Lotus Elan

Diff Removal

PostPost by: Donels » Fri Jan 20, 2017 10:43 am

I have just removed the diff from my +2 with some difficulty. It required a pry bar and a mallet to force the diff out resulting in scratched paint, etc. Not a problem as I will paint the chassis before replacement, but "slide out to the left" as stated in the Lotus manual was not possible. The chassis is a Lotus replacement and there is just not enough space to get the diff out. I guess the tolerances on the chassis and diff can result in some builds being too tight. It looks like a clearance could be created by dressing a chamfer on the underside of the diff nose to give 1/8" more space. Has anyone done this?
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PostPost by: Mazzini » Fri Jan 20, 2017 10:53 am

There maybe one or two threads about this issue on the forum...cough :D
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PostPost by: rgh0 » Fri Jan 20, 2017 11:51 am

Different Ford diff noses exist. It helps if you grind the bottom lug off the front of the later ones. A small almost invisible bend in the bottom chassis plate also creates a problem with diff removal, jacking the bottom plate down a couple of mm makes all the difference.

Even after all that the diff still drops on your face as you slide it out to the left per the manual :lol:

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PostPost by: redcarandco » Fri Jan 20, 2017 3:24 pm

Reading this post I do wonder which sort of fool we are all these who race elan and change of diff (ratio )almost for every next race (at least.....very least.... ten times a race season ).....Pfiiiiiiou but I must recognize that doing that since more or less 50 years I just have to snap fingers and diff jump itself in chassis.....re Pfiiiiiiiiou
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PostPost by: Donels » Fri Jan 20, 2017 7:54 pm

I did talk with Brian Buckland on this after the post and he said that the Lotus jigs for making the replacement chassis were hopeless making them very variable with the supplier 'tearing their hair out' until they made their own jig. This would explain why some 'jump' out and others need considerable persuasion. I guess I've got one with small gap!
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PostPost by: redcarandco » Sun Jan 22, 2017 3:13 pm

dear Donels ,in a former post I realize I have been a little bit mocking but I must recognize it is always difficult when you have this heavy thing above your face not coming out easily as it should....and when you try harder to have the whole car beginning to swing on chassis stands.....dreadfull...You know even when it goes easily you will always scratch (+/-)somewhere in cross member...it is almost impossible not to do so....but are you sure to have the correct original diff nose....so many swaps being done by previous owners....I send you fotos of different diff noses the black one comes (for sure) from a genuine+2 the others are exotical almost possible to fit....but anyway keep in mind it is always "uneasy"
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PostPost by: Donels » Sun Jan 22, 2017 5:42 pm

No offence taken and thanks for the pictures. My diff is identical to that in the 2nd photo and back to my original post I intend to chamfer the two ribs on the underside of the diff nose (the shiny bits in your photo) to make it less of an interference fit. I cannot see a problem in doing this nor could Rohan.

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PostPost by: redcarandco » Sun Jan 22, 2017 5:50 pm

Absolutely no problem but be carefull not to go to deep but if you succeed in taking it out( even with difficulties) I think that just cutting the 2 ribs at same level than bottom of curve will be far enough...
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PostPost by: ceejay » Sun Jan 29, 2017 3:52 am

Easy Diff Removal And Replacement

https://www.youtube.com/watch?v=-12F0s58y6k

Lotus elan differential removal and replacement.
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PostPost by: 2cams70 » Sun Jan 29, 2017 5:26 am

Similar to the situation with engine blocks there's actually 3 casting types that I know of that exist for the Ford cast iron carrier housing. The early type fitted to Anglias and Mk1 Cortinas (casting code 105E), the "in between" Type fitted to Mk2 Cortina, Capri's and Mk1 Escorts (casting code 2930E) and the latest type (casting code 73AG) fitted to Mk2 Escorts. As far as I know they are all physically interchageable with due attention to the pinion flange.

The black carrier in your photo looks like a 105E, the grey carrier a 2930E. The different casting are all a slightly different shape. It looks like the 105E one without the "knob" on the carrier nose is the one that fits an Elan best which makes sense sense because the Elan would have been originally designed at the time of the 105E.

The later types had a strengthened differential carrier for the ring gear which I think is still interchangeable with the 105E housing. All the other internal parts - pinion/ring gear, spider gears, bearings, etc. are all the same.

I think the later housing were improved by becoming progressively stronger and with larger oil passages for the pinion bearings. Probably of not much importance in an Elan application.
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PostPost by: ceejay » Sun Jan 29, 2017 7:11 am

Your description of different diff housing types is very interesting. The diff that came with the S2 when I bought it way back in the early 80s was the 3.9. The others, the 3.5 and 4.2, I bought off a local guy who was getting rid of his early Ford stuff. I had no idea as to what they came out of.

The diff flanges I simply machined and modified so that the propshaft would fit on to all of the diffs that I had with out having to stuff around with anything when I decided to change diffs.

The only annoying part with the elan is removing the output shafts and bearings and replacing them back into the Alloy housing each time a diff change over is made.

But I now prefer to run the 3.5, because it gives nice "long legs: out on the free-way, making it easy to cruise the S2 around the 120KPH mark. And the tall ratio is not too bad in the Alps either with an ultra close ratio gear box.
All the elan really needs is one of those nice six speed units on offer in the UK... But where do you stop.
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PostPost by: Donels » Wed Feb 08, 2017 6:25 pm

The diff casing nose has been chamfered and the diff is now a tight, but wriggle-able fit. The ribs on the underside of the casing have been filed as shown in the attached photo's and the alloy housing dressed to be flush with diff casing as shown. Thanks for all those who responded, the YouTube video was particularly helpful.
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img_0022.jpg and
img_0023.jpg and
img_0024.jpg and
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PostPost by: ceejay » Wed Feb 08, 2017 8:24 pm

Donels, that will make a difference when you install or remove the diff, every bit helps. Glad the youtube video was helpful. Maybe you could also take a look at how to fabricate an integral sheet metal diff brace, which is a far better design than what was offered as the original diff brace.
http://elantrikbits.com/lotus-elan-blog/?s=diff+brace
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PostPost by: pharriso » Wed Feb 08, 2017 9:02 pm

ceejay wrote:Donels, that will make a difference when you install or remove the diff, every bit helps. Glad the youtube video was helpful. Maybe you could also take a look at how to fabricate an integral sheet metal diff brace, which is a far better design than what was offered as the original diff brace.
http://elantrikbits.com/lotus-elan-blog/?s=diff+brace


Excellent article, thanks for posting!
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PostPost by: ceejay » Wed Feb 08, 2017 9:06 pm

Thank you, only to happy to help.
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