The Lotus Grand Tourers

So I got under the car today 4 terns of the prop =just under 2 tern of the wheel approx 4"short at the risk of sounding silly I think it is 3.9 ratio ,advice welcome

I'm assuming you only have one wheel in the air, so the ration will appear to half.
My understanding though is that 4.1 relates to prop shaft and 1 to the wheel in a 4.1:1 ratio. So you have just over 2 turns of prop for one full wheel turn, hence a 4.1 ratio (as would be original on an 84 car).

Yes I'm up on one wheel ,it a pain but marked prop lot of slack in differential your old differential is getting more attractive, where are you approximately to me I'm billericay essex

MetBlue wrote: Sat Jun 21, 2025 10:02 Early cars were 4.1:1, later cars changed to 3.9:1. An 84 car will be 4.1.
Auto's were 3.7:1.

If you have a provenance certificate, it will tell you the serial no for the diff. Suffix A is 4.1, Suffix B is 3.9. Must be marked on the diff somewhere, but no idea were and doubtful still legible after 40 years.

So Tony i think it may be your differential that is the best choice as it is tested ,have you a price in mind ,in the meantime I will fill mine with some gear aid products any suggestions welcome thanks in advance Dave

So Tony i think it may be your differential that is the best choice

I'll PM you my phone number Dave. It's complicated as the 4.1 diff I have is waiting to be fitted to my car after LITP this weekend ( isolation bushes and repairing the crack in the diff carrier the driver).
Then I want to redo the seals in my OE diff, then swop 'em back as my car uses the 3.9 diff as standard, and although I like the idea of a little more surge off the line, I think I prefer the idea of lower revs at motorway speeds.
If I have a reason to do quickish though, no reason why I can't have a spare diff within a month or so from now. It might actually motivate me to complete the job quickly

Tony

I will phone you Tuesday evening and we can go from there .thanks Dave

Where can I request a provenance certificate? Many thanks!

Schrowi wrote: Sun Jul 06, 2025 16:11 Where can I request a provenance certificate? Many thanks!

Contact Andy Graham at Lotus. You can get the full blown one via TLF - https://shop.thelotusforums.com/product ... provenance

Not sure if available, but used to be able to get just the certificate without all the parafinalia for a sensible price.

Just the stuff you need, none of the balls.

https://shop.thelotusforums.com/product ... provenance