johny

Dont entirely agree there Nick, maybe the Mk2 Vitesse with a bit more power can pull a higher ratio but in my Mk1 I find the 3.89 pretty good. It depends on your driving style and roads I suppose but for me 60 - 70mph is enough and its not mechanical but wind noise (plus handling) that limits me more and thats in a fixed head! True first gear could be taller but I love the acceleration in the other gears and then using 4th for everything else.....

I dont know where youre getting your info from Steve but it was definitely: Mk 1 and 2 Vitesse 2000 (both with or without OD) = 3.89:1 As you say theres often many different opinions so trying stuff out is the only way to know and yes is all part of the fun! Dont worry though if you dont like the 3.27 unit it'll be easy enough to sell.....

Hi Darren, it means what Paul put here although to be entirely correct Spitfires, logically, also used the 150328 in their 3 rail 4 synchro boxes at around the same time as the GT6 III and Dolly 1850 before all models went over to single rails....

even more interesting as the 3.27 ratio was never used in the Vitesse which had a standard of 3.89. Your ratio was only used in the lighter GT6 and then only if it didnt have overdrive so its the rarest of the ratios. Is your engine standard? I still have the original diff in my non overdrive Vitesse which I like but would consider going to a 3.63 only if I can go up the steepest main roads without having to drop a gear (I think doing this too often would rapidly finish off my gearbox!)

Did you have new valves installed? I come from a heavy engineering background and one thing we always consider when planning to overhaul machinery is the risk of actually making things worse! Any new component used can be faulty and, in this case, the valve could have had a manufacturing defect that caused it to fail. Another possibility is that an error is made in the installation work such as leaving too tight a tolerance between valve and guide so that in operation it seizes however here I wouldnt have expected the valve to break.....

Hi Steve, looks like you might have put a 3.63 diff in your Vitesse. If so how is it compared with the original in particular whats the pull away like in first gear and can you maintain fourth on the steepest of inclines?

Correct Paul, that seems to be the current understanding?

Thanks Paul. Yes the later type obviously have more surface area for gripping and synchronising plus theres no way theyre interchangeable!

It is a bit confusing but I believe the earlier 148409 was used in both 3 and 4 sync 3 rail boxes (for example GT6 1 & 2 and Vit 1 & 2). Then the 3 rail box was modified in various ways (presumably all mods at the same time?) and 150328 ring (150326 is a digit out Pete) was used from then on including the single rail units. I think all use just one type of ring or the other and theyre shouldnt be interchangeable although sometimes they do turn up in the wrong places and it would be interesting to know how well those boxes functioned......