Converting a 4 speed gearbox to a 5 speed (1800)
Moderators: ClaytonSpeed, balmy
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Converting a 4 speed gearbox to a 5 speed (1800)
Can it be done with ease; Upgrading the box?
Or is there a quick and simple answer to lowering rpm for long halls on the motorway?
Thanks
Or is there a quick and simple answer to lowering rpm for long halls on the motorway?
Thanks
Re: Converting a 4 speed gearbox to a 5 speed (1800)
5 speed or 4 speed with overdrive can be done but neither are quick, cheap or particularly easy. Most require making the tunnel bigger ( higher )
A diff change can work - stick a 3.27 in for more relaxed motorway work if you can find one.
A diff change can work - stick a 3.27 in for more relaxed motorway work if you can find one.
1974 Marina Tc Coupe - 1950CC
1982 Morris Ital HL Estate - 7600 miles from new
1992 Lada Niva Cossack - brilliant
2008 Ducati 1098R TB21 LE 200bhp/99lb/ft of a monster on two wheels. All from 1198cc
1998 Laverda 750 Formula-rare
1997 Ducati 916 Senna - Awesome
!974 Honda CD175-awaiting resto - now stripped
1982 Morris Ital HL Estate - 7600 miles from new
1992 Lada Niva Cossack - brilliant
2008 Ducati 1098R TB21 LE 200bhp/99lb/ft of a monster on two wheels. All from 1198cc
1998 Laverda 750 Formula-rare
1997 Ducati 916 Senna - Awesome
!974 Honda CD175-awaiting resto - now stripped
- locost_bryan
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Re: Converting a 4 speed gearbox to a 5 speed (1800)
Read this thread MORRIS MARINA/ITAL REAR AXLE/DIFFERENTIAL & OPTIONS for very detailed diff options, and this thread 1700 O Series Gearbox Options for gearbox options.
Bryan
Auckland NZ
1972 Morris Marina 1750 TC Coupe "Ozzy"
Auckland NZ
1972 Morris Marina 1750 TC Coupe "Ozzy"
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Re: Converting a 4 speed gearbox to a 5 speed (1800)
So I see its either a dip swap or a gear box swap then
So not an easy fix for a long hall on the motorway after all
So not an easy fix for a long hall on the motorway after all
- locost_bryan
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Re: Converting a 4 speed gearbox to a 5 speed (1800)
BL made the trans tunnel as small as possible to maximise the amount of interior space, so it limits what you can fit in there.
Bryan
Auckland NZ
1972 Morris Marina 1750 TC Coupe "Ozzy"
Auckland NZ
1972 Morris Marina 1750 TC Coupe "Ozzy"
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Re: Converting a 4 speed gearbox to a 5 speed (1800)
I dont know who or what BL is or what a trans tunnel is eitherlocost_bryan wrote: ↑Wed Oct 26, 2022 12:38 am BL made the trans tunnel as small as possible to maximise the amount of interior space, so it limits what you can fit in there.
Re: Converting a 4 speed gearbox to a 5 speed (1800)
BL - British Leyland, the parent company of Morris at the time the Marina was designed and built.
Trans tunnel- Transmission Tunnel, fairly self explanatory, it's the bump between the seats to give clearance for the gearbox and propshaft. It's unusually small on a Marina as Bryan has said, good for interior space, bad for fitting bigger gearboxes.
Trans tunnel- Transmission Tunnel, fairly self explanatory, it's the bump between the seats to give clearance for the gearbox and propshaft. It's unusually small on a Marina as Bryan has said, good for interior space, bad for fitting bigger gearboxes.
Matt
1974 1973 Tundra Black Tulip 1800 SDL TC Estate "Mud"- slowly slowly coming together.
1972 White 1800 DL Saloon- Better than it looks, but it looks awful...
1974 1973 Tundra Black Tulip 1800 SDL TC Estate "Mud"- slowly slowly coming together.
1972 White 1800 DL Saloon- Better than it looks, but it looks awful...
- locost_bryan
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Re: Converting a 4 speed gearbox to a 5 speed (1800)
As Balmy said, the only easy option is to fit a taller 3.27 diff. You'll also need to fit the correct speedo drive gear in the gearbox, or else the speedo will read wrong. I think the differential option thread says which one you need. Rimmer Bros sell the 3.27 crownwheel and pinion for £384.00 (inc VAT) https://rimmerbros.com/Item--i-159803
Bryan
Auckland NZ
1972 Morris Marina 1750 TC Coupe "Ozzy"
Auckland NZ
1972 Morris Marina 1750 TC Coupe "Ozzy"
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Re: Converting a 4 speed gearbox to a 5 speed (1800)
So its going to be a lot of money and work. I think its best to walk away from this as soon as.....
Re: Converting a 4 speed gearbox to a 5 speed (1800)
The last 3.27 diff I picked up cost £70 I think.
Frequent some dolomite or early GT6 FB pages!
Frequent some dolomite or early GT6 FB pages!
1974 Marina Tc Coupe - 1950CC
1982 Morris Ital HL Estate - 7600 miles from new
1992 Lada Niva Cossack - brilliant
2008 Ducati 1098R TB21 LE 200bhp/99lb/ft of a monster on two wheels. All from 1198cc
1998 Laverda 750 Formula-rare
1997 Ducati 916 Senna - Awesome
!974 Honda CD175-awaiting resto - now stripped
1982 Morris Ital HL Estate - 7600 miles from new
1992 Lada Niva Cossack - brilliant
2008 Ducati 1098R TB21 LE 200bhp/99lb/ft of a monster on two wheels. All from 1198cc
1998 Laverda 750 Formula-rare
1997 Ducati 916 Senna - Awesome
!974 Honda CD175-awaiting resto - now stripped
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- Joined: Sat Oct 22, 2022 10:39 pm
Re: Converting a 4 speed gearbox to a 5 speed (1800)
Was that new or used?
Was it a complete diff shaft or an add on?
Did it up the ratio on top 4th gear and what about first? or was the diff a separate item and a separate gear its self?
Converting a 4 speed gearbox to a 5 speed (1800)
Used. Claimed to have done only 27k miles and seems in good nick.
Complete diff. It ups the ratio in every gear. First is fine even when pulling away but then my car has a little more torque than a standard 1800.
Complete diff. It ups the ratio in every gear. First is fine even when pulling away but then my car has a little more torque than a standard 1800.
1974 Marina Tc Coupe - 1950CC
1982 Morris Ital HL Estate - 7600 miles from new
1992 Lada Niva Cossack - brilliant
2008 Ducati 1098R TB21 LE 200bhp/99lb/ft of a monster on two wheels. All from 1198cc
1998 Laverda 750 Formula-rare
1997 Ducati 916 Senna - Awesome
!974 Honda CD175-awaiting resto - now stripped
1982 Morris Ital HL Estate - 7600 miles from new
1992 Lada Niva Cossack - brilliant
2008 Ducati 1098R TB21 LE 200bhp/99lb/ft of a monster on two wheels. All from 1198cc
1998 Laverda 750 Formula-rare
1997 Ducati 916 Senna - Awesome
!974 Honda CD175-awaiting resto - now stripped
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- Joined: Sat Oct 22, 2022 10:39 pm
Re: Converting a 4 speed gearbox to a 5 speed (1800)
But did it up the gear ratio where it felt like a whole gear? So first would feel like second and 4th would feel like 5th
Re: Converting a 4 speed gearbox to a 5 speed (1800)
No. Nothing like. It’s only a 11% difference but for me it makes enough difference for covering large distances ( 1000 miles done in 24 hours last yearThe Breaker wrote:But did it up the gear ratio where it felt like a whole gear? So first would feel like second and 4th would feel like 5th

I’ve driven 5 speed converted Marinas.
Mine sites at exactly the same revs at 60mph as those in 5th as mine in 4th.
1974 Marina Tc Coupe - 1950CC
1982 Morris Ital HL Estate - 7600 miles from new
1992 Lada Niva Cossack - brilliant
2008 Ducati 1098R TB21 LE 200bhp/99lb/ft of a monster on two wheels. All from 1198cc
1998 Laverda 750 Formula-rare
1997 Ducati 916 Senna - Awesome
!974 Honda CD175-awaiting resto - now stripped
1982 Morris Ital HL Estate - 7600 miles from new
1992 Lada Niva Cossack - brilliant
2008 Ducati 1098R TB21 LE 200bhp/99lb/ft of a monster on two wheels. All from 1198cc
1998 Laverda 750 Formula-rare
1997 Ducati 916 Senna - Awesome
!974 Honda CD175-awaiting resto - now stripped
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- Posts: 17
- Joined: Sat Oct 22, 2022 10:39 pm