R380 / LT230 gearing advice

Hello all,
Advice please!
I am about to pull the trigger on a rebuilt T-box for a 110 Defender (1998 300TDI)

I dont tow, I do drive a lot on the highway / motorway.

I want a quieter, nicer motorway drive.

I'm attempting to emulate my Discovery 300TDI Auto box ride.

Do I opt for a 1:2 T-box? and will this behave in a similar manner to the described Disco drive? Are there any other considerations in respect of the R380 manual gearbox with a 1:2 T- box??

Ive had a look online for answers and have got nowhere... I want to understand the 'real world' driver experiece of the above before I dump a shed full of hard earnt loot on this project!

Thanks in advance
Sean.

the only difference between the disco and defender would be the tyre size

@jamesmartin thanks for the reply. So no issues with the 1:2 T-box in respect of the R380 compared to the Disco 300TDI auto box??

Gibraltar Sean said:

@jamesmartin thanks for the reply. So no issues with the 1:2 T-box in respect of the R380 compared to the Disco 300TDI auto box??

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no r380 and the lt230 are same as fitted in manual disco so are the diffs so its only tyre size that might vary,defenders tend to run taller tyres so it ups the gearing as such

Yep, many thanks, I have posted and had a lot of similar feed back from Facebook groups too. Thank you.

jamesmartin said:

the only difference between the disco and defender would be the tyre size

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That and the entire NVH package is completely different on the Disco. Most of the quieter ride they offer is not really the gearing. But being constructed in a very difficult way to a 90/110.

300bhp/ton said:

That and the entire NVH package is completely different on the Disco. Most of the quieter ride they offer is not really the gearing. But being constructed in a very difficult way to a 90/110.

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1.2 lt230 fitted to 300 tdi disco is the same as fitted to defender r380s are the same except the gear change,diff are the same only variant is tyre size,later q boxes are equivalent on both they just have finer teeth than tdi boxes

Gibraltar Sean said:

Hello all,
Advice please!
I am about to pull the trigger on a rebuilt T-box for a 110 Defender (1998 300TDI)

I dont tow, I do drive a lot on the highway / motorway.

I want a quieter, nicer motorway drive.

I'm attempting to emulate my Discovery 300TDI Auto box ride.

Do I opt for a 1:2 T-box? and will this behave in a similar manner to the described Disco drive? Are there any other considerations in respect of the R380 manual gearbox with a 1:2 T- box??

Ive had a look online for answers and have got nowhere... I want to understand the 'real world' driver experiece of the above before I dump a shed full of hard earnt loot on this project!

Thanks in advance
Sean.

Click to expand...

A 1.2 transfer box should reduce cruising rpm and allow higher speeds in each gear compared to the same setup with a 1.4 transfer box.

However it is worth noting, as mentioned above. A stock Discovery runs smaller tyres (~29" tall) vs most 90/110's (~32" tall). This means the mph/1000rpm for a Discovery works out to about the same as a standard 90/110.

If you are running 32" tyres on the 110, then adding a 1.2 t box will over gear it compared to stock. The result is, it will generally blunt acceleration a bit. And you may find you lack power to pull 5th in some scenarios with a stock Tdi engine. Meaning you might have to drop to 4th more often.

Cruising rpm at 70mph is only going to be about 400rpm lower with the 1.2 vs the 1.4, this really isn't going to transform the vehicle in terms of noise. I'm willing to bet the db level will barely change. Although it might 'feel' like you aren't driving as hard. Lower speeds in top gear the rpm difference will be less, e.g. 50mph only 300rpm difference.

jamesmartin said:

1.2 lt230 fitted to 300 tdi disco is the same as fitted to defender r380s are the same except the gear change,diff are the same only variant is tyre size,later q boxes are equivalent on both they just have finer teeth than tdi boxes

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Yes, but the better cruising of a disco comes from having a 1 piece body tub, mounted on rubber donuts and other NVH items. Compared to a Defender with a multi piece body bolted metal to metal on the chassis. It makes for much more refinement in a Disco/RRC.

300bhp/ton said:

Yes, but the better cruising of a disco comes from having a 1 piece body tub, mounted on rubber donuts and other NVH items. Compared to a Defender with a multi piece body bolted metal to metal on the chassis. It makes for much more refinement in a Disco/RRC.

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yes but that has nothing to do with altering t/box ratio, with the 1.2 box fitted in a defender you have the same ratios as disco but usually taller tyres,its the tyre were over gearing is going to occur

jamesmartin said:

yes but that has nothing to do with altering t/box ratio, with the 1.2 box fitted in a defender you have the same ratios as disco but usually taller tyres,its the tyre were over gearing is going to occur

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Exactly

That's what I'm trying to say to the op. Changing the tbox won't make his 110 cruise like a Disco. It isn't really about the gearing, but the vehicle.

Thanks chaps! Im understanding more here! So I get the body is different between a Defender / Disco, but surely the 1:2 T-box gearing should make the engine quieter and thus not sound like its thrashing its self, compared to the 1:4 box....?

Gibraltar Sean said:

Thanks chaps! Im understanding more here! So I get the body is different between a Defender / Disco, but surely the 1:2 T-box gearing should make the engine quieter and thus not sound like its thrashing its self, compared to the 1:4 box....?

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Yes, engine noise will reduce, but as mentioned in post #8, not by that much.... you could do a test after some simple arithmetic... work out the speed difference with a change in engine revs of 400 rpm, then drive at the two speeds - the noise at the higher speed should be roughly reduced to the noise at the lower speed ...

IMO, getting the rid of the R380 - replacing it a ZF4HP24 would be a better option in improving the driving experience of your deafener .... it won't improve your bank balance though!

Then you could get a FWIC and tune the 300Tdi too......

I have a 1.2:1 transfer box in my 300tdi 110 with military (lower first gear) LT77 gearbox and 750x16 tyres. the tyres are quite tall for 750's.)
On occasion, whilst towing a horse box, it feels a bit over gerared on hill starts, but is otherwise ok.
I fitted the 1.2:1 box as it previously had a 1.6:1 box and the 1.2:1 box came with the 300tdi engine.
If you have tall tyres it is probably not worth changing from a 1.4:1 box, unless your existing box is knackered.
It still drives like a Series 2 body bolted on a Range Rover chassis, with sightly less engine noise than before.

If you are getting a t-box rebuild you could go for a intermediate ratio 1.3:1?
Or you could consider an overdrive fitment?

Thanks for the advice all.
I believe there is no perfect soloution here, but...
I leaning towwards both a 1:2 ratio and 16/85/235 tyres
Reasons:
1. I'm in a position to change out the T-box, so that's that... I need to choose the most appropriate.
2. I'm not happy with the racket, high revving of the 1:4 - I'm clear on that so there needs to be change! Basics: (in my mind...) above .4 adds to the issue / below .4 lessons the issue so that has to be the direction.
3. Cost: to put in a .3 will cost more loot and is very close to the .4, so... I'm edging away from this option.
4. .2 is as per the auto box disco I had in the past, so I know it worked there...yes there are considerations with the tyre size, but on that disco I ran with 16/75/265 - all good, happy!
5. I am not adverse to converting to an auto box IF the right conditions present at some time in the future - someone with the knowledge & ability to fit it and cost considerations etc...

So, I think that is it. This might not be a total night and day effect that I may desire, BUT, my assessment is that it hopefully moves me from a point (currently) further away from where I want to be, to a point (nearer) to that where I wish to be... I really appreciate all the feedback and the time taken by the commentors on this thread. This info with other online FB groups, (I have posted the same question) has settled my mind as to the direction I need to take.
Thank you all!

Sound proofing helps a lot. Dodo mat Deadn Duo on the inside of the cab, doors, seatbox and tub + Dodo 7mm thermo liner in the engine compartment (bulkhead) and underneath the cab and seatbox and up under the rear tub.
The 7mm liner can also go on the roof. https://www.deadening.co.uk/collections/dodo-mat

miktdish said:

Sound proofing helps a lot. Dodo mat Deadn Duo on the inside of the cab, doors, seatbox and tub + Dodo 7mm thermo liner in the engine compartment (bulkhead) and underneath the cab and seatbox and up under the rear tub.
The 7mm liner can also go on the roof. https://www.deadening.co.uk/collections/dodo-mat

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Thanks Miktdish... I have contacted Wrights Offroad to add this element to the mix... again as with the power steering box (which has forced this whole event...) If I add to the T-Box pallet, I will save on shipping costs.
I have used the Wrights Offroad in the Military Wolf and found it to be awsome at 'noise kill' also, I know it is durable and you simply hose out the 'clag' when cleaning with no deteriation to the acoustic matting.
That said... always open to other suggestions, maybe I will open a specific thread...
Thanks, Sean.

I have that same system in my Defender, with dodo 'deadn mat' underneath ...

I've got a disco transfer box in my 200tdi 110, 235/85r16 tyres plus lots of sound proofing. Go for it..
Much more relaxed crusing, much quieter, and better mpg I get 32 overall..
I do occasionally tow, a 3/4 ton boat on trailer..no problem.. just change down a bit more often...