Shimano RD-7400 rear mech question

Hi...Can some one help me?....Just bought on ebay a Dura-Ace rear mech...for £19...i asked the seller...7, 8 or 9 speed and his reply was 8 but could work on 9...fair enough...then i find when i get it is a a pre 1997...RD-7400...which according to Velobase is a 6 speed unit......So can i use it in either a 7 or 8 speed set up?....I have searched the net and cannot get a definitive answer...I have looked up Sheldon Brown too....If yes....what shifters will i need to get...will it have to be DA or can i use other Shimano shifters.......or has the seller misled me?...Should i just relist it on ebay......cheers....Leon

Hi Marxist, sticking my neck out without doing the research to back it up, but, I think velobase is wrong. A 6 speed dura-ace unit would be well old and even 9 speed has been around a good few years now. If it is an 8sp dura-ace I've found that generally shimano build quality at that level will work just fine on 9sp system.

I stand corrected, too quick to gob off, again.
Velobase says that the 7400 went thru a number of incarnations, from 6 (circa 1985) thru to 8sp (1998). Still if it is an 8sp mech in good nick, it should still be fine.

Hi... i agree with pbr... history lessons avaiable at http://www.dura-ace.com

Thanks for the advice...but...and i have checked with dura-ace.com...7400 group went a few changes....my RD is the first generation...ie 6 speed...RD-7401 was 7 speed and RD-7402 was labelled 8 speed...9 speed did not arrive until 1997.....I know the RD is 'dumb'.....what is important is the shifter-cassette combo.....7-7 or 8-8 0r 9-9......but both Sheldon and Velobase argue that i would need a Dura-Ace 6 speed shifter...unless i use a special routing into the RD.....Which seems a big fuss and perhaps i should stick with my 105 6/7 speed RD.....or can i mate the RD-7400 with any Shimano shifter to give smooth indexed gear changes?

I've found that 7-8 speed shifter/cassette combos work fine. They basically just added another sprocket on the back of the 7sp cassette, then adjusted the witdth of the freehub carrier to suit. Not a lot of development required to get the extra gear. 9-9 only though, same again for 10sp. Different index/sprocket spacing in order to get the extra gears.

Why not just give it a go as you've got the mech anyway.

Thanks PBR.....but just to ask [cos i am dense].....Can I use any shifter...or must i use a DA shifter.....9 is the only one commonly available.....However i found on the bay a DA 7 speed lever from the USA which would do it quite nicely as 7 speed is my objective at the mo!

Pretty sure you don't need a DA shifter specifically. Although if the RD is only 6sp perhaps you won't be able to index onto each of the 7 sprockets and the highest or lowest will cause you some problems. I did a quick bit of searching and don't think you will be able to index shift with a 7spd shifter but should be able to friction shift.

Like PBR said, if you have the mech and existing 7spd shifter spend an hour or so playing around and see what happens.

would the jockey wheels on a 6speed be wider than 7/8?
i dunno if this would be a factor with your set-up?

At present i have a 105 speed shifter!