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Co1



Member Since: 19 Aug 2018
Location: North Yorkshire
Posts: 3681
United Kingdom 2013 Defender 90 Puma 2.2 HT Loire Blue
Transfer box ratio change and fuel consumption.
I’m pondering a change of transfer box ratio and was thinking about whether it would have an impact on fuel economy. If I am driving at 60mph with a ratio that means I’m revving at 10% lower than standard half of me thinks that the engine isn’t working as hard to maintain the speed. The other half of me thinks I’m moving the same mass, at the same speed, through the same wind resistance, so the energy required to do so and therefore the fuel consumption should stay the same.

Discuss!!

Last edited by Co1 on 18th Apr 2022 5:26am. Edited 1 time in total
Post #949655 17th Apr 2022 3:52pm
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BaronDefenders



Member Since: 28 Jun 2019
Location: London/Cotswolds
Posts: 896
United Kingdom 2004 Defender 90 Td5 CSW Santorini Black
I’ve gone between 1.4, 1.2, and now 1.3 ratios.

The ratio, I’ve found, never made a significant real world impact on mpg. However, it has made a noticeable difference on the drive.

1.2 was great for motorway cruising, but made 1st gear too high. 1.4 was pokey but too revvy at 70mph.

I’ve settled for 1.3 as a happy medium, and I’m soon getting an R380 with V8 5th gear.

The biggest mpg changer has been tyres. Fat tyres and mpg aren’t friends Laughing Charlie

1949 Series 1 80 (SOLD)
2002 Td5 90 (SOLD)
2008 Freelander 2 (SOLD)

1958 Series 2 88 Pastel Green (2019 LR Legends Best Restored)
1983 V8 110 Limestone (Previously owned by Tom Sheppard MBE)
2004 Td5 90 Santorini Black (Td5INSIDE Powered & Rebuilt by CSK)
2012 Puma 110 Zermatt Silver (Overlanding Build)

Instagram: @BaronDefenders
Post #949659 17th Apr 2022 4:54pm
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Dinnu



Member Since: 24 Dec 2019
Location: Lija
Posts: 3422
Malta 2012 Defender 90 Puma 2.2 CSW Santorini Black
Hi Col, the puma already have 1.2 ratio, which is higher than Td5 and earlier which had 1.4.

Going for a higher ratio, like 1.1 or 1 I think you will end up using 6th less, or trying to push it harder against more wind resistance. 1988 90 Hard Top, 19J Diesel Turbo, Shire Blue - Restoration ongoing
2012 90 CSW, 2.2TDCI, Santorini Black
Post #949668 17th Apr 2022 6:14pm
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Pacha



Member Since: 23 Feb 2020
Location: North Yorkshire
Posts: 772
United Kingdom 2008 Defender 90 Puma 2.4 HT Stornoway Grey
At 60mph in top gear it's around 2000 ish RPM - not worth the effort or expense? Rgds.

Chris
Post #949685 17th Apr 2022 7:24pm
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markb110



Member Since: 22 May 2010
Location: Guildford
Posts: 2644
England 2002 Defender 90 Td5 HT Epsom Green
Best not mention the um novelty of sitting comfortably at 90mph at just less than 3,000 rpm with a two inch lift, muds, winch and a roll cage............ Whistle

How ever at £1.80 a litre and most of last week when we had no diesel locally.....the above is a thing of the past... Laughing

Probably for the best.. Rolling with laughter
Post #949690 17th Apr 2022 8:44pm
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ickle



Member Since: 22 Jul 2010
Location: South Vendee
Posts: 1786
France 2008 Defender 110 Puma 2.4 CSW Alpine White
Fit a taller profile set of tyres, same result, much easier to go back if it doesn't suit.

Only drawback is SWMBO is a little vertically challenged and struggles with the extra step up.
Post #949730 18th Apr 2022 11:46am
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Dinnu



Member Since: 24 Dec 2019
Location: Lija
Posts: 3422
Malta 2012 Defender 90 Puma 2.2 CSW Santorini Black
I was actually wondering if a 1.4 ratio is more practical for me, given the short local roads, no motorway cruising is possible.
I personally find 1st too low on the MT82 , but 2nd too high, and never use 6th.
Another plus is that the 1.4 has the larger gear teeth. Probably low ratio would not be needed anymore, as 1st would become even lower. 1988 90 Hard Top, 19J Diesel Turbo, Shire Blue - Restoration ongoing
2012 90 CSW, 2.2TDCI, Santorini Black
Post #949750 18th Apr 2022 3:16pm
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Mike c



Member Since: 11 Aug 2017
Location: Maldon, Essex
Posts: 930
England 2004 Defender 90 Td5 CSW Belize Green
Watching this thread as I have often considered a transfer box swap to 1.2 on my td5, however, most of my driving is on local roads or b roads so 30-60mph limit, only motorways a handful of times a year for holiday trips of which I am more than happy to stick to 60-65mph

In the in end I think that the standard box is more suitable Thumbs Up 2004 Defender 90 Td5 CSW
2002 Discovery 2 td5 GS (gone)
1994 Defender 90 300Tdi CSW (gone)
Post #949756 18th Apr 2022 3:36pm
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