Question about 2002 Triumph Triumph Thunderbird

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6th gear modification

Hi all. Has anyone out there replaced their 5-speed transmission with a 6-speed? I'm torn on whether to make this conversion on my '95 Tbird. I need your help to figure this out quick, while my mechanic still has my tranny out of the bike (damn you, sprag clutch!). With a 6-speed, are the ratios the same for 1-5, and the sixth purely an overdrive gear, or do the top and bottom ends of the gear range stay basically the same, with smaller intervals between? The main thing I'd hope for out of a sixth gear is improved gas mileage. (I currently average about 36mpg) Did you get a boost in mpg after your conversion? How much? Any other performance considerations? With parts ($425) and labor ($100) this conversion is not something I can easily afford on top of the other work being done, but now would be the time to do it. Thanks for your input!

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Sixth Gear is an additional ratio. The five speed bikes have a spacer on the shaft instead of the sixth gear, so the conversion is not so difficult for someone who knows what they are doing. The shifter drum also needs to be changed. I've not done the conversion, but I have one six speed bike and one five speed bike. Sixth gear is nice for highway use. In reality it only changes RPM at 70 mph by about 500 revs. But that is enough to make cruising at higher speeds a little more relaxed. Is it necessary? Hmmm, I guess that depends on how much time you spend cruising on the Interstates. Personally I avoid Interstates most of the time, so I find it not much of a problem. Good luck with your decision, and you are right now is the time to do it if you are going to.

Posted on Nov 10, 2008


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