Rutty Posted November 9, 2023 Share Posted November 9, 2023 My Mk1 2L O/D Vitesse diff is getting to the point of needing to be replaced, it currently has a 3.89 diff which is correct for the car but I was thinking of putting in a 3.63 diff to give it longer legs on motorway driving but was wondering how much it would knock down performance. Looking at the MintyLamb web site at 70 mph a 3.63 would drop the Rpm by 221 which in my mind is not going to take to much off the performance. Has anyone got any thoughts or experience they can share. Mark 1 Quote Link to comment Share on other sites More sharing options...
Rubce Posted November 9, 2023 Share Posted November 9, 2023 I am interested in doing the same mod to our Mark 3 GT6. Regards Bruce 1 Quote Link to comment Share on other sites More sharing options...
Tim Bancroft Posted November 10, 2023 Share Posted November 10, 2023 From my experience, the 3.63:1 Spitfire diff is the best diff ratio I have fitted to my GT6. The car was a non overdrive version when I purchased her, the fitting of the 3.63:1 diff and a J type overdrive have been a massive benefit. 3 Quote Link to comment Share on other sites More sharing options...
iani Posted November 10, 2023 Share Posted November 10, 2023 Another vote for the 3:63 diff here, I use one in my GT6 with a Sprint J-type OD, a great combination. 1 Quote Link to comment Share on other sites More sharing options...
mikeyb Posted November 10, 2023 Share Posted November 10, 2023 Yes agreed, common upgrade for GT6 so Vitesse should be much the same 1 Quote Link to comment Share on other sites More sharing options...
glang Posted November 10, 2023 Share Posted November 10, 2023 10 hours ago, Rutty said: My Mk1 2L O/D Vitesse diff is getting to the point of needing to be replaced, it currently has a 3.89 diff which is correct for the car but I was thinking of putting in a 3.63 diff to give it longer legs on motorway driving but was wondering how much it would knock down performance. Looking at the MintyLamb web site at 70 mph a 3.63 would drop the Rpm by 221 which in my mind is not going to take to much off the performance. Has anyone got any thoughts or experience they can share. Mark Wow Im surprised you want to go that fast on motorways as I find the wind noise of my Vitesse prohibitive! I would have thought the OD sufficient to keep the revs low enough at any comfortable cruising speed... The main issue for me changing the diff ratio (and I dont have OD) is that I wouldnt be able to toodle round town in 4th as I currently do. I find this really good for extending gearbox life and also a relaxing way to drive. Quote Link to comment Share on other sites More sharing options...
Velocita Rosso Posted November 10, 2023 Share Posted November 10, 2023 No problem in converting to 3;63, it will give you ,as you say, longer legs. I have one in the Spitfire and was the best thing done, which allows me to keep up with the `big sixes` 1 Quote Link to comment Share on other sites More sharing options...
Rutty Posted November 10, 2023 Author Share Posted November 10, 2023 5 hours ago, glang said: Wow Im surprised you want to go that fast on motorways as I find the wind noise of my Vitesse prohibitive! I would have thought the OD sufficient to keep the revs low enough at any comfortable cruising speed... The main issue for me changing the diff ratio (and I dont have OD) is that I wouldnt be able to toodle round town in 4th as I currently do. I find this really good for extending gearbox life and also a relaxing way to drive. We obviously have very different driving styles, toodling around is something I most definitely do not do, the day I do start toodling around hopefully someone will shot me and put me out of my misery. 70 or faster is regularly archived not just on motorways, yes the wind can be a bit of a problem at higher speeds but that’s what ear plugs are for and over the summer I picked up a wind deflector for £25 which has transformed the Vitesse. As for extending the life of the gearbox, the joy of the Vitesse is its a sports car even if it doesn’t look like one, that’s why the Vitesse has a close ratio gearbox, hence it is driven like a sports car hard and when parts break they get repaired which is another joy in its self. When I drive I drive to have fun whether it’s in my classics or moderns not to relax. Quote Link to comment Share on other sites More sharing options...
glang Posted November 10, 2023 Share Posted November 10, 2023 Hmmm the speed limit in towns is 30mph or lower so pootling is exactly what you should be doing! Then one of the Vitesse benefits is its relatively high and wide torque band so theres no need to be constantly switching gears. I think you have the wrong car if you want to race around.... Quote Link to comment Share on other sites More sharing options...
Rutty Posted November 10, 2023 Author Share Posted November 10, 2023 3 minutes ago, glang said: Hmmm the speed limit in towns is 30mph or lower so pootling is exactly what you should be doing! Then one of the Vitesse benefits is its relatively high and wide torque band so theres no need to be constantly switching gears. I think you have the wrong car if you want to race around.... 3 minutes ago, glang said: Hmmm the speed limit in towns is 30mph or lower so pootling is exactly what you should be doing! Then one of the Vitesse benefits is its relatively high and wide torque band so theres no need to be constantly switching gears. I think you have the wrong car if you want to race around.... I never said I don’t stick to 30s in fact I am very diligent at sticking to 30s ask my wife, as to say because you don’t like my driving style I have the wrong car I is rather arrogant. I could throw the same comment back at you and say you should have a herald if all you want to do is tootle around. 1 Quote Link to comment Share on other sites More sharing options...
glang Posted November 10, 2023 Share Posted November 10, 2023 Its only my opinion because theres far more suitable cars for racing and driving hard with numerous gear changes and also others much better for high speed cruising. Above I did say 'toodle in town' outside of that I like to use the Vitesse torque to get a move on preferrably using country A roads. I remembered why the Vitesse ended up with a 'close ratio' gearbox - not for sportiness but because the engine torque is that high a low first gear would be practically redundant. Triumph actually suggested using 2nd gear for all pull aways other than steep hill starts.... Quote Link to comment Share on other sites More sharing options...
Velocita Rosso Posted November 10, 2023 Share Posted November 10, 2023 No one mentioned `racing around` but club Triumph do endurance events where a top speed/lower rev/higher torque is needed eg Ten Countries etc....so a better diff does help 1 Quote Link to comment Share on other sites More sharing options...
Nick Jones Posted November 10, 2023 Share Posted November 10, 2023 3.63 is the diff Triumph should have put in the Vitesse 2L from the factory. Shockingly under geared as standard, especially without OD. GT6 also benefits, though really could do with a taller one, even with OD. 2 Quote Link to comment Share on other sites More sharing options...
GT64fun Posted November 11, 2023 Share Posted November 11, 2023 I run a 3.27 in my GT6. It was orginaly a non OD car, but converted by me in the late 1970s using an overdrive box from a scrapyard Vitesse. I did try a 3.63 for a while, but reverted to the 3.27. 70mph is 2800rpm in OD top. 1 Quote Link to comment Share on other sites More sharing options...
daver clasper Posted November 12, 2023 Share Posted November 12, 2023 On 10/11/2023 at 20:21, Nick Jones said: GT6 also benefits, though really could do with a taller one, even with OD. Is that compared to Vitesse Nick, as GT6 cut through the air better at higher speeds?. My Vitesse had a retro fitted overdrive and 3:27 fitted when I bought it. No problem with hill starts, acceleration probably not too perky due to diff ratio, though great cruiser in overdrive and pulls up long motorway inclines no problem. 1 Quote Link to comment Share on other sites More sharing options...
glang Posted November 13, 2023 Share Posted November 13, 2023 Can you still pottle around town in 4th Dave or does it need 3rd? Quote Link to comment Share on other sites More sharing options...
Tim Bancroft Posted November 13, 2023 Share Posted November 13, 2023 Cannot believe we are arguing about this, the 3.63:1 diff is the best compromise for a car to have reasonable acceleration and cruising speed. My GT6 was a non overdrive model when purchased in 83, 3.27:1, not great as it blunted the acceleration of what is a sports car. Have had a 3.63:1 coupled with J type overdrive in her for 35 years now, by far the best compromise. If a 2.5L car, then a 3.27:1 might be a realistic option, but aren't the carriers week and therefore susceptible to failure due to torque? 1 Quote Link to comment Share on other sites More sharing options...
Clive Posted November 13, 2023 Share Posted November 13, 2023 10 minutes ago, Tim Bancroft said: If a 2.5L car, then a 3.27:1 might be a realistic option, but aren't the carriers week and therefore susceptible to failure due to torque? Yes. I have direct experience of this. I broke several 3.27 diffs in my 2.5 vitesse. I then fitted a 3.63 which handled the abuse it was given with no further issues. That diff later went into my zetec spitfire, and when removed was still in perfect condition. It was resealed and now lives in Belgium. On my 1600 Vitesse I have swapped the original 4.11 diff for a 3.89. A good compromise as a 3.63 would probably be a bit of a stuggle. Quote Link to comment Share on other sites More sharing options...
glang Posted November 13, 2023 Share Posted November 13, 2023 1 hour ago, Tim Bancroft said: Cannot believe we are arguing about this, the 3.63:1 diff is the best compromise for a car to have reasonable acceleration and cruising speed. No arguments here just sharing thoughts n experiences as originally requested by Mark👍 Quote Link to comment Share on other sites More sharing options...
daver clasper Posted November 14, 2023 Share Posted November 14, 2023 On 13/11/2023 at 07:43, glang said: Can you still pottle around town in 4th Dave or does it need 3rd? On a strait,ish, flat,ish road it feels ok at 30mph in top, though generally in towns I use 3rd. As Glang commented, I was just sharing my experience. It was what came with the car and not saying it is anyway it the best configuration. I assume there may be some subjectivity in this anyway, depending on driving style etc Quote Link to comment Share on other sites More sharing options...
daver clasper Posted November 14, 2023 Share Posted November 14, 2023 Also, I have no experience of driving other Vitesse's, so I can't compare Quote Link to comment Share on other sites More sharing options...
Steve P Posted November 14, 2023 Share Posted November 14, 2023 My Vitesse has a 3:27 with a stronger carrier a la Mike Papworth.It also has a tuned 2.5 with a saloon box , j type OD and CV conversion. I think its a great combo as you can pootle if you wish but there is a ton of grunt on tap if you want it. I blatted it down the Staines bypass once with a Jag XF behind me, when we pulled up at the traffic lights he wound his window down and said to me "you must have a V8 in that". S Quote Link to comment Share on other sites More sharing options...
Tim Bancroft Posted November 15, 2023 Share Posted November 15, 2023 Ah, Staines by pass, the scene of my last diff explosion.....3.63 let go! The car had just done about 3 autosolos and the diff was very tired, I have the pinion gear somewhere! Quote Link to comment Share on other sites More sharing options...
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