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Andrew95



Member Since: 27 Jul 2022
Location: Midlands
Posts: 75
United Kingdom 1997 Defender 110 300 Tdi SW Corris Grey
R380 / LT230 Ratios
Now I have started doing a lot more overseas trips I am looking at improving the motorway handling of my 300tdi 110. Currently on 285/75's, fairly well tuned engine, with a moderate to heavy load. Not looking for increased top speed, just better manners - reduced revs, less stress on the engine, quieter etc.

I am looking at replacing the gearbox soon, so my original thought was when the T-box is out as part of this, replace the gearing to 1.3 (I don't want to go as high as 1.2) which from what I have read sounds ideal for what I am after and has really good reviews.

But, I only replaced the T-box a couple of years ago, its perfectly fine. So to save on cost and effort, do I keep the T-box as 1.4 and instead get the V8 5th gear in the R380.

There are pros and cons for both - I am wondering if anyone has any real world experience of either (ideally both!) and can comment?
Post #1077550 15th Oct 2025 9:36am
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el sid



Member Since: 06 Sep 2025
Location: devon
Posts: 21
England 1996 Defender 90 300 Tdi CSW Barolo Black
My 300tdi has a Romer overdrive,it reduces revs by 28%in all gears including low range,they cost quite a lot ,but mine came with one.im very pleased with it,just another option for you.
Post #1077554 15th Oct 2025 10:19am
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Andrew95



Member Since: 27 Jul 2022
Location: Midlands
Posts: 75
United Kingdom 1997 Defender 110 300 Tdi SW Corris Grey
That was my original though (has been for a few years), but they are so expensive and difficult to get hold of.
Post #1077557 15th Oct 2025 10:24am
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bankz5152



Member Since: 02 Feb 2017
Location: South London/North Kent
Posts: 2237
 2004 Defender 110 Td5 DCPU Epsom Green
Higher 5th is an excellent choice. Low rpms in 5th and better mpg.

I had 33s, 1.3 box and higher 5th on my old 110, new 110 has 33s and stock ratios. Everything else is pretty much the same.

Old 110 got almost 50miles more per tank!
Post #1077602 15th Oct 2025 4:42pm
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TexasRover



Member Since: 24 Nov 2022
Location: Paris
Posts: 1356
France 2002 Defender 110 Td5 DCPU Chawton White
The strain on the engine would actually be higher with lower rpm. You do need to watch for labouring the engine too much with high gearing hence an overdrive makes it easier to stay in the sweet spot.
Post #1077616 15th Oct 2025 7:16pm
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jst



Member Since: 14 Jan 2008
Location: Taunton
Posts: 8473
 2011 Defender 110 Puma 2.4 USW Stornoway Grey
This was the point I was going to make. Lower rpm might increase thermal load and engine stress, as alot of m57 conversions are finding out. Run the ashcroft calculator to get the correct rpm for rhe speeds you want. Cheers

James
110 2010 XS Utility
130 2011 M57 bespoke Camper
90 2010 Hardtop
90 M57 1988 Hardtop
Post #1077640 15th Oct 2025 9:52pm
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