AGC Posted June 20, 2015 Share Posted June 20, 2015 Hi all, I would like your thoughts please.I have a mk3 spitfire with a noisy dif. When the car was serviced recently it was suggested that if I decide to replace the dif with a rebuilt one then it would be a good upgrade to change it for a later set up, ie mk4. It was said that with the dif and rear axle upgrade this would improve handling. I am also considering exchanging the gearbox for a full syncro'd one at some stage when funds allow and adding overdrive which I don't have at the moment. However I think my decision what to do regarding the dif will need to be brought forward because it has started to leak more and its time to replace the seals. My options are to get the seals replaced on my existing dif and carry on with a fairly noisy dif or go for a replacement. If I go for a replacement ive got to decide if I stick with the original Mk3 set up or upgrade to later set up. If I stick to the existing set up and replace the dif then Ive got an identical exchange unit. If I go with the upgrade then I will have to pay the non exchange supplement. The question is what to do?? Quote Link to comment Share on other sites More sharing options...
Saltddirk Posted June 20, 2015 Share Posted June 20, 2015 Not helping I know,but the choice of a overdrive later on might also influence your choices,If you install a overdrive you might not need a longer diff. And if you have a longer diff it might be too tall for driving the Mk3 with an overdrive, would depend on the car I guess, is it standard? more ooomph?I think the original diffs are too high geared for modern traffic, hence the installation of a overdrive box on mine and in the rebuild now we have installed the slightly longer ( 3.89 as opposed to the 4.11 original) Mk3 diff.As SOD's law would have it, a few weeks after rebuilding the 3.89 with new bearings ea I was offered a used but good Mk4 diff ....Dirk Quote Link to comment Share on other sites More sharing options...
Clive Posted June 20, 2015 Share Posted June 20, 2015 This is always a tricky one. Changing the diff will make a slight difference to the revs at any given speed, use this site to see what effect various combinations have:http://www.mintylamb.co.uk/gearspeed/And you will see changing from a 4.11 to 3.89 makes little difference. Changing to a 3.63 from a 1500 will, but will make the car sluggish off the line, once going you can just stay in gear longer.Other issues include the fact your current diff uses 5/15 bolts on a different PCD from prop and shaft flanges to the other diffs. And to the handling. That has naff all to do with the diff, but changing to the later rear spring and matching front ARB will make the car much easier to get round the bends quickly and less drama. That can be done with your existing diff. (the later spring only uses 4 fixing bolts on the diff, so you just need to blank off 2 holes in yours using a short section of bolt with the head cut off)My (personal) choice on a mk3 would be keep teh 4.11 but fit overdrive, and a swingspring conversion. Secondhand conversion stuff is usually fine and much cheaper than new, plus the spring is unlikely to sag quickly like many new ones.If no od in the pipeline, a 3.63 diff and sacrifice initial acceleration (it is not really a huge issue) Quote Link to comment Share on other sites More sharing options...
Richard B Posted June 20, 2015 Share Posted June 20, 2015 Quoted from cliftyhanger My (personal) choice on a mk3 would be keep teh 4.11 but fit overdrive, and a swingspring conversion. Secondhand conversion stuff is usually fine and much cheaper than new, plus the spring is unlikely to sag quickly like many new ones.If no od in the pipeline, a 3.63 diff and sacrifice initial acceleration (it is not really a huge issue) I'm with Dirk & Clive on this. What sort of driving will you do? Blat around country lanes, dual carriage-way or motorway?A MkIV rear set up is a good package which was designed to improve the MkIII build. Swing-spring and a 3.89 diff. Personally I think the 3.63 will be too tall for a MkIII, you have still got the MkIII 1300 engine? If so don't swap it out! and if you haven't got an OD, fit that before doing any diff change. Quote Link to comment Share on other sites More sharing options...
John Bonnett Posted June 20, 2015 Share Posted June 20, 2015 On my 1500, I'm running a 3.89 diff with D type overdrive. This works very well giving about 21mph per thousand revs in overdrive fourth. I had planned on using a 3.63 diff but I'm glad I didn't because with the close ratio box first would have been too tall. Quote Link to comment Share on other sites More sharing options...
AGC Posted June 20, 2015 Author Share Posted June 20, 2015 Great replies, thank you. Really given me food for thought. I use the car for cruising around the country lanes at a sedate pace and some A road driving when I have to. Im leaning towards just having the seals replaced at the moment because its leaking quite badly and I don't want to rush to spend my money!! My heart says go the whole hog and replace the gearbox which is a bit noisy along with fit overdrive and refurbed 4.11 diff but my head is saying are you throwing too much money at this car which is probably only worth £3-4000..... 🤔 Quote Link to comment Share on other sites More sharing options...
esxefi Posted June 20, 2015 Share Posted June 20, 2015 if you like it and enjoy driving it don't worry about its value.a lot of us have spent far too much than is decent on triumphs(naughty)imo I don't think you will loose money in the long run,I see values steadily increasing although talk is of a bubble forming in the higher end classic car market.(perhaps rightly so ) Quote Link to comment Share on other sites More sharing options...
RedRooster Posted June 20, 2015 Share Posted June 20, 2015 You can never spend too much money on a Triumph ) Quote Link to comment Share on other sites More sharing options...
Sheepy Posted June 21, 2015 Share Posted June 21, 2015 You say your diff is noisy?What noise, a rumbling? A whine? Could be worth just rebuilding your diff, you are going to strip it for the seals anyway!! 😉Is it a daily driver or just a fun toy? Quote Link to comment Share on other sites More sharing options...
thescrapman Posted June 21, 2015 Share Posted June 21, 2015 The leaking might just be a blocked breather. Have you checked? Quote Link to comment Share on other sites More sharing options...
Saltddirk Posted June 21, 2015 Share Posted June 21, 2015 Quoted from cliftyhanger That can be done with your existing diff. (the later spring only uses 4 fixing bolts on the diff, so you just need to blank off 2 holes in yours using a short section of bolt with the head cut off) Dont forget to buy new bolts... 1) always a good idea when replacing suspension related parts and 2) the later bolts are longer.... Now ask me how i found out... D Quote Link to comment Share on other sites More sharing options...
AGC Posted June 21, 2015 Author Share Posted June 21, 2015 Quoted from thescrapman The leaking might just be a blocked breather. Have you checked? Cleaned all the crud and oil from the diff and thought that the leak was from the prop shaft end. I somehow managed to get my fingers on the split pin in the breather hole and found it was blocked solid with crap. managed to clean it and release the split pin. Topped up the diff with oil and took the car for a good run. That was Saturday morning and since then it hasn't lost ONE DROP if oil so the blocked breather was causing oil to be forced past the prop seal.The breather is a bugger to get to so I can see why its probably never been cleaned. Quote Link to comment Share on other sites More sharing options...
AGC Posted June 21, 2015 Author Share Posted June 21, 2015 Quoted from Sheepy You say your diff is noisy?What noise, a rumbling? A whine? Could be worth just rebuilding your diff, you are going to strip it for the seals anyway!! 😉Is it a daily driver or just a fun toy? Just use the car for fun Sheepy and the noise is a whine rather than a rumbling. Isnt rebuilding the diff a rather difficult task for a relatively non mechanical person? Or would it be economical to get it rebuilt by a local garage?.. Do you think rebuilding would cost less than getting a refurbed exchange unit from the likes of Rimmers? Quote Link to comment Share on other sites More sharing options...
Encom Posted June 21, 2015 Share Posted June 21, 2015 There is a thread on this in the Herald/Vitesse section.I have used the R160 conversion on my cars as it bolts in without any cutting etc. A batch has just been done (picture below of what you get) of the rear castings and adapter plates, and I understand it looks like there will be a second batch done in the near future as there has been a fair bit of interest. PM if you are keen and I can put you in contact with the guy organising it. Quote Link to comment Share on other sites More sharing options...
Paul Garvey Posted June 21, 2015 Share Posted June 21, 2015 The only problem with the conversion is the diff axle flanges which have become like hen's teeth in these days of CV's and even if you find some they'll need to be spaced out an inch or so either side as the diff is narrower. Also as means welding such a critical component it is likely to come under scrutiny. Speaking from experience I'd keep away from the LSD version as this type will need to be 'backed off' quite a bit by a dff specialist for the less bhp and/or torque and moreso with a Spitfire/Herald than a Vitesse/GT6 - costs a lot. I'd stick with a good std diff. I thnk you can also use the diff head from a Morris Marina as an option but pretty thin on the ground now. Quote Link to comment Share on other sites More sharing options...
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