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1.4:1 or 1.2:1 200TDi


ajh

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I am wondering if anyone who has fitted a 1.2:1 transfer case to a tuned 200TDi (say 130-140bhp) regret making the swap when used mostly for highway / long-distance driving (so 32" tyres).

I know my front diff needs replacement and my rear needs rebuilding, and my TC is likely ready for rebuild as well (some movement but it has 260,000mi on it so just replacing everything with Ashcroft units seems sensible now.

I am currently at over 3000rpm at 125kph and I am thinking I am running way too far from peak power. That and it's pretty loud.

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Really? Nobody? Doing this is not cheap and having some feedback would be nice. There just are not enough people with tdi around here to get any kind of real-world opinions locally.

I suppose going 1.2 and then if it ends up too high it could be "adjusted" at the diff.

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Ashcrofts do a conversion for 300 or td5 defenders i think it gives a 15% increase in gearing ,

I havenot done the conversion you are contemplating , but have experience with lots of modifications on many different land rovers , so just trying to give you a few things to consider. Vehicle usage is a big one JMHO

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Even at 150-160bhp? The problem right now is by the time I get to 125 the torque curve has collapsed. Are you guessing or have you tried?

I've heard a few people say TDi 110's are overgeared at 1.222, it's been talked about many times on here. I'd also ask if you're guessing with the 130/140/150/160/3x10^7bhp TDi and its collapsing torque curve. Using the dyno sheet and the gear ratio calculator in the tech archive you should be able to match your gear ratios pretty well.

When you say it's not cheap, a decent 1.222 LT230 should cost all of £50 as there's only about a million of them out there in rusty RR's and Discos, so you can try it and then go for a rebuild if you really feel the need.

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I run my V8 Ninety auto on 33s and have found it struggled with a 1.22 TC if there was a hill or trailer involved. Now with a 1.4 it's much better to drive.

So factor in a 110, and 200Tdi, I think I would stick with your 1.4. It depends upon your intended use of course, style of driving, heavy loading etc.

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If you can find a decent lt230 in Canada for 50 quid I will take 10.

I will be dyno testing, hopefully I can do it next week (this week I am stuck running a major international conference so not a lot of time to do more than discuss things. )

I will do the ratio calc based on a variety of ratio and r&p combinations and see how it works out. If I got 10% taller gearing in 1-4 it would probably be ideal, if 5th was 30% higher which leads me to think that perhaps 1.2 and 3.75r&p might work.

I was just hoping to chat with people who have sorted things. Right now power is great off the line but 1st is shorter than ideal but starting in 2nd is too tall by roughly the same amount. Then at about 90kph things slow dramatically and changing to 5th doesn't really help that much as power is still best about 1000rpm lower.

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changing to 3.75 crown wheel and pinion? these were just about strong enough for a series landrover, I have tried kam strengthened 3.7 cr and p and broke them plus getting spares was slow.

a mate of mine runs his izusu powered 90 with 1.2 transfer and 33"tyres and he loves it but he has a 110 for towing.

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I have a 300 tdi 110 with disco box on std size tyres. With a std engine it would have been putrid; but it has a full width intercooler, some gasflowing mods and a tweaked pump. Sometimes it tows a horsetrailer. The only problem is setting off on hills, but I use low for that. Solo performance generally is miles better, the gears give you that bit more, and 4th is very useful when towing. I'd not go for the disco box unless the engine has been tweaked.

Nigel

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I've got a 1.2 behind a tweaked 300Tdi and autobox on 33s - not quite the same drivetrain, and I'd say it's "steady" with the 1.2 box, 2200rpm is 70mph and it's lacking the power to accelerate at that roadspeed/engine speed combination.

I changed from a 1.6 ratio box, where 80mph was about all it'd give, and the noise was unbearable. With hindsight, I'd have gone for a 1.4 but it's there now so I'll uprate the intercooler, play with the turbo a bit more (and fix the crack in the exhaust manifold...) and see if I can push it along at 1.2 so I can enjoy the better fuel consumption. If not, as Fridge says, we have the benefit of cheaper t-boxes over here.

You could get a pair of crownwheels and pinions shipped over for a similar price to the t-box, it seems, and then you've got a wider choice of ratios to target your gearing at. You could try some comically large tyres to "feel" what the ratio calculator results are like to drive? My lesson: remember that 500rpm is "a lot"!

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Thanks for all the opinions, I've decided to go for the 1.2 in a q-suffix from Ashcroft as my real worry is highway driving and expedition where there is always low-range and I am unlikely to tow often and then the heaviest thing is likely to be another 110.

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changing to 4.75 crown wheel and pinion? these were just about strong enough for a series landrover, I have tried kam strengthened 4.7 cr and p and broke them plus getting spares was slow.

a mate of mine runs his izusu powered 90 with 1.2 transfer and 33"tyres and he loves it but he has a 110 for towing.

3.75/4.75 oops

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Autos arent a good comparison, because the gearing is totally different to a manual.

Peak power on a TDI is around 4000rpm, yes the torque is dropping, but that doesnt really matter.

I'd imagine on a tuned engine, a 1.2 will be fine. On a standard truck, especially 110's with their extra weight, it may struggle a bit.

It will also depend on your criteria of whats acceptable performance. For me, 110hp in a landrover would be abysmal, regardless of the gearing, yet plenty people think they're perfectly fine.

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  • 2 weeks later...

Thanks to Ashcroft getting me the case quite quickly it is now in place (though I get the new front diff on Wednesday and still need to stretch the front shaft and balance both) vibration is significantly reduced and the shift points are where I'd expect now with about 110kph in 4th and 120kph in 5th. Loads less noise and it doesn't feel like the drivetrain is on the edge of blowing up on the highway anymore.

Overall I am very happy with the change. I can now continue to tune things and get the top and up a bit as well. Maintaining 125kph on a 8% grade would make me really happy.

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