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Lotus Europa Forums => Garage => Topic started by: 1970S2 on Tuesday,December 14, 2021, 07:28:40 AM

Title: gear ratio for differential 32T or 34T ?
Post by: 1970S2 on Tuesday,December 14, 2021, 07:28:40 AM
I have 2 ratios available to use, 34T or 32T.....the Europa came with a 32T =3:55 ratio , the 34T =3:77 ratio...i'm using stock tire, i'm thinking a better holeshot on track, possible loss of top end speed.....any thoughts ?.....anyone else tried this combo?
Title: Re: gear ratio for differential 32T or 34T ?
Post by: SwiftDB4 on Tuesday,December 14, 2021, 08:15:38 AM
Is this a 336 4 speed? Some other 5 speed? Are you saying just change the crown wheel, but not the pinion? On Europas I would tend to say get as low a r/p as possible otherwise 1st gear is worthless and top gear too low.
Title: Re: gear ratio for differential 32T or 34T ?
Post by: jbcollier on Tuesday,December 14, 2021, 04:36:25 PM
Can you explain how you have the two final drive ratios?  The 3.56 is a Lotus only ratio that Renault made for them.  It allows the R16 336 to turn the other way.  It fits the 336 and 352 boxes.  The 3.78 ratio is a standard Renault ratio and is used in the 365.
Title: Re: gear ratio for differential 32T or 34T ?
Post by: 1970S2 on Wednesday,December 15, 2021, 02:31:44 PM
I have 2 transmissions, both 336, one has 34T crown from an R16, the original Europa has the 32T, crown and pinions are macthed sets 9 x 32 and 9x 34.....the 34 is in way better condition, I'm thinking of just putting a taller tire on the rear....thoughts ?
Title: Re: gear ratio for differential 32T or 34T ?
Post by: jbcollier on Wednesday,December 15, 2021, 04:45:07 PM
The R16 Crown and pinion turn the other way, unfortunately.  Though it looks like you may be able to flip them, you can’t as the diff is “slightly” hypoid.  So, you need to use the 3.56 ratio.  If it is in bad shape, you can ask around for a used set.
Title: Re: gear ratio for differential 32T or 34T ?
Post by: 1970S2 on Wednesday,December 15, 2021, 06:23:18 PM
the crown gear can go on either side of the gearbox, that's how you change the direction of rotation they are identical
Title: Re: gear ratio for differential 32T or 34T ?
Post by: GavinT on Wednesday,December 15, 2021, 06:43:17 PM
Quote from: 1970S2 on Wednesday,December 15, 2021, 06:23:18 PM
the crown gear can go on either side of the gearbox, that's how you change the direction of rotation they are identical
Sorry, no. The crown wheel and pinion shaft axis are not on the same centreline.
i.e. one is higher than the other as viewed from the side (I forget which)

That's why you can't simply flip the crown wheel.
Title: Re: gear ratio for differential 32T or 34T ?
Post by: 1970S2 on Wednesday,December 15, 2021, 06:57:15 PM
so your telling me that if I change just the crown gear onto the Europa diff carrier it won't work ?
Title: Re: gear ratio for differential 32T or 34T ?
Post by: jbcollier on Wednesday,December 15, 2021, 08:51:10 PM
Yes, the ring gear can only go on one side.

Wish you could just flip 'em.
Title: Re: gear ratio for differential 32T or 34T ?
Post by: MRN I J on Thursday,December 16, 2021, 08:45:12 AM
they need to be a matched pinion / cwp set aswell
Title: Re: gear ratio for differential 32T or 34T ?
Post by: GavinT on Thursday,December 16, 2021, 04:54:24 PM
Thought experiment:

Imagine rotating the crown wheel so that it ends up on the other side of the pinion.
It should be observed the centre line offset dictates the placement of the components.