Rubce Posted November 27, 2021 Share Posted November 27, 2021 Hi All I am considering fitting a 3.27 diff to our Mk3 GT6 to reduce engine revs. The car has a 2 litre engine, 4 speed box with overdrive. Can anyone advise from previous experience on this configuration? Thanks in anticipation Bruce Quote Link to comment Share on other sites More sharing options...
Clive Posted November 27, 2021 Share Posted November 27, 2021 Shouldn't be an issue. It will be like a std non-od GT6, but with the addition of OD. It means you may need to flick out of OD sometimes, but is very relaxed for motorway. It may not make much difference to economy, unless you have a very light foot (heaven forbid) The other alternative is to use a 3.63 diff from a spit 1500. Halfway between a 3.89 and 3.27, a lot easy to come by, and stronger. Andy Cook has this combo (and many other GT6 owners) so do consider it. 1 Quote Link to comment Share on other sites More sharing options...
Rubce Posted November 27, 2021 Author Share Posted November 27, 2021 Hi Clive. Thanks for the quick reply and the suggestion regarding a 3.63 I have a 2.5 litre engine stashed in the garage which will be going into the car at some point in the future. Why is the 3.63 considered stronger than the 3.27? Load stresses? Regards Bruce Quote Link to comment Share on other sites More sharing options...
Clive Posted November 28, 2021 Share Posted November 28, 2021 7 hours ago, Rubce said: Hi Clive. Thanks for the quick reply and the suggestion regarding a 3.63 I have a 2.5 litre engine stashed in the garage which will be going into the car at some point in the future. Why is the 3.63 considered stronger than the 3.27? Load stresses? Regards Bruce The internals are different. I think there may possibly be a variation within the range of 3.27s, and the dolly 1850 auto was the last, so strongest? you would really need to check with somebody like Peter Cox or Mike Papworth. I had a 2.5 vitesse, fitted with a 3.27. It used to get through them, after 4 breaking, I fitted a 3.63, and that survived, went into my zetec spitfire, and the next, and now lives in Dirks spitfire (checked before it went to Dirk, all was well, just fresh seals as a matter of course) 1 Quote Link to comment Share on other sites More sharing options...
mblowing Posted November 28, 2021 Share Posted November 28, 2021 12 hours ago, Rubce said: Hi All I am considering fitting a 3.27 diff to our Mk3 GT6 to reduce engine revs. The car has a 2 litre engine, 4 speed box with overdrive. Can anyone advise from previous experience on this configuration? Thanks in anticipation Bruce Hi Bruce I have this in my 2.5 pi spitfire with a 28% overdrive works really well , I can’t see why in your car why it wouldn’t be similar 1 Quote Link to comment Share on other sites More sharing options...
docwad Posted November 28, 2021 Share Posted November 28, 2021 Hi both my gt6s Inc current mk1 have run this combination, OK it may not be fastest off the mark, but is v relaxed motorway cruising and the 2l lump is v capable of pulling this. I easily keep up with tr6,s and it s as fast as my pi. Ratio is 25 mph per 1000 rpm in od and 20mph per 1000 in top. I'm sure thus would have been a more standard fit if more motorways were around and Stanley markland wasn't, hiding in the wings with his pull from 10mph in top gear without hesitation bull! 1 Quote Link to comment Share on other sites More sharing options...
Tim Bancroft Posted December 28, 2021 Share Posted December 28, 2021 Hi Bruce, I have driven my GT6 with J type overdrive and 3.63:1 differential for over 30 years and found it to be the ideal gearing for the car, decent enough engine speed at motorway speeds and nippy enough when pulling away. My GT6 is a non overdrive model and therefore had a 3.27:1 ratio diff, awful gearing for getting away quickly, much better now with the o'd and 3.63. 1 Quote Link to comment Share on other sites More sharing options...
Rubce Posted December 28, 2021 Author Share Posted December 28, 2021 On 28/11/2021 at 19:57, docwad said: Hi both my gt6s Inc current mk1 have run this combination, OK it may not be fastest off the mark, but is v relaxed motorway cruising and the 2l lump is v capable of pulling this. I easily keep up with tr6,s and it s as fast as my pi. Ratio is 25 mph per 1000 rpm in od and 20mph per 1000 in top. I'm sure thus would have been a more standard fit if more motorways were around and Stanley markland wasn't, hiding in the wings with his pull from 10mph in top gear without hesitation bull! Hi Doc Just to clarify, you have a 3.63 or a 3.27 diff fitted? Regards Bruce Quote Link to comment Share on other sites More sharing options...
Rubce Posted December 28, 2021 Author Share Posted December 28, 2021 39 minutes ago, Tim Bancroft said: Hi Bruce, I have driven my GT6 with J type overdrive and 3.63:1 differential for over 30 years and found it to be the ideal gearing for the car, decent enough engine speed at motorway speeds and nippy enough when pulling away. My GT6 is a non overdrive model and therefore had a 3.27:1 ratio diff, awful gearing for getting away quickly, much better now with the o'd and 3.63. Hi Tim Thanks for the advice. Looks like I will on the look out for a good condition 3.63. Regards Bruce Quote Link to comment Share on other sites More sharing options...
Tim Bancroft Posted December 29, 2021 Share Posted December 29, 2021 Getting difficult to find, Mike Papworth or Dave Pearson would be a good first try. They seem to occasionalyy come up on ebay, but of course unwarranted condition. 1 Quote Link to comment Share on other sites More sharing options...
mikeyb Posted December 29, 2021 Share Posted December 29, 2021 I have a 3:63 in my Mk1, a few years ago I took 3 or 4 tired diffs to Mike Papworth, he pulled all the good bits and made me up a 3:63 and a 3:27. Not tried the 3:27 yet bur the 3:63 works well, apart from I cannot find a stock speedo with the correct gearing so the speed indication is well out! 1 Quote Link to comment Share on other sites More sharing options...
Velocita Rosso Posted December 29, 2021 Share Posted December 29, 2021 32 minutes ago, mikeyb said: I have a 3:63 in my Mk1, a few years ago I took 3 or 4 tired diffs to Mike Papworth, he pulled all the good bits and made me up a 3:63 and a 3:27. Not tried the 3:27 yet bur the 3:63 works well, apart from I cannot find a stock speedo with the correct gearing so the speed indication is well out! Like myself....the speedo works but not spot on...so I bought an electronic /digital speedo.......miles/Kms/ max speed pre programmer/tire alarm/ etc etc and that sits on the dash....all for £18.00 Saves the hassle of swapping gauges etc Quote Link to comment Share on other sites More sharing options...
mikeyb Posted December 29, 2021 Share Posted December 29, 2021 (edited) is that gps? mine is far from spot on - 20mph out at any given speed! Edited December 29, 2021 by mikeyb Quote Link to comment Share on other sites More sharing options...
Royboy66 Posted December 30, 2021 Share Posted December 30, 2021 Hey Bruce, In my Mk1 I’m running a 2.5 with j-type 28% & 3:63 diff. I find it a Great combination 👍 regards Roy ( Shropshire border control🤓) 1 Quote Link to comment Share on other sites More sharing options...
Martins Stag Posted December 30, 2021 Share Posted December 30, 2021 Roy I agree with you I ran a 1500 spitfire with a 2.5 on su's plus a 28% J type. 3.63 and 14 inch wheels too An ideal choice and stronger that the 3.27 too Martin 1 Quote Link to comment Share on other sites More sharing options...
thescrapman Posted December 31, 2021 Share Posted December 31, 2021 On 29/12/2021 at 10:14, mikeyb said: I have a 3:63 in my Mk1, a few years ago I took 3 or 4 tired diffs to Mike Papworth, he pulled all the good bits and made me up a 3:63 and a 3:27. Not tried the 3:27 yet bur the 3:63 works well, apart from I cannot find a stock speedo with the correct gearing so the speed indication is well out! Can't see the speedo being problem, they will have banned IC engines before it is on the road again, so you will need to find an electronic one to work with the batteries. Quote Link to comment Share on other sites More sharing options...
Guppy916 Posted January 1, 2022 Share Posted January 1, 2022 Happy year. Guys, when I did my mk3 I sent the speedo to speedy cables, they serviced and recalibrate it, to suit my diff and wheels Quote Link to comment Share on other sites More sharing options...
Steve P Posted January 2, 2022 Share Posted January 2, 2022 Not a GT6,but if you are planning on a 2.5 conversion,i have a tuned 2.5 in my Vitesse with a saloon o/d box and 3:27 diff,built by Mike Papworth with a stronger carrier(TR7?),i find it a great combo, too old for No.11 starts but driven enthusiastically. Steve 1 Quote Link to comment Share on other sites More sharing options...
Rick60 Posted January 2, 2022 Share Posted January 2, 2022 Like Guppy I too sent my speedo to Speeycables after fitting a 3.63:1 and had it recalibrated. They weren't very speedy! But did a great job 🙂 Quote Link to comment Share on other sites More sharing options...
Swifty75 Posted January 10, 2022 Share Posted January 10, 2022 I had a Mk2 Vitesse with a 2500 on twin SUs. It had OD and a 3.27 diff. 25 mph per 1000 rpm gave brilliant cruising on the 2016 rbrr, and good MPG. It didn’t ever feel like it struggled to pull top OD. Quote Link to comment Share on other sites More sharing options...
Spitfire6 Posted January 16, 2022 Share Posted January 16, 2022 Hi, With a 2.5EFI, I have had many 3.63 diffs go gender neutral poof. Even 3.27 is not numerically low enough for me. Going to fit taller tyres on back to lower RMP cruise speed. If I want to move quick I switch off OD or change down. Over 70 in 3rd is available. 1st is plenty numerically high enough to smoke tyres with ATB diff & 215's. Quote Link to comment Share on other sites More sharing options...
PeteStupps Posted January 17, 2022 Share Posted January 17, 2022 On 16/01/2022 at 17:10, Spitfire6 said: I have had many 3.63 diffs go gender neutral poof. Had to read this a couple of times 🧐 😄 Quote Link to comment Share on other sites More sharing options...
Gt6s Posted January 20, 2022 Share Posted January 20, 2022 On 29/12/2021 at 10:14, mikeyb said: I have a 3:63 in my Mk1, a few years ago I took 3 or 4 tired diffs to Mike Papworth, he pulled all the good bits and made me up a 3:63 and a 3:27. Not tried the 3:27 yet bur the 3:63 works well, apart from I cannot find a stock speedo with the correct gearing so the speed indication is well out! Upsize your rear tyres to the rolling eqivilent of 185/70 non OD speedo will work. Thats my mix. Quote Link to comment Share on other sites More sharing options...
mikeyb Posted January 22, 2022 Share Posted January 22, 2022 Hmmn, I think that I'm on 175/70 Quote Link to comment Share on other sites More sharing options...
Gt6s Posted January 23, 2022 Share Posted January 23, 2022 16 hours ago, mikeyb said: Hmmn, I think that I'm on 175/70 OOOOOOOOOPS ! Forgot I use a 28% overdrive as well. Gives 24 mph per 1000 rpm Quote Link to comment Share on other sites More sharing options...
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