pewe
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| posted on 13/3/16 at 05:36 PM |
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Overdrive??
Reading an article in a classic magazine prompted me to ask if anyone has fitted an overdrive?
If so what, how and how much?
The reason is the hairdressers is low enough geared to provide sparkling acceleration but in 5th (top) gear is only giving 19mph/000 revs.
Whilst that's acceptable in most situations doing long motorway drives and track days on higher speed circuits means running out of revs etc.
Fitting a 6 speed box or different diff isn't really an option so any thoughts gratefully received.
BTW it has a PPF rail (think aluminium girder) between the back of the box and the diff so lateral space around the propshaft may be an issue
TIA, Pewe10 
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gremlin1234
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| posted on 13/3/16 at 05:59 PM |
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first question is what gearbox do you currently have?
many of the triumph models offered overdrive, using laycock units, but 5th and 6 gears generally replaced them in normal use.
maybe you could just go to bigger wheels and tyres?
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cliftyhanger
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| posted on 13/3/16 at 06:06 PM |
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Used by volvo and many others too. But not really a practical solution as fitting is not a boly on job by any stretch of the imagination.
However, many years ago I did hear of a landrover conversion that may be bolt on. Don't expect it to be a cheap exercise though.
Why no 6 speed or higher ratio diff?
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theconrodkid
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| posted on 13/3/16 at 06:06 PM |
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Easiest way would be fitting a higher ratio diff,(not what you want to hear),i read something about a hyundai one being higher ratio and a straight
swap.
O/D.s are quite big and i cant se there being space for one.
who cares who wins
pass the pork pies
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gremlin1234
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| posted on 13/3/16 at 06:16 PM |
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quote:
Originally posted by cliftyhanger
Used by volvo and many others too. But not really a practical solution as fitting is not a boly on job by any stretch of the imagination.
However, many years ago I did hear of a landrover conversion that may be bolt on. Don't expect it to be a cheap exercise though.
Why no 6 speed or higher ratio diff?
the landrover one used the aux drive coming out, and back in, not sure how, but powered by fairey
units
see
http://www.syncrogearboxes.com/fitting-a-fairey-overdrive-to-a-land-rover-series-3/
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pewe
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| posted on 13/3/16 at 06:32 PM |
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Thanks guys.
It was actually a Landie one featured in the article I was reading which seemed to be a straight bolt-on job.
Bigger wheels not really an option IMO they'll look out of place on a Mk1 Eunos (already 15" v 14" originals).
Six speed box from MX5 1.8 ends up with similar ratios as current.
Daihatsu diff interesting Conrod but only if they do Torsen LSD's or similar.
Space as we both know likely to be limited by the PPF....
Cheers, Pewe10
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britishtrident
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| posted on 13/3/16 at 06:35 PM |
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Overdrives offer less of an increase in gearing than a 5th gear, but they do have advantages.
Personal choice would be the semi-close ratio version of the Rootes gearbox also used in the Jensen Healey
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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emwmarine
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| posted on 13/3/16 at 07:07 PM |
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I've got one on my GT6. It works on 3rd and 4th.
A bit complex but they work very well. Especially useful when accelerating in 3rd and you flick the switch and you get an immediate gear that's
like 3.75. Very good for overtaking.
Building a Dax Rush.
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Doctor Derek Doctors
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| posted on 13/3/16 at 08:18 PM |
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The landie ones are simple bolt on devices because they have a transfer box. You bolt it on the back, and it replaces the gear that drives onto the
transfer box. (Very simplified explanation )
It's a bit more difficult fitting then inline with e normal rwd gearbox.
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britishtrident
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| posted on 13/3/16 at 08:19 PM |
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The crude Landrover Fairy unit is completely different in operation from passenger car overdrive units.
The Laycock-de Normanville commonly fitted overdrives on British tintops were fairly simple planetary gearboxes similar in principal to a.
Conventional automatic transmission.
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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sprintB+
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| posted on 15/3/16 at 11:24 AM |
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My B+ has the overdrive on the gearbox linked to the Dolomite sprint engine. Very heavy gearbox and overdrive unit. However in the days when it was
used in anger on hillclimbs and sprints the "extra" gears were very welcome. Even now to cruise on motorways in overdrive top is quite
pleasurable, and it makes it economical if I can resist the loud pedal 
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