Long Final Drive?

[hughjames]

Is it possible to have a extra long final drive ratio (even if specially made)? On my Sprint, which is road use only, I have effectively a three speed box. First is of little practical use, and Interstates require too high a cruising engine speed. I know I could install a five spped, but wouls prefer to keep the 2000E box.

[enskr]

I believe all the 4 speed boxes have a 1:1 4th gear. Perhaps you should be looking at the final drive ratio - do you know which one you have? The "longest" fitted by Lotus was 3.55:1, but many people, including myself, have fitted a 3.54:1 differential from the RS2000 escort (much easier too get hold of) . Going from a 3.77:1 to a 3.54:1 made a huge difference to my Elan.

Kevin

[bill308]

hughjames,

I'm afraid Kevin has it about right. Lowest numerical rear drive ratio is 3.55/3.54:1.

If you fit a Lotus close ratio box or gear set you change the first gear ratio from 2.97:1 to 2.51:1 and first gear becomes a lot taller. Intermediate gear ratios become a lot closer also but fourth gear remains the same. 1:1.

Bill

[tyasman]

I agree with Kevin. My diff ran dry on a trip to the Classic Le Mans, so although we got it home (try buying diff oil in France on Bastille day!) it was knackered when we took it out, which meant I had to find a new one, and I had been thinking about a higher final drive ratio for some time. I got a RS 2000 diff on ebay and made sure it was set up properly before I installed it. It's not quite like having a fifth gear, but cruising at 70/80 is much more relaxed. However, taking the old one out is a subject in itself. We followed all the instructions and advice and still had to resort to some hammer work. Got there eventually though! Worth the effort.

[msd1107]

Lotus homologated a 9:31 3.444 differential ratio. Anybody know where to get the 31 tooth ring gear?

Starting with the RS2000 differential (11:39 - 3.545), if you are really adventuresome, try acquiring and installing smaller ring gears. 11:38 gives 3.455. 11:37 gives 3.364. 11:36 gives 3.273. 11:35 gives 3.182. 11:34 gives 3.091. And 11:33 gives 3.00.

If you are using the sedan gearbox with 2.97 1st gear and a 3.55 differential, a 2.996 differential ratio would give a 1st gear with the same speeds in 1st gear as the 2.51 close ratio gearbox and 3.55 diff. However, you probably would not like driving that combination due to the large drop between 3rd and 4th.

Write [email protected] and ask about his 5-speed kit for the Elan, which he claims in a recent email is now available for order.

David
1968 36/7988

[Foxie]

My Plus "S had a std 4 speed and 3.9 diff when I got it

Then I put in a 3.55 diff.

Then I put in a T9 5 speed (0.82 5th) and a 3.77

Then I put back the 3.55

Perfect. Can match modern M-way speeds for hours on end at nice'n easy revs

[bill308]

Thanks for that input Sean. I spec'ed out my T9 with a 0.82 fifth. My Elan always ran with a 3.55 rear but I was agonizing over whether I should fit a 3.77. I think I'll stay with the 3.55 for my use. Interestingly, speeds here keep creeping up. A state trooper passed me on an interstate while I was doing about 75 mph in my clunker today. A fellow driver pulled out behind the trooper and followed him, about 10-car lengths behind and I followed the tailing driver, going maybe 85 mph for perhaps 15-miles.

Bill

[msd1107]

Bill,

Your .82 5th with 155-13 tires and 3.55 diff will give around 146 at 6500. While it is probably academic here in the states, a strong FHC will probably pull that (Consider road tests of S2/S3 SE FHC with 3.55 got to 7000 which is almost 130, with road testers complaining they couldn't get more revs. With proper gearing, that is probably 133-135. So a well modified Twinc should have no trouble getting the last 10-12 mph)

Of more importance is that 80 mph is less than 3600, dreamy compared to the 4300+ now with 1:1 4th.

David
1968 36/7988

[65 Lotus]

I always wanted a long final drive, but with my Irish heritage, it was just not meant to be.

[Foxie]

I always wanted a long final drive, but with my Irish heritage, it was just not meant to be.

Scott,

You'll have to explain that one to me, I can't figure it out

[fatboyoz]

I think he means there is a cemetary just around every corner!
Colin.

I always wanted a long final drive, but with my Irish heritage, it was just not meant to be.

Scott,

You'll have to explain that one to me, I can't figure it out

[Foxie]

I think he means there is a cemetary just around every corner!
Colin.

I always wanted a long final drive, but with my Irish heritage, it was just not meant to be.

Scott,

You'll have to explain that one to me, I can't figure it out

Maybe you're on the right track. But on the other hand, Ohio to Galway Bay would be one helluva Final Drive