90 Mellis Posted August 21, 2007 Share Posted August 21, 2007 After some advice-I'm in the process of doing a 200 Tdi conversion on my 1986 90. I have the option of using the standard 90 transfer box or one from the donor Disco 1!? I believe the Disco trans box is higher ratio. I want the vehicle to be a good all rounder i.e Good road speed but still low enough geared for the off roading!? Any ideas as to which would be most suitable?? Quote Link to comment Share on other sites More sharing options...
LandyManLuke Posted August 21, 2007 Share Posted August 21, 2007 Low range is the same in both, so no problems off road there. the lower ratio (higher gearing) disco box will give you more relaxed road speeds, shouldn't have any problems unless you're running massive tyres or regularly pull heavy trailers etc. Quote Link to comment Share on other sites More sharing options...
Mark Posted August 21, 2007 Share Posted August 21, 2007 What size tyres are you running? I am going to put a defender (1.4) transfer box on my disco when I go up to 235/85 16 tyres (~same diameter as 750-16s) so if I were you I would stick with the 1.4 t-box Mark Quote Link to comment Share on other sites More sharing options...
Ex Member Posted August 22, 2007 Share Posted August 22, 2007 I agree with LandyManLuke. I have a 200TDI 90. Unless you are running tyres 35" or larger or pulling large trailers, the Disco t. case is better. Quote Link to comment Share on other sites More sharing options...
LandyManLuke Posted August 22, 2007 Share Posted August 22, 2007 It's worth adding, it does depend on your driving style & preferences, it might be a good idea to try and find one to drive before you commit. Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted August 22, 2007 Share Posted August 22, 2007 I've heard tell you can use a thing called "maths" to work out the gear ratios for your setup and thereby decide which would suit you best... ISTR there's even a handy excel spreadsheet in the tech archive that does these "maths" for you. Quote Link to comment Share on other sites More sharing options...
mmgemini Posted August 22, 2007 Share Posted August 22, 2007 I believe the Disco trans box is higher ratio.I want the vehicle to be a good all rounder i.e Good road speed but still low enough geared for the off roading!? Any ideas as to which would be most suitable?? If you want it higher geared then you need to fit a LOWER ratio like the Discovery box. Don't worry even the technical wrighters don't know the difference between a high ratio and high gearing mike Quote Link to comment Share on other sites More sharing options...
nickm Posted August 22, 2007 Share Posted August 22, 2007 If you want it higher geared then you need to fit a LOWER ratio like the Discovery box. Don't worry even the technical wrighters don't know the difference between a high ratio and high gearing mike I have a disco 200tdi lightweight hybrid running the disco T box (standard fuel pump setup) find I need to slip the cluth alot with fedima 36's just pulling away from lights etc, would think a 90 T box would be better for daily use, should be fitting a 110 T box soon so hopefully that'll improve use around town Quote Link to comment Share on other sites More sharing options...
Litch Posted August 22, 2007 Share Posted August 22, 2007 Unmodified 300TDi 90 on 265/75x16's fitted with Disco transfer-box. Fantastic conversion and I can't recomend it highly enough. I always advise people to try before fitting and am willing for anyone to have a drive in mine if they are local but in my opinion, when commuting, motorways, headwinds, hills, towing & off-road etc it is much better than the standard gearing. Quote Link to comment Share on other sites More sharing options...
Shox Dr Posted August 23, 2007 Share Posted August 23, 2007 Unmodified 300TDi 90 on 265/75x16's fitted with Disco transfer-box. Fantastic conversion and I can't recomend it highly enough.I always advise people to try before fitting and am willing for anyone to have a drive in mine if they are local but in my opinion, when commuting, motorways, headwinds, hills, towing & off-road etc it is much better than the standard gearing. It matters not from where the transfer box came from. Disco's can have the same ratio other models If you are lucky a sticker next to the PTO outup plate will asdivse of the box ratio List of Serial numbers and corresponding Ratios All stock LT 230"s have a low ratio of 3.321, the following list refers to the high range ratio. 12D = 1.667 LT 230R 13D = 1.410 LT 230R 14D = 1.003 LT 230R 15D = 1.192 LT 230R 20D = 1.667 (2.5 N/A 110), 22D = 1.410 (all 4Cyl 90/110 bar above), 25D = 1.410 (V8 110 LT 85), 26D = 1.003 (RR Classic 3 speed auto), 27D = 1.192 (early RR Classic), 28D = 1.222 (RR and Disco I), 29D = 1.192 (V8 90 LT 85), 32D = 1.222 34D = 1.410 (2.0 Disco I), 36D = 1.211 38D = 1.211 40D = 1.211 (NAS/Japan 90&Disco), 41D = 1.211 (Disco II, diff lock stud), 42D = 1.211 (Disco II, diff lock stud), 43D = 1.410 (90/110 TD5), 57D = 1.410 (90/110 TD5), 61D = 1.211, 62D = 1.211, 68D = 1.211, 69D = 1.211, 70D = 1.211 (Disco II, no diff lock), LT 230 Transfer case comparisons 1.003 > 1.222 = 17.92% Drop 1.003 > 1.410 = 28.86% Drop 1.003 > 1.667 = 39.83% Drop 1.222 > 1.003 = 21.80% Raise 1.222 > 1.410 = 13.33% Drop 1.222 > 1.667 = 26.70% Drop 1.410 > 1.003 = 40.57% Raise 1.410 > 1.222 = 15.38% Raise 1.410 > 1.667 = 15.41% Drop 1.667 > 1.003 = 66.20% Raise 1.667 > 1.222 = 36.41% Raise 1.667 > 1.410 = 18.22% Raise For those considering a ratio change the following may prove useful. MPH per 1000 rpm = 2.976D/ MTR Quote Link to comment Share on other sites More sharing options...
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