NDP Posted May 2 Report Share Posted May 2 Hopefully someone from the technical side can help me with this. Some time ago I purchased a 3.27 diff for my Triumph GT6. I was going to get it refurbished and put onto my car, which would bring it back to original. However, I now realise the diffs fall into two categories, up to KE/KF200000 and above. My GT6 fits into the "up to KE/KF 200000" category but I have no idea which category my purchased diff belongs to. So my questions are: 1). Is there an easy way to identify which category my diff belongs to? 2). Would it cause problems if the diff was a KE/KF 2000001+ diff and I had it fit to the car? Any help / pointers much appreciated. Link to comment Share on other sites More sharing options...
Colin Lindsay Posted May 3 Report Share Posted May 3 I'll take a guess that it's to do with the rear suspension ie the earlier case was for rotoflex and after 20000 was for swing spring, so the number of studs on top of the case varies - six for the fixed spring and four for the swing. All else is probably the same, but I'm open to correction and enlightenment on that! Link to comment Share on other sites More sharing options...
johny Posted May 3 Report Share Posted May 3 The jury is out on whether its safe to use a 4 hole case on a fixed spring as it might apply more stress to the fixings... Link to comment Share on other sites More sharing options...
NDP Posted May 3 Author Report Share Posted May 3 Would it be problematic to fit a six stud case to a rotoflex car?. Why I ask is because prior to owning the car the original 3.27 was replaced by a 3.66 I believe. I am in the process to installing a 3.27 taking it back to originality and then came across the two types. Hence the issue I have. Advise from anyone with any knowledge in this are would be much appreciated (including where I may be able to contact you directly for a chat about the issue). Kind regards. Link to comment Share on other sites More sharing options...
Puglet1 Posted May 3 Report Share Posted May 3 I have just fitted a modified 4 hole diff to my vitesse roto. I placed a 6 holed top spring plate onto the 4 holed diff and used a cordless drill to drill the extra 2 holes. If you go this route, measure the depth of the original holes in the casing otherwise it’s easy to drill straight through it. Link to comment Share on other sites More sharing options...
johny Posted May 3 Report Share Posted May 3 Six stud is the correct one for rotaflex Link to comment Share on other sites More sharing options...
Colin Lindsay Posted May 3 Report Share Posted May 3 You can swap the case without affecting any of the torque settings or 'fine tuning'; all the intricate bits are in the front part. If you already have a six-stud case spare, then just drain the oil, remove the two inner axles by undoing four allen keys and withdraw, undo the bolts all the way round the case, and remove the rear part. You'll need a new gasket (fiddly to fit and often tear) but it should be a straight swapover. The rear cases are nearly all identical bar the very early versions. Replace the rear bushes at the same time, it saves trouble later. Link to comment Share on other sites More sharing options...
johny Posted May 3 Report Share Posted May 3 I would say only replace rear bushes if really shot as they can look ugly but last longer than some replacements? Link to comment Share on other sites More sharing options...
Colin Lindsay Posted May 3 Report Share Posted May 3 2 hours ago, johny said: I would say only replace rear bushes if really shot as they can look ugly but last longer than some replacements? I went for the super-duper blue Polybushes; no idea if they're superior but the colour is nice... Link to comment Share on other sites More sharing options...
Steve P Posted May 3 Report Share Posted May 3 I have a 3:63 in my 1500 Herald which I am about to do a CV conversion on, it has a 4 stud casing. Also fitting a Courier spring with lowering block, was wondering about the suitability of only 4 studs. S Link to comment Share on other sites More sharing options...
Colin Lindsay Posted May 3 Report Share Posted May 3 26 minutes ago, Steve P said: I have a 3:63 in my 1500 Herald which I am about to do a CV conversion on, it has a 4 stud casing. Also fitting a Courier spring with lowering block, was wondering about the suitability of only 4 studs. S Any fixed spring, I'd go for six. I only used four on swing spring, obviously because I had to. Link to comment Share on other sites More sharing options...
Iain T Posted May 3 Report Share Posted May 3 2 hours ago, Colin Lindsay said: went for the super-duper blue Polybushes; no idea if they're superior but the colour is nice... Hardy Engineering who fitted a refurb diff in my Vitesse advised against fitting the Supaflex poly bushes I supplied as their customers reported they transfer too much vibration to the chassis. But then most things jiggle about on a Triumph small chassis! Link to comment Share on other sites More sharing options...
Colin Lindsay Posted May 3 Report Share Posted May 3 55 minutes ago, Iain T said: Hardy Engineering who fitted a refurb diff in my Vitesse advised against fitting the Supaflex poly bushes I supplied as their customers reported they transfer too much vibration to the chassis. But then most things jiggle about on a Triumph small chassis! This is the great problem: trying to strike a balance between durability and direct feeling of the drive experience, and feeling every bump and rumble in the road - hence the fact that I use poly steering bushes, not alloy. I was never a fan of red Polybushes bar in radius arms, but in my GT6 and since then, all my Heralds I bought complete sets of very hard yellow nylon-like bushes for the suspension from an online seller (Kevin?) and these have been superb; no noticeable road noise but very direct steering and suspension. I bought three sets and just recently used the last of them, and then went for the orange Superflex type on my 13/60 - personal preference only, but I do like them, if only for the bling factor compared to original rubber bushes (which may not be the same quality these days). The 1200 Estate diff got blue rear bushes and uprated black fronts, but the 13/60 got orange all round, and I've not noticed any problems, in fact the 13/60 is too quiet and I'm always wondering what's wrong... Link to comment Share on other sites More sharing options...
Iain T Posted May 3 Report Share Posted May 3 (edited) 45 minutes ago, Colin Lindsay said: bought complete sets of very hard yellow nylon-like bushes for the suspension from an online seller (Kevin?) Kevin the yellow Minion? It could have been Doug he likes bright yellow..... On a serious note the variations of rubber/poly bushes can dramatically change the ride and handling. With the bushes fitted by Hardy the transfer of vibration is much less than before and makes for a noticeably smoother ride. I hope they last🤞 Edited May 3 by Iain T 1 Link to comment Share on other sites More sharing options...
johny Posted May 3 Report Share Posted May 3 Think we're getting confused here. Rotaflex is a fixed spring not a swing spring so should have a diff with six hole fixing.... Link to comment Share on other sites More sharing options...
NDP Posted May 3 Author Report Share Posted May 3 3 hours ago, chrishawley said: No. It would not be problematic. All it would mean is that there would be two unsed holes. Considering pre to post 20k vehicles the output flanges are the same. One wrinkle might be the input flange. AFAIK the flange dimensions are all the same for the vehicle consioidered here (roto GT6, non-roto GT6 and Spit 1500). But this would be worth a check before fitting up. Retro fitting a post20k diff to a roto GT6 might be viewed more circumspectly but since that's not the question I'll leave it alone. Actually the retro fitting of a post 20k diff to a Roto GT6 could quite possibly be the exact problem here. I know the 3.27 diff has 6 stud holes. Does that definitely make it a post 20K diff? If so my GT6 (1972) is a pre 20K vehicle. Johny seems adamant that the 3.27 diff for a Rotoflex should have six holes. Looks like this problem is set to rumble on. Any more input chaps? Link to comment Share on other sites More sharing options...
KevinR Posted May 4 Report Share Posted May 4 On the production line, excessive numbers of 6 stud diff casings were converted to 4 stud ones by fitting a pair of cut off studs. likewise, it’s possible that a previous owner of the diff has already fitted a 6 stud casing. As previously mentioned in this thread, it’s also possible to drill and tap the two extra holes needed to convert a genuine 4 stud casing into a 6 stud one Link to comment Share on other sites More sharing options...
chrishawley Posted May 4 Report Share Posted May 4 I deleted my entry since I took one bit of ambiuity and amplified it with greater ambiguity. Apols! May I have another go? Up to 20K: 6-stud unit and fixed spring (= rotoflex) Post 20k: 4-stud unit and swing spring (= non-rotoflex) Thus • a 6-stud unit fits all, without modification. • a 4-stud unit being fitted with a fixed spring would need to be modified to have six studs. In case I make an error again could that be confirmed/disconfirmed? Link to comment Share on other sites More sharing options...
johny Posted May 4 Report Share Posted May 4 Ha we're getting there, just one last bit of the puzzle. 3.27 ratio diffs were used in all models of GT6 without OD (some did have it even with OD) and they came with 6 and 4 hole casings depending on fixed or swing spring back axle. Link to comment Share on other sites More sharing options...
NDP Posted May 13 Author Report Share Posted May 13 Thanks guys Link to comment Share on other sites More sharing options...
johny Posted May 13 Report Share Posted May 13 I see this has been a very long road so are you finally cruising with a 3.27 ratio diff now? Link to comment Share on other sites More sharing options...
NDP Posted July 21 Author Report Share Posted July 21 Sadly no. A new leaf spring from Owen Springs fitted along with the 3.27 refurbished diff and new orange bushes. Going around corners and now and again when the engine is under load is worrying. There is a grinding noise coming from the rear of the car. Quite noisy. It is going back the the mechanic when he next has a slot to investigate. Any ideas chaps? Link to comment Share on other sites More sharing options...
Pete Lewis Posted July 21 Report Share Posted July 21 have you checked its not tyres fouling on the wing flange lip ??? there is nothing in the diff or spring or suspension that makes agrinding noise on corners so it sounds like tyre contact with body roll Pete Link to comment Share on other sites More sharing options...
NDP Posted July 21 Author Report Share Posted July 21 Cheers Pete, I will ask the mechanic to take a look at that as well. Link to comment Share on other sites More sharing options...
dougbgt6 Posted July 22 Report Share Posted July 22 On 03/05/2024 at 15:30, Iain T said: Kevin the yellow Minion? It could have been Doug he likes bright yellow..... Nah, my polybushes are blue, rules out the Russian road trip I was planning, a lady has just got 6 years jail for wearing yrllow and blue shoes in the glorious federation. Doug Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now