dad had some kind of Volvo sedan/coupé with four (possibly five) gears and an overdrive switch back in the mid-80s. The gears I understood even back then, probably because I had the massive Technic Lego chassis set, but the overdrive was literally a switch on top of the gear lever.
What did it do to the engine/gearing, and what physically did that switch do, was it purely electronic or did it shift some gearing around somewhere?
It was the first car we ever had with a sunroof, and probably the last now I think about it. Tiny boot though.
The overdrive is a secondary gearbox fitted behind the main one. Almost all overdrives are epicyclic like automatic gearboxes, the switch actuates a solenoid valve which engages and disengages the overdrive hydraulically. What did it do to the engine/gearing, and what physically did that switch do, was it purely electronic or did it shift some gearing around somewhere?
It was the first car we ever had with a sunroof, and probably the last now I think about it. Tiny boot though.
My first car with overdrive was a '69 Vx Ventora, my last car a '93 Volvo 940 estate.
Never thought i'd see a proper overdrive again, until i received my new Scania truck a few weeks ago, when up to speed and not pulling as such it automatically drops into, yes, overdrive.
Drops the revs from 1200rpm @ 55mph to 920rpm, the way it behaves suggests its not designed to take full engine torque because soon as the slightest incline (when fully loaded)is sensed it drops back into 12th immediately, when empty it spends a lot more time in OD.
You can manually select OD but if the vehicle doesn't like it will revert to normal gear.
Never thought i'd see a proper overdrive again, until i received my new Scania truck a few weeks ago, when up to speed and not pulling as such it automatically drops into, yes, overdrive.
Drops the revs from 1200rpm @ 55mph to 920rpm, the way it behaves suggests its not designed to take full engine torque because soon as the slightest incline (when fully loaded)is sensed it drops back into 12th immediately, when empty it spends a lot more time in OD.
You can manually select OD but if the vehicle doesn't like it will revert to normal gear.
The Volvo probably had a Laycock de Normanville (!) overdrive. See here for how it works: https://www.uniquecarsandparts.com.au/how_it_works...
John
John
JimbobVFR said:
matchmaker said:
Overdrive was very common until the 1970s, You found it on Jaguars, Rovers, Triumphs, Volvos, etc, etc. My Vitesse had overdrive on 3rd and 4th, as had my Dolomite Sprint. TRs up to the 4a (I think) had it on 2nd as well.
When I had a Dolomite Sprint it was a fairly easy mod to enable OD on second as well done by a few (not me) on the owners club forum.I used to love the OD on 3rd on a fast B road, a quick flick to 3rd for corners or overtakes.
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