Lotus Elan

Propshaft Blues (diff flange size)

PostPost by: holywood3645 » Wed May 17, 2017 12:41 am

I have a 3.5 diff that I have been waiting to fit to may S4 elan. Recently while working to install CV drive shafts, i decided to install the 3.5 diff. Now i have it in place, i find out the prop shalt end bolt spacing is larger (the newly installed 3.5 diff has smaller bolt spacing) than the diff I removed.

I good freind 'Prezoom' has suggested th change the back portion on the prop shaft. This sounds like the easiest fix, however i need to source the smaller prop shaft to diff piece
Any ideas I have looked at the TT site in UK and he has a PINION FLANGE drilled for both size props.
Does anyone have a spare small bolt spacing part of the prop that connects to the diff? or have any other suggestions?

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PostPost by: jono » Wed May 17, 2017 6:41 am

I recently had exactly same experience when reverting back to a 3.77.

The new diff unit has a different PCD on the flange. I ended up swapping the flange from the existing diff onto the new unit. I was worried about the preload as I'd already built up the new diff with new bearings and seals but I just torqued it to the factory setting, checked it for 'feel', and all was fine.

Personally I would keep the prop as it is in case you alter the balance/phasing by changing the rear flange.

Until then I never realised there are different flanges on the diffs

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PostPost by: promotor » Wed May 17, 2017 7:11 am

If you decide to change the prop flange I have an 86mm O.D. one. I think S4's originally came with a 92mm one though so it all depends on originality of your car. I guess you've got a 108mm one that is causing you the issue?

The other issue may be that I'm in UK and that I'm looking for ?35 for the flange + postage.

No worries if you're not interested. Just a thought.

Regarding the TTR diff flanges they don't come with a seal shield and need modifying if you want to use one - I did this recently - please see here : lotus-gearbox-f37/gearbox-and-diff-rebuild-recommended-suppliers-t39157.html
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PostPost by: gjz30075 » Wed May 17, 2017 9:30 am

James, I have one from an MGB shaft. I believe its the one you need. PM me with your address
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PostPost by: worzel » Wed May 17, 2017 11:28 am

Hi James

If you reside in a biggish city just check out the local specialists- propshaft work is still big business despite the proliferation of front drive cars.

Should cost you around ?30 or so inc fitting.


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PostPost by: Davidb » Wed May 17, 2017 3:47 pm

I did exactly as Jono did. Installed the correct flange after setting up with the incorrect flange-everything worked out fine-the diff is quiet and the oil was relatively clean when I changed it last night after 1200 odd miles.
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PostPost by: bill308 » Wed May 17, 2017 4:28 pm

Hi James,

I have the small prop shaft flange fitted to a diff flange drilled for both the small and large bolt patterns.

I'd be willing to do an even swap if that is of interest to you.

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PostPost by: holywood3645 » Wed May 17, 2017 5:03 pm

Thanks for all the replies.
I think I have a solution that will work.
I do appreciate all the offers
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