Lotus Elan

Diff output shafts

PostPost by: saildrive2001 » Sat Jul 03, 2010 8:16 pm

Before I make the final decision whether to replace the donuts with a C/V system I would like to know how many people have had problems with the diff output shafts? Both TTR & RD sell their respective conversions with new output shafts. I know from past posts that they are one of the weak spots on the car but how much of a problem is it really? How many people have had them break in normal road use?
Any feedback would be appreciated.
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PostPost by: rgh0 » Sun Jul 04, 2010 1:14 am

Depends what you mean by "normal road use" a little. The early style shafts ( pre 1970 approx) would break if the cars performance and acceleration potential was used enthusiastically. The failure was quicker if used on the track or hill climbs for drop the clutch starts with sticky tyres but can eventually occur in normal road use cars if you give it the same sort of treatment regularly as many owners do.

If you have gone this long as the original owner and are still using donuts and dont change the donuts once a year then your normal road use driving style probably does not stress the diff output shafts to much and it is probably not mandatory to change them when fitting CV's or a uni joint / sliding spling style shaft. However removal and an inspection for twisted splines and a die penetrant crack test for cracks when fitting the new drive shafts would be worthwhile if you buy one of the kits that does not offer the relpacement diff output shaft as part of the kit.

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PostPost by: saildrive2001 » Sun Jul 04, 2010 3:38 pm

Thanks for the reply & suggestions Rohan. The car has not been driven for the last 30 years hence the complete rebuild I am going through. When I say normal road use I would say that I used to drive the car to it's safe performance on the road but I never did any drop the clutch starts. I would ensure that the clutch was fully engaged before applying throttle.
What I really want is any feed back from all those that have changed to c/vs. Have they had any problems with the standard output shafts.
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PostPost by: bcmc33 » Sun Jul 04, 2010 6:05 pm

There is a history of twisted spline failures with the original steel spec'ed output shafts and that's why Lotus changed the steel spec (IIRC) from 25 tonne to 40 tonne steel for the output shafts and wheel spindles. The timing of this introduction is not known to me, but I guess it would have been for S4 as the Sprints definitely had them to suit the increase in engine torque/power. They can be identified by the addition of a 'safety peg' welded in the centre of the spider legs.
However, having said this, I doubt that an S4 Elan on donuts and being driven with some reasonable caution from standstill would cause the output shafts or wheel spindles any problem.

Modification to solid driveshafts would probably change this opinion.

Rohan's advice to inspect the splines is very good advice as you have no idea what treatment the car had from previous owners.
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PostPost by: ftsoft » Sun Jul 04, 2010 6:10 pm

Well... I've read the posts about them breaking, but I have a different story. I guess YMMV. My 66 Elan has been raced in SCCA Cp, autocrossed and driven close to 80,000 miles besides. Most of that was before 1975 and the car is now back on the road and doing quite well with no doughnut issues or shaft issues.

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PostPost by: bcmc33 » Sun Jul 04, 2010 6:25 pm

ftsoft wrote:Well... I've read the posts about them breaking, but I have a different story. I guess YMMV. My 66 Elan has been raced in SCCA Cp, autocrossed and driven close to 80,000 miles besides. Most of that was before 1975 and the car is now back on the road and doing quite well with no doughnut issues or shaft issues.

Frank

That's what I like to hear - a heart warming satisfied customer story. :)

It certainly puts us pesimistic doom laiden people in our place. :roll:
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PostPost by: pauljones » Mon Jul 05, 2010 10:17 am

Ive had Quaife/TTR output shafts on mine,paid for by a PO.So I cant comment on the before,but I drove mine quite hard for a while and had no problems.To be honest,I didnt have any problems with the origonal drive shafts either but I just orderd some Sue Miller shafts for peice of mind.
I think it comes down to your style of driving,and the cost.

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PostPost by: ecamiel » Mon Jul 05, 2010 12:32 pm

Output shafts do fail and it's expensive, tearing up fiberglass, fuel tank, etc. It's not worth the chance. While you're at it, crack check or replace the outer axels as well.
It's not just expensive, it's your life.
I have 2 sets of twisted ones from a street driven car with doughnuts.
If a car has been race prepped it almost certainly got up rated shafts at some time in it's life.

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PostPost by: ftsoft » Mon Jul 05, 2010 5:43 pm

bcmc33 wrote:
ftsoft wrote:Well... I've read the posts about them breaking, but I have a different story. I guess YMMV. My 66 Elan has been raced in SCCA Cp, autocrossed and driven close to 80,000 miles besides. Most of that was before 1975 and the car is now back on the road and doing quite well with no doughnut issues or shaft issues.

Frank

That's what I like to hear - a heart warming satisfied customer story. :)

It certainly puts us pesimistic doom laiden people in our place. :roll:


Not really trying to put anyone in their place. Just my experience. As for doom, I'm still extremely nervous taking the car out since it's rebuild. I inspected the doughnuts pretty carefully. I'll get a chance to look at the shafts perhaps, because my diff is leaking and I probably should get into it.

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PostPost by: bcmc33 » Mon Jul 05, 2010 5:47 pm

I guess I should have explained what I've done with my car.

I put TTR 100 tonne billet steel shafts and spindles in my car when I changed to solid driveshafts. But this was in advance of increasing the engine power and torque to make it a reasonably competative (occasional) sprint and hill climb car.
I'm afraid my right foot does not understand "normal" driving when I'm behind the wheel of the Elan - strange really, as it is very normal when driving my everyday road car or the wife's shopping trolley.
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PostPost by: Allison » Mon Jul 05, 2010 8:31 pm

Keith,

we don't do normal road use but we get by quite happily with donuts and what were normal diff shafts until we snapped one (for the very first time) in Morocco. At the time we were bump starting it in reverse in the dusty main street. We got it welded in town and carried on reasonably - including trying to drive down a river bed. Go to rallyelan.com and look under casablanca 2009.
We now have a Sue Miller replacement one side and original the other and it never occurred to me to have a problem with them. We've recently got back from 5 weeks and 6250 miles in Argentina and Chile and diff shafts were not on the radar. I'd stay with donuts and ordinary shafts

Peter
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PostPost by: garyeanderson » Mon Jul 05, 2010 11:38 pm

At a stop sign, let the clutch out on my old S4 and I had a box full of nothing, shift though the gears without the clutch disengaged as fast a I could and didn't move an inch. When I got it home I was a bit upset so I jacked up the Elan and started to disassemble it. Undoing the first donut, the 1/2-inch drive ratchet slipped off the nut. I was pulling pretty hard and hit myself in the forehead, I was bleeding a bit and still pissed so I was going to finish the job, blood running in my hair. While still undoing the same nut the stupid ratchet slipped again and this time I was not only bleeding bad but also now balling my eyes out. I finally finished the job that night and went to bed only after extracting the broken stub, I keep it on the window sill in front of the kitchen sink to remind myself to spend the money where you need to and not be so stupid. I have CV's now with the upgraded diff output shafts. Tell me it?s worth saving a couple hundred and I'll give you the same ratchet so you can have the same enjoyment I did

Gary
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PostPost by: rgh0 » Tue Jul 06, 2010 3:35 am

Hi Gary

I have a similar putput shaft to remind me they fail. I also have another one with twisted splines that was about to fail before I replaced it. Any Elan with the earlier shafts will suffer a failure in this area eventually. I dont believe it is donuts versus Cv's that makes the difference but how the car is used. Drive gently and they will last a long time ( 30 plus years), drive more enthusiastically and they will fail quicker (10 to 20 years), race it and they will fail even quicker (1 to 2 years).

I am amazed a race car as reported above lasted any signficant period with the standard shafts but then you can always be lucky and have the orginal shafts that just happened to be made from a batch of better than normal steel I guess and the style and amount of race driving will also affect the life. My experience is that you go from a good standard shaft with no cracks or distortion (but unknown fatgue life used up) to failure in a year or 2 when using on the track for 5 to 10 weekends a year with 4 or 5 drop clutch starts each weekend plus lots of aggressive gear changes up and down also putting strong shock loads into the shafts

The stronger shaft design was definitely in use for the Sprints and plus2S 130 from 1971 on that also had the safety retaining pin arrangement , given the Lotus control of change exactly when they were introduced is not clear but I have seen and heard comments about them being in late S4 cars and plus 2s made in 1970.

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PostPost by: Galwaylotus » Tue Jul 06, 2010 7:32 am

garyeanderson wrote:. . . the stupid ratchet slipped again

I guess you had better get a smart ratchet!!! :lol:
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PostPost by: bcmc33 » Tue Jul 06, 2010 9:14 am

garyeanderson wrote:At a stop sign, let the clutch out on my old S4 and I had a box full of nothing, shift though the gears without the clutch disengaged as fast a I could and didn't move an inch. When I got it home I was a bit upset so I jacked up the Elan and started to disassemble it. Undoing the first donut, the 1/2-inch drive ratchet slipped off the nut. I was pulling pretty hard and hit myself in the forehead, I was bleeding a bit and still pissed so I was going to finish the job, blood running in my hair. While still undoing the same nut the stupid ratchet slipped again and this time I was not only bleeding bad but also now balling my eyes out. I finally finished the job that night and went to bed only after extracting the broken stub, I keep it on the window sill in front of the kitchen sink to remind myself to spend the money where you need to and not be so stupid. I have CV's now with the upgraded diff output shafts. Tell me it?s worth saving a couple hundred and I'll give you the same ratchet so you can have the same enjoyment I did

Gary,


The pictures show the original 25 tonne steel shafts, so whatever the build date of your car, it was before the Lotus upgrade.
Is it my imagination, or are the splines slightly twisted, also?
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