Lotus Elan

Overhauling the back end

PostPost by: JonB » Thu Nov 23, 2017 11:36 am

Hi

I'm after advice on a back end overhaul. I think I need the following done, at a minimum:

  • New diff oil seals, maybe bearings
  • New bushes throughout
  • Sue Miller CV drive shafts
  • New gearbox top mounts, maybe the stronger TT ones though they are expensive!
  • Shock absorbers (any suggestions?)

The thing is, I do not want to start this job and find I have forgotten something. As I understand it, some nuts and / or bolts should be replaced when doing this. Is there a list anywhere?

Thanks
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PostPost by: jono » Thu Nov 23, 2017 12:02 pm

Jon,

You could spend a lot of money there. I would first confirm that all of the work you've outlined is actually needed.

The CV shafts are certainly a must have in my view. I fitted the TTR top diff mounts to my car as I understand the originals don't last long. The TTR mounts are as good as new after 13,000 miles.

Shocks (if required) - Koni. I would not advise to use AVO based on personal experience.

Diff - uprated ot later, stronger, output shafts are worthwhile if you don't already have them. to change the diff output seals you will need to fit new output shaft bearings but they are cheap - just get a good make, SKF, FAG or similar. I'd be surprised if you need to change the CW&P bearings - is it noisy?

Bushes are definately worth doing - don't be tempted by poly, go for the original metalastic rubber bushes.

Check the rear wheel bearings - best done when you on with the above. Bit of a faff to get them right but there's lots about it on here. It took me 2 attempts to finally get them right!
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PostPost by: JonB » Thu Nov 23, 2017 1:44 pm

Hi jono

I agree about the rubber bushes, plus they are much cheaper. I won't be doing enough miles to justify the poly bushes. There's no play in the rear wheel bearings that I could feel, so I won't bother doing them. My car is a later Plus 2 - 1973 - so I hope it has the stronger output shafts fitted as it is a 130/5.

I'm not looking to spend a stack here - I anticipate the main expense will be the CV joints and TT mounts. Maybe I could leave the shock absorbers for now, but I am pretty sure they are gone. Need to check the receipt file, see when they were last done, if at all.

Anyway, I guess I will have to call Sue Miller again..

Cheers
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PostPost by: SENC » Thu Nov 23, 2017 2:00 pm

Will be following recommendations and your work closely. I have a 69 S4 that will need similar work (as well as front end bushing replacement) and for which I've started a similar list and also been debating the switch to CVs. Good luck, and lots of pictures, please!
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PostPost by: elancoupe » Thu Nov 23, 2017 3:51 pm

With cv joints, I would recommend limited travel Koni shocks from TTR.
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PostPost by: jono » Thu Nov 23, 2017 5:01 pm

Jon,

The paradox is that my polybushes did not last more than 9k miles! They wore oval on the crush tubes and so I went back to the original bushes so there's no real argument that they provide a better lifespan or for that matter better ride or handling. Found the same with the poly trunnion bushes.

The rear shocks are naturally very soft so don't mistake that for them being knackered. The rebound should be fairly slow with no 'return' when it reaches the top of the stroke, doing a simple bounce test.
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PostPost by: steve.thomas » Thu Nov 23, 2017 6:00 pm

Jon,
I would agree with the earlier comment to avoid AVO dampers. If you are going to dismantle the rear end I would suggest you replace or at least check the strut top mounts (Lotocones). They are bolted to the chassis using thin headed bolts which can be a real PITA to undo - a socket with the bevel ground off is perhaps the best tool.
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PostPost by: Orsom Weels » Thu Nov 23, 2017 10:38 pm

elancoupe wrote:With cv joints, I would recommend limited travel Koni shocks from TTR.


Don't need em on a +2 :) , the extra length of the drive shaft reduces the angles at full drop so CV lock up isn't a problem. 8)
As jono mentioned the rear end can seem a bit soft, as long as it isn't bouncy. However, do check that the aeon rubbers are still on the damper shafts, they play an important role in the rear suspension on an Elan & +2, they're not just bump stops. They act as a sort of secondary spring to stiffen things up when close to full compression preventing severe body roll. If they're missing or shot it will detract from the handling characteristics.

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PostPost by: JonB » Fri Nov 24, 2017 6:53 am

Hi Tim

Are aeon rubbers those big fat gaiter looking things at the top of the shocker shaft? I'll check them. The back end is very very soft indeed and I've done a quick bounce test already. Very slight rebound.

On a run to test the lights last night, I noticed quite a bit of body roll and vagueness in the steering. I can't put my finger on it, but I had to continually correct the car as it steered too much or too little. I can't feel any play in the steering mechanism. I put this down to the shock absorbers. The fronts seem pretty good on the bounce, so all that's left is the rear.

I still have to check the tyre pressures. They are relatively low on the Plus 2: 20psi front, 24psi rear according to the owner's handbook. The car has recently fitted Kumho tyres all round.

Cheers
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PostPost by: Orsom Weels » Fri Nov 24, 2017 8:25 am

Hi Jon,
Yes, you're on the right track re the aeon rubbers. If they need replacement, originals are no longer available, but there is a VW part that is a good substitute, there's a thread on here somewhere with the details etc, but typically I can't find it at the moment.
Is what you're experiencing bump steer ? If the steering rack height isn't set correctly with shims, or the rack mountings are damaged, this can make them bump steer quite badly. Again, there's loads of threads on here dealing with that. Try a search, but I hope you have better luck with the search facility than I do :(
I have Kumho tyres on my +2 & reckon they're as good as anything else I've tried on it, better than most ! I run the pressures a little higher though at 22-24 psi front & 24-26 rear. A well set up +2 with std suspension all round should handle superbly whilst still giving a nice compliant ride, there shouldn't be too much body roll. Again, there's lots of threads concerning +2 suspension & what to do to improve it. Very little is the simple answer for general road use, Colin & his minions got it right first time :) If you need to renew any of it, keep it as close to original spec as poss & you won't be far wrong. Sounds like a geometry check might be worthwhile, your tracking could be out a little, that can cause many of the symptoms you describe in the steering.

Regards, Tim
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PostPost by: JonB » Fri Nov 24, 2017 8:41 am

Tim, I think there's no bump steer - happened whether or not there were bumps. Might be me not being used to the car, it has very odd heavy steering and a tiny thin steering rim (14" early Elan). Feels very wallowy in the bends, yet grips the road tenaciously on fast roundabouts albeit with too much body roll IMHO.

The problem is that I have nothing to compare it to until the next Club meeting (in three weeks). I'll just have to be patient.

At least the lights are sorted, so I can drive in the dark without fear of blackouts.
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PostPost by: Orsom Weels » Fri Nov 24, 2017 9:07 am

JonB wrote:it has very odd heavy steering and a tiny thin steering rim (14" early Elan).


Shouldn't feel heavy, it should be nice & light, perhaps not as light as some of the modern assisted systems, but certainly not heavy. I have a 13" steering wheel with a little fatter rim in mine to give me a bit more knee room & can steer easily with one hand in all but the tightest turns.

JonB wrote:The problem is that I have nothing to compare it to until the next Club meeting (in three weeks). I'll just have to be patient.


Yes, it's always good to have a bench mark, one of the reasons I recommended you try as many cars as possible while you were looking. If we were a bit closer, you'd be welcome to come & try mine, but it would be a long old trek just for a test drive :lol:

JonB wrote:At least the lights are sorted, so I can drive in the dark without fear of blackouts.


Great stuff :D You'll get there in the end :wink:

Regards, Tim
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PostPost by: Donels » Fri Nov 24, 2017 9:59 am

If you have odd, heavy steering it could be the front trunnions are dry or have been lubricated with grease that has gone solid. This can quickly lead to the upright thread shearing. I would check before driving again.

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PostPost by: vincereynard » Fri Nov 24, 2017 10:46 am

Above walking pace the steering should not be heavy.

Jack both front wheels up and spin it lock to lock. Check for stiction. It could simply be a semi- seized
ball joint / trunnion. (As Dave suggests above.)

Get it 4 wheel alignment checked. The rears could be way out - that can make it twitchy in a straight line.

Personally I think you need some compliance in the drive train. Its all decades old and even a new Beemer has a form of DoNut on the propshaft. (Or did!) Spyder do a single rotoflex (failsafe) with a single CV.
Something to take the shock other than an ancient output shaft!

Toad has them fitted and I have not noticed any suggestion of wind up.
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PostPost by: JonB » Fri Nov 24, 2017 11:01 am

Also could be tyre pressure, which I'll be checking today.

I knew about the trunnions, having done much research a few months ago when I was looking for a Spitfire. I actually saw two of them at rather unrealistic prices considering the condition, and decided not to buy. I have long experience with Spitties, having owned four of them in the past (although I never serviced the trunnions myself, or knew that they were supposed to be lubricated with EP90).

The rear suspension isn't really adjustable, is it? So how can it be out of alignment (other than by means of worn bushes)?
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