Lotus Elan

4 speed gearbox ratios

PostPost by: JJDraper » Wed Aug 01, 2007 9:41 pm

I had a little run (tour) up a hillclimb last Sunday and (apart from realising how slow I am) it was evident that there is a huge gap between second gear and third. As I have no experience of other +2s I wondered if this is common to all 4 speed 'boxes. On the road it is not such a problem, but up a steep hill..... My diff is a standard 3.77.

Any thoughts out there? Has my box been butchered, or are they all like that?!

Jeremy
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PostPost by: Dag-Henning » Thu Aug 02, 2007 5:08 pm

- maybe your Lotus-box has been replaced with a std. Cortina box once upon a time.......They had a huge (!) gap between 2nd and 3rd as you describe, before the 2000E-ratios came....My wilde guess.......!

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PostPost by: peterako » Thu Aug 02, 2007 6:41 pm

Hi Jeremy,

My only comment would be that I have no such gap
between 2nd and 3rd.

Though I'm on a 5 speed box 1 to 4 are the same (I think) as
the four speed box as far as ratios are concerned.

1 to 4 on my box all have ROUGHLY the same gap, which suits the
engine and diff very well (I'm pretty sure I'm on 3.77 too).
5 is a jump (20% less revs than 4 for the same speed.)

Take care,
Peter 1973 +2S 130/5, looking better now I've discovered laquer....or is that Liquor?
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PostPost by: oldokie » Thu Aug 02, 2007 7:13 pm

My +2 has a gap, 2/3, my Elan's 2/3 is much closer, the MII Cortina GT I once owned was closer than +2 but wider than Elan, I think there are 4 sets in common usage, close ratio, semi close (my Elan), Cortina, and Estate(my +2). I bet Rohan can clear this up for us!
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PostPost by: types26/36 » Thu Aug 02, 2007 7:45 pm

The Elans (well from about the S2's) not sure exactly when were fitted with the 2000E ratio's (first fitted to the Cosair 2000GT) these ratio's were in several Ford boxes with various style of gearbox. When these ratios were fitted the box had a I.D. tag with 2821E, these tags get broken off or left off but it is possible that it is still on.
Try looking on the box to see if the tag is still there, it should be on one of the bolts holding the tail housing to the main gear box.
Here is a chart showing the g/boxes fitted to various cars.
http://freespace.virgin.net/tommy.sandh ... d%20Ratios
Brian
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PostPost by: msd1107 » Sat Aug 04, 2007 8:45 pm

The 4-speed Elans have used three different gearbox ratio sets. The very early Elan+0 used (17/32, 22/28, 28/21) 17/32 gears for 3.54, 2.39, 1.41, and 1.00 ratios. Very few Elans have this box.

The next ratio set was used from the Cortina rally program and used (17/32, 22/27, 26/24) 21/28 gears for 2.51, 1.64, 1.23, and 1.0 ratios together with a 3.9 differential. This has been described as "close ratio" or "ultra close ratio".

With the SE came the last ratio set using (17/32, 22/28, 26/23) 19/30 gears for 2.97, 2.01, 1.39, and 1.0 ratios with a 3.55 differential. This has been described as "semi-close ratio" or "mid-close ratio".

Later Elan +0 used a 3.77 differential with this ratio set, as did +2. The 3.55 and 3.9 differentials and 2.51 transmission ostensibly were available to special order.

Over the years, it is hard to tell what transmission and ratio set may have been retrofitted. There is a 3.65, 1.97, 1.37, 1.00 ratio set that was in some of the sedan boxes.

You can get a rough estimate of your actual ratios by running the car up to the same RPM in each gear and noting the speed. Then compute the ratios. See which one is closest to a published set.

On the standard 2.97 box, 1st to 2nd will feel relatively close, 2nd to 3rd will feel a wider, and 3rd to 4th will feel wider still.

http://www.lotuselan.net/forums/viewtopic.php?t=15049 has a downloadable spreadsheet that you can use.

And if you are really curious, email me and I can send you another spreadsheet (much too large to post) that might answer questions you never thought to ask about gear ratio design. Not for the faint hearted.

David
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PostPost by: iain.hamlton » Mon Aug 06, 2007 10:48 am

Jeremy,

as others have said, there are several ratios you may have, but whether the gap is too large is somewhat subjective. Had you thought of working out what ratios you have? If your speedo and rev-counter are something like right, you could measure your mph/1000 (at say, 3000 rpm) in each gear, and do the arithmetic. As top is one-to-one, you only need to work out ratios from that; you do not need to consider rolling radius and diff ratio.

Also, suggest you talk to some other Hillclimb specialists. for instance, Roy Fellows at Paul Matty's competes in a +2, and uses a lower diff-ratio (this gives torque at the wheels in third, even if 2nd runs out even quicker). I think Roy also uses a close ratio gear box.

best regards, iain
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