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Late GT6 Mk 3 - Non-Rotoflex - Wrong rear spring?


Kevin Atkins

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Good evening all,

My recently acquired project car is coming along.. it's been off the road for 10+ years and has so far taken a fair bit of recommissioning. This weekend I thought it was about time I tackled the rear end.

The back of the car is sitting too low and the wheels have a rather pronounced negative camber on them, and last weekend she developed a bit of a nasty vibration from the back so I thought I'd sort the prop and driveshaft UJs etc.

Driveshafts are now removed and looking at the rear spring, it doesn't look like it's the late Mk 3 swing spring arrangement at all. It looks to me like a Mk 1 - there is no central pivot and the spring is clamped to the top of the diff. I'm just wondering what could have happened here? It looks like Rimmers do a swing spring conversion kit - are they any good, and I'm not sure about driveshafts, I believe there are different lengths? It's puzzling why it should have the wrong spring in it, but guess a 50-year-old car will have a few skeletons in the cupboard!

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Late Mk3 swing spring should certainly have the pivot, but genuine MK3 springs are very hard to find. There is a difference in the Spitfire swing spring, and the GT6 version, but many suppliers continue to sell the same spring for both cars.

GT6 had six leaves, but the Spitfire had five thicker leaves, and the large end 'eyes' also differ and may foul the brakes. Make sure if you're buying one you go for the proper spring.

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Thanks @Pete Lewis and @Colin Lindsay - I've just measured the driveshafts (rather approximately but good enough I think), showing ~ 20.5" from centre of UJ to end of shaft, so my understanding is these are long shafts.. Thanks for the heads-up on needing to blank two holes - it does indeed have 6 studs - and getting the correct spring. I'd like to return it to swing-spring if possible as I'm not happy with the current arrangement..

On a slightly different tack, while I've got the back end apart (and hijacking my own thread 😉 ) - I added oil to the differential a week or two back and it's possible I've overfilled it - having jacked the car up to dismantle, oil is now dripping out of the front of the diff - it looks like it's coming from the pinion, so wondering if the front oil seal has blown? Or it could just have been bad anyway after a decade or more sitting idle and then being pressed into service again.. question though - apart from blowing oil seals, would overfilling have caused any other ill effects on the diff? I did take care the car was level when filling but I could have fouled up..

Thanks for the help!

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The front seal will leak if the car is tilted forward, or if overfilled, but thankfully on the few I've refurbished with new seals I've found that it stops after some time (and yes there is still oil in it). Excess oil will run out, no harm caused, you can't put massive amounts in anyway due to the way it's filled. On top of the diff, on one of the rear mounts, there's a split pin in a hole that allows pressure to escape - if you can reach it, wiggle it about to make sure it's free and not blocked, but this will prevent any excess pressure forcing oil out past the seals until the level settles. (Excuse the photo, it's the only one I have to hand showing the split pin location)

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13 hours ago, Kevin Atkins said:

On a slightly different tack, while I've got the back end apart (and hijacking my own thread 😉 ) - I added oil to the differential a week or two back and it's possible I've overfilled it

How much oil did you have to put in the diff before it started to run back out of the fill hole?

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sound like you need a pinion oil seal replacement 

you can do this on the car remove coupling and carefully dig the old seal out 

without knowing the history of the diff it may have acollapsible spacer to sort the bearing pre loads   so mark the nut and return it to the same

position as before removal of you can over tighten and increase the pre load on the brgs.

a solid spaer between the brgs  is just do it up to the torque in the book 

withe the seal out you can remove the outer brg. and see waht spacer you have  

solid with shims     or tube with raised  deformable ring in its middle 

Pete

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Thanks guys - that's very reassuring re. possible overfill. I probably put approximately 300 - 400 ml in, so quite a lot.. There was / is a fair bit of old oil (dried on / mixed with road dirt etc, not shiny and recent) on the outside of the diff casing, so I figured if it had come out I'd really need to get some fresh in there, and it's certainly quieter now. I'm just weighing up my relatively clumsy spanner skills against fitting a new pinion seal vs. leaving well alone in case I muck it up - I'm going to assume it's not the original diff with it being a six-hole on top, so maybe it's from an early car, or maybe not even a GT6? Murky history - a mate at the pub asked me last night 'how many owners has it had?' and when I replied 'something like 15' he was a little shocked. But that is 15 over 50 years.. ok, it's still a lot 😜

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use EP140  makes a good noise reduction and takes longer   to leak out   

quite a few of us have gone to a 140 in the diff   never i use in the gearbox  the baulk rings would really struggle to Sync. 

age of diff  being a 6 hole its a good chance you have a solid spacer  which makes the job less guesswork 

Pete

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Thanks - yeah, looks like it'll need doing then.. Good call on the EP140 Pete - given that it was very low on oil before, whilst topping up has cut the racket considerably, it's still a bit noisy so anything to help there will be great. It's probably suffered some accelerated wear with the low oil level but it'll have to do for now, plenty of other issues to sort first! Hopefully I'll be able to enjoy the car over summer..

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So back on the car again, I've got diff pinion oil seal to fit, and a swing spring - looks like it's a five-leaf job from Rimmers but I'll give it a try.. one thing that I am struggling with is removing the old centre stud from the diff so the peg on the new spring can engage in the hole... I've wound two nuts on the old stud, tried heat, penetrating oil, but it doesn't seem to want to shift. Am I missing something or is it just a case of keep trying?

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20 minutes ago, Kevin Atkins said:

So back on the car again, I've got diff pinion oil seal to fit, and a swing spring - looks like it's a five-leaf job from Rimmers but I'll give it a try.. one thing that I am struggling with is removing the old centre stud from the diff so the peg on the new spring can engage in the hole... I've wound two nuts on the old stud, tried heat, penetrating oil, but it doesn't seem to want to shift. Am I missing something or is it just a case of keep trying?

what centre stud is this? I thought it was just a blind hole that the spring locating peg went into.....

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Thanks for the heads-up on the stud extractor Pete, I have duly ordered one. For now, I have put the car back together again with the old spring as I need it mobile again as soon as possible and didn't want to bodge or risk snapping the old stud off etc. It's been a bit of a marathon so far - new drive shaft UJ's, brakes at the back end; then on the engine front.. I was running into endless trouble with a pair of SU HS6's that had been fitted, fuel leaks, rough running etc. Decided in the end to fit a new fuel tank and a pair of refurbished CD150's so it's back to stock, and looks very nice. No idea yet if it runs OK as the water pump return pipe decided to disintegrate this afternoon so got to get one ordered tomorrow.. let's just say there were a few choice words when that happened at the end of a tiring weekend on the spanners...

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there are a good few cars i have returned from HS6 to CD|S and they do run far better with a triumph spec  carburation 

 

get a stainless pipe  last for ever the old are renowned for giving up when you need to twiddle it 

while its off check the short pump adaptor is clear 

the banjo bolt in the manifold is another nightmare will eiter unscrew easy or end in disaster as the bolt fractures 

pete

 

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Thanks Pete - yeah luckily the banjo bolt was fine although I did buy another one pre-emptively, so the manifold and carbs are all ready to go.. As regards the pipe - yes got a new stainless pipe + collar nut and olive on order, I've also ordered a new adapter just in case - do they come off from the ally pump housing OK or is that likely to be troublesome? Also, I couldn't see any mention of a sealing ring or anything for the adapter, not sure if anything is needed there too?

Ian - yes it's a remanufactured tank from Rimmers; quality and fit were good, it went in without trouble. The box it came in said 'Made in Taiwan', how depressing that we can't even manage to manufacture something like that any more... Still, it seems decent. The old tank that came out was in good physical condition, would just need a good detergent flush to get rid of old fuel laquer, so would be free to anyone in need. It's too good to scrap, I just haven't got the time / facilities to sort it..

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the adaptor will be fine , just unscrew it,   ordering a replacement is not needed but will make a spare as the mix of cast steel /alloy /steel adaptor and pipes the hole in the adaptor 

often needs a drilling out as it attracts crud  

cant remember if its a taper thread into the pump body but a smear of sealer will work fine , not aware of any sealing washer .

make sure as with any olive  that the pipe protrudes well beyond the olive 

Pete

 

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On 20/02/2023 at 20:08, Pete Lewis said:

what triumph developed does what it says on the label 

i have a avid hate of many must haves they all cause some chaos 

the basics  just work well for most driving  and peace of mind 

Pete

My sentiments entirely - I'd rather trust the original engineers than my own judgement on this sort of thing..

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