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Cobra (Thames Ditton) Forum / Axle ratio
« on: April 05, 2016, 22:57:09 »
If we start to consider overdrives then perhaps a simpler solution is to fit a 5 speed gearbox? My (4 speed) car runs a 3.77 diff. It's noisy and thirsty but it doesn't half go. And it still has a huge first gear. John, if you fitted Salisbury's highest ratio (2.88:1) then you really gave 6011 some motorway legs. You'll know this ratio was fitted to automatic 428s (max power @ 4,600 rpm) and gave around 30 mph per 1000 rpm on 15" 205/70 tyres. Manual 428s got the 3.07:1, which gave about 27.5 mph per 1000. I have a spare 3.31 diff which I may fit at some stage, but I think it's about as low as is possible to go without making that first gear just too long to use. Contemporary road tests of COB and COX cars record that these European cars got a 3.54 diff as standard. The Motor road test of COB 6106 car talks about the standard 3.54 ratio being replaced with a 3.31 diff on subsequent cars (but looking at the figures obtained in the road test I'd make a guess that the car had a 3.77:1 fitted anyway; others will know more.) Oh, and again reading road tests of the time, it seems that 427s were fitted with a 3.54 diff as standard too. But do I want to go touring in a Cobra? Er, not really. Give me an Ace, AC or Bristol powered, any day. 5 speed gearboxes for 289 Cobras? Seems a solution?