200tdi running 1.6 transbox swap to 1.2?

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300bhp/ton said:
I think I can answer most of the questions.

Most likely is a 1.6:1 transfer box. But if you didn’t get it straight from the Military then it might have already been swapped for a 1.4:1

Do you know what sort of top speed you can get currently?

As for changing the gearing. The transfer box is the easiest and cheapest option for the most part. Although you could change the diffs as an alternative. You could also fit an Overdrive unit like Roamadrive. But they are pricey. But would essentially give you an extra cruising gear.

What tyre size are you running? And do you plan to run bigger at any point? The bigger the tyre the taller you overall gearing will be. So short gears can be good.

Also do you off road?

I know you said no towing. Not sure on your age. But if under 40, then the law has changed so everyone can tow 3.5t. A 110 would be good for this. So I guess you might want to consider it for the future.

BTW - for motorway use. Taller gearing will allow lower rpm at cruising speed. And to some extent higher cruising speeds. But there is a point this becomes untrue as you’d need to drop a gear to maintain the speed due to lack of power & torque.

This means you will get less rpm noise. But if I’m honest, most of the noise in a Land Rover. And esp an ex MOD one is not the engine rpm. Just don’t expect it to completely transform the noise levels.

Is your engine tuned?

Personally I’d suggest a stock power Tdi running normal 235/85 or 7.50 tyres would be under powered with a 1.2 transfer box. A tuned one will pull the gearing fine. But will feel less perky than your current setup.

My recommendations would be a 1.4:1 transfer box.

Or retain the 1.6:1 and fit an Overdrive. You can use the gearing calculators to see how they would compare at say 65mph in terms of revs.
Click to expand...
Wow loads of information thanks you. So I'm 31. But I can't see I'd ever need to tow. Not bothered for horses or livestock. Or caravans to be fair. I haven't got it myself directly from the mod so I guess the box could be different but as it's got a disco 200tdi I'd think they'd pulled the 1.2 rather than sorcing a 1.4? I get if I'm feeling adventurous and frivolous 75mph top speed give or take. I generally drive at 60mph. I'd like to off road it occasionally but as its my daily and my work van I don't want to ruin it as the chassis is in shockingly good nick, but I'd love to off road it. Don't know if it helps but I generally get 30MPG. I have recently been working on the motor the back has 5 layers of insulation for heat and noise. Aswell as 4 layers on the doors at the front. I'm yet to attempt sound proofing the floor/bulkhead/roof does the seatbox help? I dont expect the thing to be a car I don't expect it to be a cruiser. But anything past 50mph on the motorway is just scary sounds like I'm killing the bloody engine. I'd say I can easily drive in 5th gear at 25/30mph at this point it almost becomes an automatic. Just a question does the gearbox being full of oil dampen a lot of sound as I know the lt77 let's oil out and I've not been under to see if it has much left in it to be fair. Im not sure of my tyres don't feel there overly large. Not with the truck to check atm.
 
Mac-1990 said:
Thanks mate this is exactly the kind of answer I was hoping for. Have you driven a 1.4 with a tdi?
Click to expand...
I will have driven a standard 300tdi at some point, but not recently, so can't remember specifics. Defenders on standard ratios always seem to feel a bit revvy to me, but this tends to keep the turbo on boost. Where mine feels a bit sluggish on long hills, it is because the revs are too low and the turbo isn't doing its bit. If you can hear the turbo working it pulls like a train.
If you still have the military LT77, the first gear is lower than the standard box, presumably to cope with the 68bhp of raw power from the 2.5N/A.
You don't say what tyres you are running, that would be a big cnsideration.
 
Rougharse Racing said:
I will have driven a standard 300tdi at some point, but not recently, so can't remember specifics. Defenders on standard ratios always seem to feel a bit revvy to me, but this tends to keep the turbo on boost. Where mine feels a bit sluggish on long hills, it is because the revs are too low and the turbo isn't doing its bit. If you can hear the turbo working it pulls like a train.
If you still have the military LT77, the first gear is lower than the standard box, presumably to cope with the 68bhp of raw power from the 2.5N/A.
You don't say what tyres you are running, that would be a big cnsideration.
Click to expand...

I've read that before about the military lt77 having a lower 1st. Its a green box so I guess it is military. 1st gear wouldn't make any difference to the whole drive after first though would it. I mentioned this to my fred in the shed mechanic who claims to be a landy boff. He told me there is only one lt77. I secretly thought to myself he was mistaken. Yeah not sure what tyres are on it, not with the truck atm To check. I think they are standard size. Defo not oversized chunky monkeys.
 
Mac-1990 said:
Thanks mate this is exactly the kind of answer I was hoping for. Have you driven a 1.4 with a tdi?
Click to expand...

i have a 200tdi in a mil 90 with a military lt77 with a 13d lt230 1.4 and it’s good, plenty of acceleration and it will cruise at about 70 and I have no issues towing

Search for the 0-60 thread as there are some videos on there of acceleration times with various boxes.

edit: I can’t find the thread but here is the video of my 90
 
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Mac-1990 said:
I've read that before about the military lt77 having a lower 1st. Its a green box so I guess it is military. 1st gear wouldn't make any difference to the whole drive after first though would it. I mentioned this to my fred in the shed mechanic who claims to be a landy boff. He told me there is only one lt77. I secretly thought to myself he was mistaken. Yeah not sure what tyres are on it, not with the truck atm To check. I think they are standard size. Defo not oversized chunky monkeys.
Click to expand...
Tdi's use different gear-sets to earlier LT-77's. Pretty sure Ashcrofts gearing calculator shows all of them, including the ratios.
 
I have a 200Tdi 90, swapped out the std T'box for a disco one some years ago, I run Cooper discoverer stt pro in 235/85/16 and from new these are tall for their size if that makes sense. Definetly sluggish to pull away, so I made a few gentle tweaks to the injection pump, which pretty well got it back to how it was before, but, with a trailer there is a noticeable difference, about half a gears worth, but I don't tow much these days so thats all right.
The major difference is that below 40 I really need to be in 4th and usually shift up into 5th around 45, but she still pulls well. I have no problem driving at 70 (or over) but usually stick at that in consideration of her age, when I feel like it I can easily get 50 in 3rd. Where I live in France there is little traffic on the roads and most places I want to be are 1/2 hour plus away, so the more relaxed drive is good for me. I do drive off road a fair bit but as has been said, low range is unchanged.
Altogether I am very happy with the set up.
 
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