Lotus Elan

Diff output shafts

PostPost by: garyeanderson » Tue Jul 06, 2010 1:03 pm

bcmc33 wrote:
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?

Hi Brian

The S4 Elan was 45/8221 that I owned, probably built in the July to September 1968 time frame. I had rebuilt it and installed a 1700 cc Twin Cam with Stomberg head, but the cams were pretty mild so I would guess it was an honest 115 to 120 hp, torque would be about the same, maybe 125 lb/ft. I had driven it mostly with the binary throttle and it did have good compression braking. This is the nicest driving Elan combo I have driven and put 45,000 miles on it in 8 years. Anyway on that particular day I was not being brutal on it, I was going past a friends house and saw his car in the driveway so I turned around at the next intersection and stopped to let the traffic clear. I was only heading back a 150 yards so there was no need to be binary about it. It just snapped, the damage had already been done to the output shaft, I was lucky I wasn't moving, as there was no other damage than to the shaft itself. Yes the spline?s have the slightest of twist in the photo. Anyhow the point I trying to make is that you don't know the condition of the diff output shafts unless you pull them out and magnaflux. Once they are out, if you are spending the money to buy the conversion and it?s 800 to a 1000 UK pounds or 1200 to 1500 dollars, than the extra couple of hundred for the output shafts seems like a smart way to go. The fact that most people know very little of the history of the cars they own it would be a shame if they were to break after doing the conversion. That?s just the way I see things I guess, 40 years old any you don't know the history. Just insurance to me not to be left on the side of the road at the worst possible time, as it always is you know.
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PostPost by: frearther » Tue Jul 06, 2010 1:42 pm

When I decided to change to a CV rear end, I checked all the original pieces on my '65/'66 (built/registered) S2. One of the output shafts was severely twisted, the other less so. I had successfully autocrossed the car for about eight years in the 1980's; the PO had also autocrossed. This, of course, meant many quick starts. I knew that this treatment would be hard on the doughnuts, and I inspected them regularly. But the twisted output shafts were a surprise. I'm very glad that I found the problem before completing the rebuild. Knowing this I'd simply replace any old output shafts as a normal rebuild process.
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PostPost by: ftsoft » Wed Jul 07, 2010 12:11 am

Talk about doom and gloom. You guys are scaring me now. I wonder if I should just replace the shafts when i pull out the diff?

Frank
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PostPost by: JJDraper » Wed Jul 07, 2010 7:11 am

On my recent +2 rebuild, I replaced the early output shafts with later ones. The later ones are easy to distinguish from the earlier ones as per the attached picture (from ebay some time ago). The later ones have no shoulder after the splines. The older ones I took out were a little worn, but not twisted. I guess the quality control was patchy, but as has been said, without crack testing who's to say when they would let go.

Less of the doom and gloom, at least when they fail they just strand you until a flat bed arrives. If you are really paranoid carry a spare!

Jeremy
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PostPost by: garyeanderson » Wed Jul 07, 2010 10:32 am

JJDraper wrote:I guess the quality control was patchy, but as has been said, without crack testing who's to say when they would let go.

Less of the doom and gloom, at least when they fail they just strand you until a flat bed arrives. If you are really paranoid carry a spare!

Jeremy


Jeremy

If they Diff output shaft fail at a stop sign or other situation where you are stopped then you are correct in that its an inconvenience. If they fail at speed, like on a downshift from 4th to 3rd, they will flail and make a real mess out of the rear of the chassis, fiberglass, and maybe more. I was lucky that mine broke at a stop sign 3 miles from home.

Gary
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PostPost by: rgh0 » Wed Jul 07, 2010 11:03 am

Almost always the shaft or the donut breaks at low speed in high torque situations such as starting from stationary. This can still cause a fair amount of damage if its the donut that fails. The diff output shaft always fails inside the diff and the diff bearing continues to support the section of the shaft outside the diff so nothing flails around to cause damage.

cheers
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PostPost by: garyeanderson » Wed Jul 07, 2010 1:05 pm

rgh0 wrote:Almost always the shaft or the donut breaks at low speed in high torque situations such as starting from stationary. This can still cause a fair amount of damage if its the donut that fails. The diff output shaft always fails inside the diff and the diff bearing continues to support the section of the shaft outside the diff so nothing flails around to cause damage.

cheers
Rohan


Yes Rohan you and Jeremy are correct, not thinking well without the first cup of coffee this morning. My mistake for not thinking this through. I guess what I am getting at is 50 to 60 percent of all Elan's (not plus2's as I don't know that info) are equipped with these early, possibly failure prone shafts. That includes all S1?s. S2?s and S3?s and a bit of the S4?s production as well. After 40 years they may be considered as potential failure waiting to happen.

Now the original question was which CV to buy, one with or one without the output shafts if you were to replace the donuts with CV's. So knowing what I know and remembering the pain I put myself through I would replace output shafts if I had the money to upgrade to CV's. I would replace the output shafts just because the price difference is not a lot of money in relation to the total expense of the conversion and the amount of work to get the complete job done just once. But that?s just me, I like to do the job just once and not work on it again if it isn't necessary. Anyway it your money spend it how you think it should be spent.

Gary
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PostPost by: frearther » Wed Jul 07, 2010 1:20 pm

ftsoft wrote:Talk about doom and gloom. You guys are scaring me now. I wonder if I should just replace the shafts when i pull out the diff?

Frank

Yup!
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PostPost by: CBUEB1771 » Wed Jul 07, 2010 1:56 pm

garyeanderson wrote:blood running in my hair


I was wondering why you got rid of your hair. I color mine gray to look more mature.
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PostPost by: frearther » Tue Jul 13, 2010 12:04 pm

garyeanderson wrote: I color mine gray to look more mature.


I've become fond of white - it's neutral and goes with all my outfits :|
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PostPost by: Pistacchio sprint 72 » Wed Sep 19, 2012 12:34 pm

It is a bit hard to make an opinion. the subject of a broken outputshaft is scary.

But the outputshaft broken we are talking here are form the early batch. right?

Do we know sany of the later stronger output shaft who failed?

My Sprint is from 1972. It had the Miller CV joint driveshaft conversion done in 07 by previous owner. Do I need to take the car to a mechanician and change these outputshafts by TTR ones?

the labour cost scares me...
or is that outpushaft conversion is not necessary on the later sprints?

Thanks
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PostPost by: Elanman99 » Wed Sep 19, 2012 1:31 pm

In about 1972 I replaced the three diff oil seals because one of them was leaking. I noticed that the output shafts splines had a 'twist' and thought I should swap sides when I re-used them (it never occurred to me to fit new ones). In the event I put them back in the same positions.

They have been there ever since (in the region of 180,000 miles) and although I don't thrash the car much now they certainly had a hard life in the first few years.

I think that if I had reversed them they would have broken sooner or later. I don't know if the following has any truth in it but, my current thinking is that the torque profile needed to break them now, is very slightly greater than it would be for the same (but unbent) shaft.

I hope to fit a 3.55 diff shortly so will soon get to see what they look like again.

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PostPost by: Davidb » Tue Jun 20, 2017 7:45 pm

I am resurrecting this thread because: 1/ I want to hear if there are any stories of the later shafts breaking and b/ I have my shafts out right now because they were seeping oil and I don't think they should.

The local Elan expert tells me that the early shafts have no taper and the later ones do-the opposite of what is said in this thread!

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PostPost by: rgh0 » Wed Jun 21, 2017 9:54 am

Davidb wrote:I am resurrecting this thread because: 1/ I want to hear if there are any stories of the later shafts breaking and b/ I have my shafts out right now because they were seeping oil and I don't think they should.

The local Elan expert tells me that the early shafts have no taper and the later ones do-the opposite of what is said in this thread!

Dazed and confused in Vancouver...


Sounds like your local Elan expert is also dazed and confused.
I have never seen or heard of a later stock output shaft break.
The diff output shaft seals rarely leak if assembled correctly even after many , many years so if leaking you should replace like your doing

cheers
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PostPost by: Davidb » Wed Jun 21, 2017 4:42 pm

Thanks for the response Rohan. I have a pair of later shafts now and will fit them. I am wondering if there is a problem with the breather in the diff to cause the leaks.
Since I installed a 3.55 cwp I wont be doing any racing starts so the shafts should last!
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