Lotus Elan

Diff output shaft question

PostPost by: chrishewett » Sun Apr 08, 2007 8:59 am

Having just had another rotoflex failure I have been reading the thread on which cv conversion to go for.
A few years ago I changed my diff which was worn with a good second hand diff. At the time I didn't ask what year car it came from so although my car is 1971 I have no idea what output shafts are in the present diff. Is there any way of checking apart from removing the diff altogether?
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PostPost by: PeterDraper » Sun Apr 08, 2007 11:22 am

Hi I think they are all the same & are also in the baby Elan. The diff as you probaly know is just a Ford unit. I have a pair of shafts for sale.
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PostPost by: schroeder » Sun Apr 08, 2007 11:42 am

Chris

Yes you can remove the inner drive shaft with the diff in place. Obviously a bit more difficult than on a work bench.

The shaft is held in by a circlip that retains the bearing outer race in the housing.

I can't recall from memory if the seal needs to be removed first. I believe that there is a rubber seal that will need to be removed to provide access to the circlip. This seal will be destroyed so get two new ones. bearings should be replaced too while you are in there.

Once you remove the circlip the shaft can be pulled out. Remember this is a lotus so it will not be that straightforward.

The fit between bearing and housing will likely require to be relieved by applying gentle heat to the housing to enable differential thermal expansion to work in your favour. Please remember that the housing is alloy so be gentle.

If it still wont budge loosely assemble the intermediate shaft onto the inner yoke without donuts. This can be used to pull on and as a slide hammer to gently ease the inner shaft out preferably having heated the housing first.

Stu

PS picked up the radiator from the Uk last week. Plan to use it as a pattern to have a couple of aluminum(ium) ones made up. Thanks again.
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PostPost by: garyeanderson » Sun Apr 08, 2007 1:50 pm

Differential seals are installed in the alloy case, the output shaft and the bearing come out as a unit once the large snap ring is removed. Make sure that you clean the area where the snap ring is thoroughly before you pull the snap ring with brakeclean or some other solvent. Once the snap ring is removed, clean again, any junk caught between the bearing and the snap ring groove will break the groove off. The same goes for the upright snap rings of the hub carriers. The seals stay in the case and are not destroyed when pulling but if you apply too much heat that will ruin them. Definitely heat the case, I use a propane torch or heat gun and aim at the outside perimeter of the bearing housing. I heat it until I can still put my fingers on the alloy and not burn them. A couple of light slaps with a slide hammer should do it. If not more heat and be ready to replace the seals. They are cheap compared to the cost of a new case or output shafts.

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PostPost by: chrishewett » Sun Apr 08, 2007 3:04 pm

What I am really trying to establish is whether the shafts are of the later, stronger type. I hope that they are and I won't need to uprate them. Do I have to remove them to establish this or is there any way to tell from the casing the year of manufacture.
Thanks for the replies sofar, at least I will know how to remove them if I have to.
Chris
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PostPost by: garyeanderson » Sun Apr 08, 2007 4:06 pm

Chris

Please post a photo and someone will be able to tell you. 71 should be the later type but being 36 years who really knows what the history of your elan is.

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PostPost by: Matt » Sun Apr 08, 2007 7:09 pm

Hi Chris

The shafts are not hard to remove, a sir clip and a puller made of old bolts did mine.

Below is a picture of an early output shaft Pre- S130
The later shafts are filled in where I have put the red in the picture, so the shaft is the same diameter as the splines the whole way down.

Hope this helps

Matt
Attachments
old-new-output.jpg and
Red shows "meat" on new shafts
1967 Elan S3
1970 Elan S4 Sprint
1972 Europa TC
1973 Elan +2 s130/5
1978 Esprit S1
1981 Esprit S2.2
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PostPost by: john.p.clegg » Sun Apr 08, 2007 10:08 pm

Which you can't see until you remove the shafts-unless you're talking about "failsafe" shafts

John :wink:
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PostPost by: bcmc33 » Mon Apr 09, 2007 12:07 am

Chris,

There would be some form of date stamping on the diff. ? exactly where this would be is another question that maybe someone can answer.
Knowing the provenance of the diff. would be useful, and if it can be proved to be from 1971 onwards, then there would be a high confidence of it having upgraded shafts.

Without removing and stripping the diff. the only reliable method would be a metallurgical analysis. This can be done in situ if you can scrounge a loan of a portable spectrograph machine ? a pretty forlorn hope, I would guess.


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PostPost by: fatboyoz » Mon Apr 09, 2007 3:50 am

Chris,
Which CV conversion did you decide on?
Regards Colin.
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PostPost by: chrishewett » Mon Apr 09, 2007 8:28 am

I have just looked at the diff and the only markings I can see are a large N12 and smaller oc17
Does this give any clue as to the date?
Colin, I expect I will go for the Mick Miller driveshafts.
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PostPost by: bcmc33 » Mon Apr 09, 2007 10:05 am

Chris,
It would seem that if you want to sleep nights you will have to pull a shaft and look.
The information from Matt shows the ideal way to visibly identify the before/after level of shaft. The +2 S130 came out about the same time as the Sprint where it is well recorded that the output shafts were upgraded with tougher steel, so it is reasonable to assume that the same shafts were used for the +2 from that time.
Rohan?s post http://www.lotuselan.net/forums/viewtopic.php?p=63174 shows his input shaft failure for what was a pre-upgraded part. Perhaps Rohan can confirm the physical difference of the before/after shafts as identified by Matt.

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PostPost by: chrishewett » Mon Apr 09, 2007 5:52 pm

Brian,
Bugger! I suppose you are right. Another job I hadn't anticipated. Never mind, here we go.
Chris
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PostPost by: ecamiel » Tue Apr 10, 2007 12:23 am

I have a CV conversion which uses what I am told are unmodified VW output shafts that bolt directly to the CV joints. They are supposed to be much stronger and cheeper than the Lotus bits. Does anyone know about these?
Eric
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PostPost by: rgh0 » Tue Apr 10, 2007 10:59 am

The photo from Matt with the marked up section is how I recall the later shafts. The only external difference is that the fail salfe pins were introduced at around the same time and you should be able to see some remains of the pin in the cetnre of the shaft even if its been cut off if the diff was from a post 1971 car.

I have heard of VW diff shafts being used that bolt straight onto the inner CV but always believed they need machining to get the right spline and bearing mounting surface.

cheers
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