naci Posted January 21, 2009 Share Posted January 21, 2009 hi there... I have been rebuilding my 1991 defender and here are the mods: - engine 3,9 V8 petrol efi from a discovery s1 (old engine was 2,5 L petrol) - gearbox LT77 (kept the old gear box but modified to handle V8) - transfer case ratio changed to 1,41 (old ratio was 1,67) - tires 235/85/16 mud tires on 6,5" standart defender rims here comes my questions: 1) Is there anyone who has a vehicle with similar to mine whom I can exchange experiences with? 2) I am not entirely happy with speed/rpm values... It does 100 km at about 3000 rpm on the 5th gear and I think I can do this at lower rpm if I change tc ratio to 1.22 If I change my tc ratio to 1.22 would my first gears effected very badly? 3) I was also told that if I put bigger tires than 235/85/16 this would help my initial problem and I would not need to change tc ratio.. what is the biggest tires / size I can use? thanks in advance naci doganci istanbul Turkey Quote Link to comment Share on other sites More sharing options...
rusty_wingnut Posted January 21, 2009 Share Posted January 21, 2009 i think a 1.22 would be a very good ratio as you've got a bit more grunt than a Tdi to pull it. Quote Link to comment Share on other sites More sharing options...
Pete Attryde Posted January 21, 2009 Share Posted January 21, 2009 You can do either to raise you gearing. The 1.2:1 Transfer box will raise the gearing by approx 15%. over the 1.4:1 transfer box. Going to a larger tyre say a 255/85/16 would raise the gearing by a smaller amount. However I suspect that 6.5" width rim would be to narrow for a 255 tyre. I think that a 33" diameter tyre is about as big as is sensible on a standard axle before you risk breaking things. Pete. Quote Link to comment Share on other sites More sharing options...
Yostumpy Posted January 21, 2009 Share Posted January 21, 2009 Standard defender rims. if steel, are only 5.5", the wolf or 1 ton rims I believe are 6.5". Some say you shouldn't even put a 235/85 on a 5.5" rim. Not all tyre fitters will do it. Quote Link to comment Share on other sites More sharing options...
headhunter Posted January 21, 2009 Share Posted January 21, 2009 A 6.5" rim fitted with a 255 tyre is permitted by BF Goodrich in their guidelines, but I have heard of some tyre fitters discouraging it. John Quote Link to comment Share on other sites More sharing options...
western Posted January 21, 2009 Share Posted January 21, 2009 6.5 Rim with 255's is the minimum size of rim for those width tyres. Quote Link to comment Share on other sites More sharing options...
nas90 Posted January 21, 2009 Share Posted January 21, 2009 hi there...I have been rebuilding my 1991 defender and here are the mods: - engine 3,9 V8 petrol efi from a discovery s1 (old engine was 2,5 L petrol) - gearbox LT77 (kept the old gear box but modified to handle V8) - transfer case ratio changed to 1,41 (old ratio was 1,67) - tires 235/85/16 mud tires on 6,5" standart defender rims here comes my questions: 1) Is there anyone who has a vehicle with similar to mine whom I can exchange experiences with? 2) I am not entirely happy with speed/rpm values... It does 100 km at about 3000 rpm on the 5th gear and I think I can do this at lower rpm if I change tc ratio to 1.22 If I change my tc ratio to 1.22 would my first gears effected very badly? 3) I was also told that if I put bigger tires than 235/85/16 this would help my initial problem and I would not need to change tc ratio.. what is the biggest tires / size I can use? thanks in advance naci doganci istanbul Turkey mmmmmmmmmmmmmmmmmm.................... 3.9 V8, just the job My nas had 1.22 ratio transfer box and my 3.9 V8 with ZF 4 speed auto was a bit gutless towing a heavy trailer so I switched to 1.41 which gives me more revs for the same speed and made a big difference to the top gear pulling power and made no difference whatsoever to the fuel economy, if you can call a V8 economy I run 255/85/16 BFG Muds so these are 33 inches diameter with a 1 inch suspension lift. With a 5 speed manual box you will probably not see the same problem as my auto, I would run the vehicle and change later especially if you are using 235/85/16 which are just under 32 inches diameter. BTW welcome to the forum just ignore the jibes from the diesel boys Quote Link to comment Share on other sites More sharing options...
A Twig Posted January 22, 2009 Share Posted January 22, 2009 I changed my Xfer box to 1.2, and have bigger tyres than you on my 300tdi. It's a bit gutless going up hills, but the fuel economy is much better! With the V8 you should be fine I reckon. Quote Link to comment Share on other sites More sharing options...
naci Posted January 23, 2009 Author Share Posted January 23, 2009 dear all, thanks very much for your comments... I think I'll go for 1:22 TC just to see the difference if any...If I like it I'll keep it, if not I!ll go back to 1:41..If I am to change the setup in the future and go for bigger tires upto 35" , hd arms, shafts etc then I may go back to 1:41 or even 1:67 gearing... I m not worried about fuel economy much because I run both my landies on LPG, my disco ( 3,9 V8 efi auto, 29"tyres) consumes about 20-22 lt lpg / 100 km in the city and a bit less on motorways... defender does more or less the same figures as the disco... both cars put a big smile on my face each time I touch the throttle so never mind the rest, life is too short to worry... thanks again an best regards... Quote Link to comment Share on other sites More sharing options...
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