1.667:1 transfer box in a disco?

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Russell 1

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Has anyone put a 1.667:1 or a 1.4:1 transfer box in a discovery? If so what does it drive like? I do a fair bit of towing and I find pulling away difficult with any sort of weight in the trailer. As it will need a new gearbox soon I'm thinking I could be wise to change the t box.
Motorways and driving over 50 are not needed where I live.
 
Don’t put the 1.6 on it will be useless.
1.4 will be fine but you will probally find your not using 1st gear (unless your trailer is fully loaded)
What size tyres you got?
 
What Disco in the first place? cos if i's D2 forget about that cos you mix up the whole management as the rpm will no match the expected VSS and the EGT can go up in the sky... i dunno about D1 but if it's automatic with EDC it might have issues too
 
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I have a 1.6 in my RRC thats fitted with a 300tdi/auto from a Disco 1 and 285 tyres. Fitted it as it struggled....due to traffic....to get fast enough for top gear lock up. So yes it revs more than before but its better than running around changing back and fourth between 3rd 4th, now it locks up about 40mph and pulls fine

If I had a 1.4 id have fitted it.
 
sierrafery said:
What Disco in the first place? cos if i's D2 forget about that cos you mix up the whole management as the rpm will no match the expected VSS and the EGT can go up in the sky... i dunno about D1 but if it's automatic with EDC it might have issues too
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Im not up on the abbreviations but yes it is a disco 2, td5 manual. Do you really think it will upset the computer?
I was thinking 1.6 because I will probably fit bigger tyres at some point.
 
Russell 1 said:
Im not up on the abbreviations but yes it is a disco 2, td5 manual. Do you really think it will upset the computer?
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I'm convinced about that... better get a proper remap rather than play with transmission ratios, if your tyres are bigger than standard that's the first reason of it's lack of power
 
EeEk said:
I have a 1.6 in my RRC thats fitted with a 300tdi/auto from a Disco 1 and 285 tyres. Fitted it as it struggled....due to traffic....to get fast enough for top gear lock up. So yes it revs more than before but its better than running around changing back and fourth between 3rd 4th, now it locks up about 40mph and pulls fine

If I had a 1.4 id have fitted it.
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What size are your tyres in inches? 35?
 
Current tyres are standard but would like a 33" set. I don't want tune it as it's done 190,000 miles.
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Bigger tyres would cause much more harm than a remap for a Td5.... a good remap has no ill effects for the engine no matter of mileage, on the contrary, while bigger tyres = higher EGT which kills the engine slowly...that's a fact... to not speak about how gutless it will be with bigger tyres and no remap
 
EeEk said:
Bigger tyres - lower gearing = same :)
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Not for electronic management which has a fuel map with all the elements in it ''calibrated'' for factory fitted tyres, the VSS(vehicle speed signal) included and this is altered by bigger tyres(hence the speedo reading) and will not mach in the map with the others at the same physical speed , rpm, throttle input, etc... it's very complicated, i explained it few times in this forum
 
I'm trying to get my head around how the egt would rise due to different gearing. I had a quick read and it looks like more fuel means higher egt and incorrect timing, leaky valves and restrictive exhaust will do the same. I'm not arguing but I can't see why the egt would rise.
Edit:

Unless I suppose it is counting on the cooling effect of the intercooler, are these things tuned that close to their limit ,134hp from a 2.5l?
 
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It's too complicated... different gearing or tyre dimension means different throttle demand and rpm(engine speed) to achieve the same VSS(vehicle speed) and torque ... that's the gist of it cos those elemens will not match as they were mapped from factory and the ECU will start compensating with fuel to get to the proper algorythm so the EGT will rise... i made various live tests beside hard study of how the fuelling works and i've seen how the EGT behaves with my own eyes, believe me or not but if you dont and you fit big tyres at least fit an EGT gauge too if you want to be on the safe side
 
I'll try to put it in the most simplistic way but in reality is much more complicated:

on a Td5 as it let the factory when you push the throttle in a certain gear there must be a certain rpm, torque and vehicle speed(amongst others like air flow, boost, engine temp, etc,), each element has it's own effect and it has to match with mapped values as the IQ(injected quantity) calculated by the ECU to be optimal hence the EGT within decent limits... once only one of those elements is out of the mapped range the IQ is affected.... the first sign is that the more weight you put on the vehicle or you tow the higher the EGT and lower the power will be.... i can't put it simpler than that while this is just an extremely rough explanation
 
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Maybe for defender which has a different management even with same ECU and engine but that kit has nothing to do with D2 which has electronic VSS delivered by the SLABS ECU and even if it is corrected that doesnt correct the different torque and rpm at a certain driver demand(TPS input) ... for the D2's management the only correct way is a proper remap
 
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