Lotus Elan

differentiial gasket

PostPost by: seniorchristo » Fri Jan 18, 2019 2:06 pm

I'm rebuilding a spare 3.77 diff and purchased parts from Paul Matty. The only gasket available was the "thick" gasket so I purchased it. It is approximately .030" thick. The manual talks about a dowel type differential and mentions the gasket should initially be .009"-.011". What is the correct procedure for determining the thickness of gasket required?
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PostPost by: Donels » Sun Jan 20, 2019 5:58 pm

Just had my diff rebuilt by PJS Sportscars. Paul told me they used a 'thick' gasket. Apparently it’s more to do with keeping it oil tight.
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PostPost by: patrics » Sun Jan 20, 2019 9:03 pm

Hi,
Just my opinion but surely the gasket has to be the correct thickness for the output shafts to align correctly.

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PostPost by: Bud English » Sun Jan 20, 2019 10:22 pm

The gasket thickness is a lot less of a miss alignment for the output shafts than the suspension traveling up and down. The gasket thickness only moves the third member, with the output shafts, forward by the thickness difference between gaskets. I'll bet the rubber mounts for the diff allow more front to back displacement than that. Or am I looking at that wrong?

:oops: Why, yes, I was looking at it wrong or perhaps I should have gone and had an actual look before typing. Thanks, Rohan, for sorting that for me. Makes perfect sense.
Last edited by Bud English on Mon Jan 21, 2019 4:42 pm, edited 1 time in total.
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PostPost by: rgh0 » Mon Jan 21, 2019 8:28 am

The issue is around misalignment of the actual diff output shaft not the total drive shaft to the wheels. It is crtiical that the centreline of the bearing carried in the alloy back housing lines up with the centreline of the diff carrier bearings mounted on the front diff nose as the output shaft is carried by these two bearings

I was not aware that there we two different gasket thicknesses or how tell which you should use. Perhapa Promotor knows more details

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PostPost by: 2cams70 » Mon Jan 21, 2019 10:10 am

Fords only ever used a thin gasket. The thin gasket is fine in a Ford which uses a rigid steel axle housing. The flange of the alloy Lotus housing is likely less rigid and therefore more susceptible to oil leakage particularly if the fasteners have been over torqued in the past. The thicker gasket probably helps circumvent this.
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PostPost by: rgh0 » Mon Jan 21, 2019 7:41 pm

The question is was the Lotus alloy housing dimensioned to use the thin or thick gasket or were there version for either /

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PostPost by: promotor » Mon Jan 21, 2019 9:19 pm

All of the complete Lotus final drives I have overhauled have had the same colour/material thick fibre gasket fitted when I have split the diff nose from the aluminium casing. I have never seen any other gasket fitted. This refers to both early and late type aluminium carriers ie small and large mounting ears.

Whenever I rebuild a complete final drive I always use a thick gasket. They are approx 0.030" thick when new. The paper gaskets as fitted to standard Ford road cars are approx 0.010" thick when new.

My Elan workshop manual - which is a later one and covers up to S4 Elans doesn't make any mention of gasket thickness in the "final drive" section.
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