John Griffiths Posted October 9, 2006 Share Posted October 9, 2006 Probably sounds like blasphemy to you track chaps but I was wondering whether my 1.6K SV would be better to drive on the road with a 5 speeder rather than the current 6'er which has very close ratios and not always a pleasant change quality, 1 to 2 in particular. When you've all finished laughing I would appreciate any advice. Link to comment Share on other sites More sharing options...
MartinWoodham Posted October 9, 2006 Share Posted October 9, 2006 John, you sound like a very wise man, the 5-speeder suits the cruising nature of the SV so much better. I'll happily swap my 5 speeder for your 6, I'll even offer a hand with the swap over 😬 😬 😬 Martin Aero'd Roadsports B with a garage slowly filling up with upgrade parts Link to comment Share on other sites More sharing options...
Brucey Posted October 9, 2006 Share Posted October 9, 2006 John, I thought I had the only Caterham in the village! (I'm in Saltwood). General opinion is that a 6 speed box suits a Caterham well and is a £1K+ upgrade. They can become a bit of a drag when touring as 6th is the equivilent to 4th on a 5 speed box using standard diffs. My 5 speed box is also 'notchy' until it warms up. I intend to chage to MTL oil sometime. I would also like to fit a 'long 1st' conversion as the standard Sierra ratios are more suited for towing caravans. This would give me what I consider the ideal set up for touring use for my 1400Kss. Make sure it's not a case of 'the grass is greener' before making any decisions. You are welcome to drive my car for comparison if it helps. Bruce. Link to comment Share on other sites More sharing options...
Support Team Shaun_E Posted October 9, 2006 Support Team Share Posted October 9, 2006 As I understand it the 6 speed box is normally supplied together with a 3.62 diff and the 5 speed with a 3.92. This means that the difference between the top gears is not as much as is made out and although 4th in the 5 speed is a direct drive, the same as 6th in the 6 speed, the actual mph/rpm in those resepective gears will not be the same due to the different diffs. Bunging this stuff into gearcalc with 195/55R15 tyres gives: 5speed: 21.56 mph per 1000rpm (70mph = 3246rpm) 6speed: 19.26 mph per 1000rpm (70mph = 3634rpm) If you fit a 5 speed with a 3.62 diff then you get 23.35 mph per 1000 rpm and 70mph = 2998rpm (and a theoretical top speed of 175mph ). I suggest that you a) play around with gearcalc (search on here for a link to a copy) and b) get a ride in a 5 speed box car and see if it really does make that much of a difference to you. IMHO it is wind noise that dominates once you reach motorway speeds (and I have a 6 speed, high power K and no carpets or any other form of sound deadening). Yellow SL #32 Link to comment Share on other sites More sharing options...
Allen Payne Posted October 9, 2006 Share Posted October 9, 2006 How many miles have you done? The change on six speed box is better now, after 25,000 miles, than it was when it was newly rebuilt. Link to comment Share on other sites More sharing options...
John Howe Posted October 9, 2006 Share Posted October 9, 2006 Six speed comes with either 3.6 or 3.9 ratio. If you really want to change, then you should be able to sell the six speed for £1,200-£1,500 JH Deliveries by Saffron, the yellow 230bhp Sausage delivery machine Link to comment Share on other sites More sharing options...
Andy Best Posted October 9, 2006 Share Posted October 9, 2006 The Five to Six speed was on of the best upgrades I have done on my car, I still have the old five speed diff so I really get high RPM cruising. This doesn't really bother me as the other noises by far out weigh the engine. The car is sprightly and a joy to drive through the gears, I would suggest you have the box fettled by a gear box man. Phil at Road & Race Transmissions has a good reputation in the club and when refitting fill it with Red Line MTL considered the best oil for the six speed box. If you do take the plunge and fit a five speed I will swap diffs with you 😬 Andy Link to comment Share on other sites More sharing options...
John Griffiths Posted October 9, 2006 Author Share Posted October 9, 2006 Thanks guys. "Grass is greener" really struck a chord - Bruce we must get together - my e-mail address is johnandrosemarygriffiths@btinternet.com . I was amazed at how many pieces of advice I received in such a short time, but I guess you people haven't retired yet so have not discovered what it's like to be really busy! . Link to comment Share on other sites More sharing options...
RiF Posted October 9, 2006 Share Posted October 9, 2006 I would look at a swap if you go that way. I am building a new 1.6 seven and would prefer 5 speed. Box will be new in exchange but would want more info first. RiF Flying even faster in my very bright yellow 226bhp Duratec 7, with internal kevlar/carbon panels and pushrod suspension 😬 😬 😬.for pictures of 7 and carbon Link to comment Share on other sites More sharing options...
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