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It should have a 1.6 already, but who knows what has been done to it since it was demobbed?  Even the serial number on the casing is not reliable, as it may have been rebuilt with a different ratio.  The only way to know would be to open the rear and bottom covers and count teeth.

If you’re changing the 12J engine for something with a bit more poke, and I think you said you’d be sticking with normal sized tyres (7.50 or 235/85), then I think 1.6 is going to be a bit of a nuisance, even in town.  It’d not only give a low top speed, but would also put the gears closer together on the speed range, so you’d be changing gears a bit more often.  I think you need to decide on which engine you want first and then select a transfer box to suit, but a 1.4 is probably going to be the best bet - that’s why they’re standard on most 90s, 110s and Defenders.

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3 hours ago, Snagger said:

would also put the gears closer together on the speed range, so you’d be changing gears a bit more often

If you've got a V8 just leave it in 3rd, you can go from pulling away to motorway speed without stirring the stick :P

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I'm gonna come in from an different angle here, and make a case for longer gearing. If you want more revs, you can always keep it in a lower gear for longer, but you can never add a 6th (unless you fit an overdrive). My 4.6 P38 with the R380 is usually in 5th from 30mph on, and will smoothly pull if needed. For cruising I want the revs as low as possible (some might say too low). Same reason in the Esprit I fitted a longer 5th from a later V8, to allow more relaxed high speed cruising.

If I want more grunt for overtaking (in either car), I simply take it back to 2nd or 3rd and get all the revs and power I need. I am going to the trouble of fitting a lower 1st gear to the R380 (dieselgears in a V8 box, not as easy as I thought...) for the project Range, to spare the clutch when setting off with a heavy trailer and to have more control off road. And because it seemed fun/special to do... Also taking into account the 33s I plan to fit. Both Rangies will have a standard Borg Warner transfer case, 1.2 ratio. Short(ish) first and long 5th and some in between to fill the gap should suit the V8 just fine.

In your case @Junglie I'd start with a cheap 1.2 box and see how that goes. You can easily change later on, should you feel the car is over geared.

Filip

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5 minutes ago, Escape said:

I'm gonna come in from an different angle here, and make a case for longer gearing. If you want more revs, you can always keep it in a lower gear for longer, but you can never add a 6th (unless you fit an overdrive). My 4.6 P38 with the R380 is usually in 5th from 30mph on, and will smoothly pull if needed. For cruising I want the revs as low as possible (some might say too low). Same reason in the Esprit I fitted a longer 5th from a later V8, to allow more relaxed high speed cruising.

If I want more grunt for overtaking (in either car), I simply take it back to 2nd or 3rd and get all the revs and power I need. I am going to the trouble of fitting a lower 1st gear to the R380 (dieselgears in a V8 box, not as easy as I thought...) for the project Range, to spare the clutch when setting off with a heavy trailer and to have more control off road. And because it seemed fun/special to do... Also taking into account the 33s I plan to fit. Both Rangies will have a standard Borg Warner transfer case, 1.2 ratio. Short(ish) first and long 5th and some in between to fill the gap should suit the V8 just fine.

In your case @Junglie I'd start with a cheap 1.2 box and see how that goes. You can easily change later on, should you feel the car is over geared.

Filip

It's not just about revs IMO. It is about character. Simply using a lower gear doesn't achieve this, because with tall final drive gearing the speed range is large within each gear, which can make an engine feel less peppy and exciting, as you'll relatively slowly wind it out to the red line.

Shorter gearing will allow the engine to rev much more quickly, making it feel far more exciting, even if it isn't hugely quicker (although it can make quite a difference to performance). A tall 5th gear I agree can be handy for cruising. But you can often achieve this just by using a different 5th gear ratio (or an Over Drive unit with the 1.4 transfer box).

Ultimately it comes down to what the owner intends to use the vehicle for and their driving style. If all you want to do is cruise and almost never wind it out to the red line. Then tall gearing works well for this. If you want to grab it by the scruff of the neck and give it a good pasting, banging through the gears. Shorter gearing will likely be far more exciting, heart pounding and grin inducing :D

Using my TR7 as an example. I used to run a 3.08:1 rear axle, which gives it pretty tall gearing. Tall enough that I clocked it at over 140mph. However due to money constraints at the time, when I broke the rear axle I replaced it with one running 3.9:1 CW&P. Now I fully admit it is bloody useless on the motorway and will only cruise at 60-65mph and still feels like it is high in the revs. Top speed is also only 112mph at the red line in 5th. But the change in character was dramatic. It almost felt like you'd gained 100hp more. In this guise it is a far more entering car than ever it was before. So much so that is has now been running this gearing for the past 10 years. I do have a 3.45:1 gear set, which I think will be a middle ground between fun and better practicality. Although the reality is, this car just isn't built or owned for practicality. Although it would be nice to maybe drive the NC500 or tour Europe in it at some point. Which really would mean changing the gearing. But for bombing around B roads in a semi rally car style. The current gearing is ideal.

 

For a 90/110 the use case may well be different. The 90 we have just put the 3.9 EFI in, it goes well. It never feels like it is lacking power. 5th gear 30mph pulls to 50mph no sweat at all. No need to down shift. But even if you drop it to 2nd gear at 30mph and blast it, somehow it still feels a bit lazy as you'll be in 2nd gear for a long time then get a single gear shift to 3rd before you are at illegal speeds.

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I can certainly understand your point of view, by dropping the final drive and/or transfer ratio the gearing becomes more close ratio. Not what most would want in a 90/110 I'd think, but that comes down to personal preference.

Your TR7 sounds like a blast! I followed one in New Forest a couple of years ago. Not sure if it was a TR7 or TR8 but it definitely had a healthy V8 and a driving style to suit.  😎

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Running the engine at very lazy revs with tall gears is softer on the ears, but it’s tough on the engine - you’re getting a lot of force on the crank shaft journals without much oil pressure.  It also means the water pump isn’t turning fast for the engine load.  They’re problems that standard or lower gearing won’t give you.

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I can't remember the name of the member, but there was someone on here with a Disco 1 200 shape running a V8 that had issues with the tuning when it was running 1.2, 33" tyres. swapping in a 1.4 made it more economical too if I remember correctly. Anyone else remember the thread I'm thinking of?

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I've opened a real can of worms here, haven't I?

I need to check for sure what I currently have fitted, and then go on from there. I suspect if I have a 1.4 I'll keep it. If it's a 1.6 then I might, or I might swap  it out for a 1.2.

Probably I'll keep it whatever it is initially as the Frankentruck is starting to eat a bit more money than I had planned.

Yes, I know that at least 90% of you are now smiling and remembering the days when you too thought that Landy ownership would just be a cheap laugh...

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If I were you. I’d run it as is too. But it would be good to figure out what you have. 
 

I do think for myself I’d like the 1.6:1 best. And would allow you to run 255/85R16 or 33” tyres without blunting performance. But I will admit it might be a bit revvy for some. Interesting the S. African 2.8 BMW petrol 6 pot Defenders (factory built) used the 1.6 transfer box. The 2.8 makes a bit less torque and revs a little higher. But similar power to a good 3.9 V8. 
 

However I suspect the 1.4:1 is probably the sweet spot to cover all bases. And if you wanted better cruising you could either go Over Drive or maybe just a different 5th gear ratio. 
 

Despite the fact I have a 1.2:1 on my 200Tdi. It isn’t the transfer box I’d pick unless running 29” or smaller tyres. 

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It’s prudent to work out what you have and run it as is for a while to work out what you need.  Diving straight in and replacing stuff before settling in with the vehicle will lead to some wrong decisions and money wasted.

With anything other than a 2.25 petrol or the normally aspirated diesels, 1.6 will be too low on normal tyres, unless you only drive in town or almost all off road.  But try it first and see if it’s a bit too low or much too low before trying another ratio.  The beauty of changing transfer ratios is that they’ll be robust and don’t introduce more maintenance or failure points and they’re cheap - the 1.22 and 1.4 ratio units are very common and cheap, so they should cost less than the sale of a 1.6 or other rare ratio unit.  An overdrive on a 1.4 is far more flexible, but is also far costlier than a 1.22 or the extra fuel used with a plain 1.4; if you look at Ralph’s (Western) troubles with his GKN, a fairly typical experience, and the prices of Roamerdrive (you’d be very lucky to find a second hand unit), then the overdrive seems less attractive.  So yes, you need to know your starting point and your intended destination before plotting a path!

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