Diff output shaft question

[bcmc33]

Interesting comment from Rohan of safety pins on the diff shafts.

When I did my CVJ conversion there were pins on the outboard shafts only. I did not look too closely at the diff shafts, but there was no obvious evidence of pins having been cut off.

Perhaps the diff is not original, and my smart-ass messages to Chris now applies to me.

Now where did I put that portable spectograph machine???????????


Brian Clarke
(1972 Sprint)

[ianf]

Chris,

I it helps I have had a near Rotoflex failure in the last month. I checked my do-nuts the week before driving to Donington and pulled a segment off one by hand! They had only covered 9,000 miles, the previous ones did 20K. My car does probably 75% of its mileage in France or on holiday and is usually full of luggage with a laden rear end. I think this is not ideal for the Rotoflex couplings. I went for the Mick Miller shafts (it took a deep breath or two as I am generally a believer in original is best) and find the car drives really nicely. My gearbox is getting ready for a rebuild and the vibration between 3-4,000 rpm was very irritating. This has now reduced to a mild buzz with the MM shafts which leads me to believe that my intermediate shafts may have been past their best.

Only downside I have found is that they quickly develop surface rust so I will slap a bit of black paint on when I have a mo.

Cheers,

Ian

[sk178ta]

Following all this, I`ve bought a pair of output shafts, supposedly from a `72 +2. BUT........... compared with Matt`s photo they are still slimmer than the splines at the red line (in Matt`s photo) position. I`m assured they are the later stronger type but are they?
Jim

[rgh0]

Jim

Do they have the donut failure safety pins in the middle or at least signs that they were there once ?

Given Lotus' change control you never know what bits ended up in what car during a change over of specifications.

Rohan

[john.p.clegg]

Jim
The later,stronger type had a parallel shank?

John

[sk178ta]

Rohan,
No they just have a hole in the centre of the doughnut web.
Jim

[rgh0]

If the just have the hole from the the lathe the shafts were turned on then they are pre safety pin shafts and probably probably not out of 1972 plus 2.

However the introduction of the safety pins, the change to stronger steel in the shaft and the change to the shaft profile may all have occured at slightly different times around 1971 and old stock may have been used up for a while so it really a guess what you have.

Rohan

[tdafforn]

Hi Guys,
My +2S130 late '72 didn't have failsafes when I changed ot TT shafts.
It could be that they have been changes, but the rest of the car is very unmolested..
Cheers
tim

[rgh0]

Hi Tim

My 73 plus 2S 130/5 did have the safety pins I had thought they were introduced in 71 or 72 but maybe it was later. Lotus only listed one change to the diff output shafts in the Elan parts manual with the introduction of the Elan Sprint with the part number changing from A026R005 to B026R005. I dont have a Plus 2 parts manual and my Plus 2 workshop manual does not refer to the safety pin style shaft at all, may be the pins and changed shaft profile where introduced after the Elan was discontinued late in the Plus 2 production run in 73? Does anybody have a plus 2 parts manual that lists more than 2 types of diff output shafts?

Anyhow regardless of the above I have never seen a diff output shaft from a 1971 or later Elan Sprint of Plus2 S 130 fail in service whereas I have seen a lot fail in earlier cars.

cheers
Rohan

[JJDraper]

You guys have now got me paranoid! For peace of mind, what are likely consequences of a failure? Where does the shaft break? Looking at the modification (parrallel shank) I guess it must fail there, if so I guess it must be a 'simple' loss of drive, but no collateral damage..... or am I being optimistic!! If it is a matter of loss of drive and a diff rebuild, I will stop worrying and get on with driving.

For the record, I haven't a clue what shafts are in the diff.. My +2 is like the 200 year old broom - only 6 new handles and 6 new heads...

Jeremy

[bcmc33]

Jeremy,

Since my post on this thread a couple of weeks back, I have taken the attitude that if my Sprint does not have the uprated shafts and they fail because of the power from the uprated engine, then it will result in a simple loss of drive.
I have now made sure that the breakdown assistance supplied by my insurance company covers this sort of failure, and that their number is in my mobile phone.


Brian Clarke
(1972 Sprint)

[rgh0]

Jeremy
When the shafts fail they usually do so at the splines or at the diameter change just inboard of the bearing. I posted some photos in another thread of these failures.

No major damage results as its usually a clean break, just loss of drive and the need to get a tow home. The broken bits an usually be extracted with the diff still in situ and replaced.

Rohan

[JJDraper]

Many thanks, another thing to stop worrying about...

Jeremy

[chrishewett]

I agree that you can spend to much time worrying and not enough driving. However as I am going to fit Mick Miller driveshafts I might as well sort this potential problem while I am doing it. I have just looked at my +2 service parts list. The early shafts are listed under +2, +2 Fed, +2S and +2S Fed. Only the S130 has the later part number listed. This is irelevant to me even though my car is a S130 as I don't know what car the present diff came from. I am certain that they don't have pins on them so I assume they are the weaker type. ( I am pretty sure that the original diff didn't have them either). I just wish I had known about this before I sourced a replacement diff.
I have full RAC cover but I would rather not use it when I am in the south of France!
Chris

[rgh0]

Chris

Thanks for the info from the plus 2 parts manual.

It sounds like Lotus introduced the shafts with stronger steel in 1971 when the Sprints and Plus 2S 130 where introduced and changed the part number at that time. The later changes to the Plus 2 with the safety pins and the change in shaft profile came sometime later, maybe in 1973 on the last of the Plus 2 after the Elan Sprint had been discontinued and appears not to have had a part number change.

A shaft that came out of a post 71 car ( i.e. Sprint or Plus 2S 130) should be OK as its the stronger material and I have never seen these fail. The problem is you cant positively identify these shafts as the only change was the material and there is nothing visual until the profile and pins changed later.

If your current shafts have no visual deformation and you are only using them for normal road usage and not doing drop clutch starts in competition then your probably going to be Ok in the South of France.

cheers
Rohan