Lotus Elan

3.54 differential

PostPost by: 512BB » Mon May 06, 2019 11:25 am

You have been told incorrectly Jeremy. It is a straight swap, the hole spacing and size are the same.

It should be noted that there are 3 flange sizes. 85, 92 and 105mm. The Elan size is the 92mm diameter flange, but I suspect that many have been changed over the years.

Leslie
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PostPost by: rgh0 » Mon May 06, 2019 12:02 pm

I have swapped old Ford non Lotus diff noses with new replacement Lotus rear diff housings or original Lotus diff housings without any problem with bolts between the two.

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PostPost by: prezoom » Mon May 06, 2019 3:06 pm

On my Plus2, I used a 3.9 housing from a Cortina and swapped in a 3.5. Everything bolted together including the larger pinion flange that matched the prop shaft flange that mated to the original 3.7. It appears that the pinion seal leak I currently have, is probably a worn portion of the pinion flange where the seal contacts the flange. Debating the use of a seal saver vs a universal flange from Burtons. My S2 has the smaller flange. I have a new 3.5 ring and pinion to install and another Cortina diff, but need to source a small flange. There was a significant difference in acceleration between the 3.7 and the 3.5 in the Plus2. But, a more relaxed cruising rpm.
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PostPost by: promotor » Mon May 06, 2019 5:03 pm

prezoom wrote:On my Plus2, I used a 3.9 housing from a Cortina and swapped in a 3.5. Everything bolted together including the larger pinion flange that matched the prop shaft flange that mated to the original 3.7. It appears that the pinion seal leak I currently have, is probably a worn portion of the pinion flange where the seal contacts the flange. Debating the use of a seal saver vs a universal flange from Burtons. My S2 has the smaller flange. I have a new 3.5 ring and pinion to install and another Cortina diff, but need to source a small flange. There was a significant difference in acceleration between the 3.7 and the 3.5 in the Plus2. But, a more relaxed cruising rpm.


As far as I'm aware if you buy any new flanges from any company they will not come with a flange shield - this shield is good for two things : 1) stops dirt, girt and water etc getting into the seal face; and, 2) if the diff breather gets blocked a build up of internal pressure may try to blow the seal out - a flange with a shield should stop this happening, or will make a leak not quite as disastrous as one with the seal completely blown out where no shield is fitted.
To get an old shield to fit a new flange is fairly easy but a seal face repair is a much simpler fix.
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PostPost by: Baggy2 » Mon May 06, 2019 7:00 pm

Many thanks for the replies - and so quick !
I've got to the time of life where relaxed cruising is more important than out and out acceleration so the comments regarding that are useful too.
Thanks again
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