Diff output shaft question

[chrishewett]

I just spoke to Ann Miller about her cv conversion driveshafts. She tells me that the reason Mick decided to supply these is that they had so many customers reporting rotoflex failures due to poor quality, even when they were new. Mick decided that they could not supply a part that was so unreliable.
She seemed to think that the diff output shafts were uprated very early and only S1 and S2 elans have the suspect parts. She also said that after selling 360 sets of cv conversions she hasn't had anyone come back to her saying that they have had a output shaft failure which they suspect was due to fitting the new driveshafts, although she has had customers report failures when they were running rotoflexes.
Bearing all this in mind, Ann Millers high standing and Rohans input, I have decided to order a set of Mick Miller driveshafts tomorrow and ignore the diff output shaft question.
I will report back when I have fitted them.
Chris

[chrishewett]

A late addition to this thread.
I have just got back from a trip to silverstone, unfortunately not under my own steam. A diff output shaft failed as I was storming out of a roundabout. This is something I was half expecting as I had arrived at the conclusion that my output shafts were not of the uprated kind. I must admit that I had been seeking the full potential from the car for the last hundred miles before it failed.
I am still very impressed with the driveshafts but I would recommend anyone fitting them to investigate uprated output shafts. I think that if I had driven in a less aggresive manner they would maybe have lasted forever but they appear to be a weak link and safest to upgrade them.
Next weeks job!
Chris

[rgh0]

Chris

Can you post a photo of the failed shaft once you get it out. Always interesting to see where and how it broke. A close up of the fracture surface will show whether it was a fatigue failure from a crack that had been slowly growing from before you put the Cv's in the car (which is the normal cause of failure in the early shafts).

cheers
Rohan

[chrishewett]

Rohan,
I will certainly do that. If I can't get it into the garage this week I am away for the following week and so it will be the week after that. As soon as I have it out I will post photos.
Any suggestions where to get the uprated shafts from? Are Tony Thompson shafts different from standard lotus uprated shafts? Would the lotus ones be good enough? They arn't cheap whatever.
Chris

[rgh0]

Chris
I presume any genuine Lotus shafts available as new would be of the later type (good steel, big dia shank, and maybe with the centre fail safe pins?) and probably OK. As I have observed before I never seen any of these later shafts fail and they have certainly been OK on my 73 plus2.

However sometimes hard to tell theses days if getting a genuine Lotus part or a cheap copy especially wih something like a drive shaft were you are reliant on proper steel being used.

If cost difference is small or any concerns over the authenticity of the "genuine" Lotus item I would probably go for the TTR shafts as greater certainty that you are actually getting a strong enough item.

The shafts I use were local one off manufacture many years ago, The Elan Factory can also supply uprated shafts but cost delivered to UK would be similar to the TTR shafts probably, but worth a check on price and if they have them in stock

cheers
Rohan