Lotus Elan

Close Ratio Propshaft Length

PostPost by: Mazzini » Fri Apr 20, 2018 5:50 pm

Anybody have the dimensions for an early Elan propshaft? I know they were shorter than the later props, but I can't find a number for them.
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PostPost by: elanfan1 » Fri Apr 20, 2018 5:57 pm

As you know I?m not a technical person but a CR gearbox has the same casing as a semi close I believe so it ought to be the same. Ducks for cover.
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PostPost by: bigvalvehead » Fri Apr 20, 2018 6:37 pm

Why would the props be shorter?

I was under the imprssion they were all the same with any minor differences being taken care of by the sliding spline on the front yoke?

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PostPost by: Mazzini » Fri Apr 20, 2018 7:19 pm

Two different lengths, pretty sure of it, will check the parts book for PN's. Don't forget the bellhousing remained the same, but the main case and the tailshaft design changed during the production run, but I think this was to do with the actual gears, the CR ratios weren't made by Ford, but another company...oh and there are two different size spigot bearings as well. I'm sure Al will be along in a bit to put us right.
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PostPost by: Craven » Fri Apr 20, 2018 7:55 pm

Both CR and ?2000E? were gear sets fitted to the standard gear box.
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PostPost by: promotor » Fri Apr 20, 2018 8:00 pm

Hi Rob, I hope you are making progress on your cars.

Wide, semi-close, close and ultra-close gearboxes are all the same length as they are based on the 1200/1500 cortina gearbox. The only Ford 3 rail gearbox that is shorter is the 997 Anglia gearbox (one with crash first gear). There are different tail case designs, but lengths are the same for all of the 1200/1500 cortina and therefore Elan gearboxes.

All gearboxes of the 3 rail variety (including 997) use the same splines for the output shaft.

Of the 2.5 gearboxes I have seen I have only seen a 17mm input shaft nose and I don't believe they were available with a 15mm nose from the factory.

I think the 2.5 gears weren't made by Ford but made by the same company that Ford used to make their wide, semi-close and ultra-close gearsets, and as such the 2.5 (ie close ratio) are designed to work with the Ford gearbox parts that the close ratio gearbox used.
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PostPost by: Mazzini » Fri Apr 20, 2018 8:10 pm

http://www.lotuselan.net/wiki/RA_-_Prop_Shaft

They are different lengths, I have had them in my hands and put them side by side. The reason I'm asking the question is that I want to make sure I put the right one back into my S3.

About thirty years ago I bought a prop from Miles Wilkins and he asked me the question - which length?

The attachment is from the first Elan parts book from '66
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PostPost by: promotor » Fri Apr 20, 2018 8:33 pm

So as we've established that the gearbox casings aren't different lengths, what could be the reason for a different length propshaft if the chassis' all have the same dimensions between the s1-s4 Elans and thus the engine, gearbox and final drive units are all in the same place?

EDIT - what is a "rally ratio" gearbox as per that parts list? That's a new one on me!
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PostPost by: Mazzini » Fri Apr 20, 2018 8:48 pm

Al, have you measured the length of the tail shaft with the early mount compared to the later mount?

"Rally ratio" I guess is the '2000E' or GT ratios, whatever Lotus used after the CR box, they just hadn't found a name for it yet.
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PostPost by: promotor » Fri Apr 20, 2018 9:00 pm

I will check what stock I have tomorrow for you. I have an s1 tailcasing with the ribbed/strengthened edges and flat mount face, and also the later type one on the gearbox I had from you.

I don't think I've got a standard mk1 1200/1500 cortina casing ie the same as is on your 2.5 gearbox but will have a good look around.
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PostPost by: Mazzini » Fri Apr 20, 2018 9:51 pm

Outstanding work on the diff and gearbox by the way - thank you.
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PostPost by: Craven » Sat Apr 21, 2018 12:00 am

Can?t see why tail case would make a difference,
Laygear same length although thrust bearings are radial needle rollers.
All use 105E bell housing.
CR gearbox uses the early main shaft with a sleeved 1st gear but no reason to believe it?s a different length.
Were CR?s built up in alloy cases ?
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PostPost by: prezoom » Sat Apr 21, 2018 12:51 am

I just exchanged a mid close (2.9) for a close ratio (2.5) in my Plus2. The differences I found were, a different diameter input shaft seal at the bearing retainer, and a wedge type transmission mount verses a flat mount. The standard Plus2 drive shaft fit without problems. A lot of measuring was done for the change, as I am using a concentric clutch throwout bearing and made a new bearing retainer to space the Ford Contour/Mondaeo slave and bearing correctly with the Zetec clutch housing and Mitsubishi 3000GT, normally aspirated, friction disc. The new gearbox is coupled with a 3.54 differential and I am loving every minute of it.
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PostPost by: rgh0 » Sat Apr 21, 2018 4:33 am

The only difference between shafts I have ever come across is the small or larger bolt pitch circle for the rear end yoke connection to the diff. The different yoke may have been slightly different in length but any difference in length is taken up by the sliding spline.

I also dont know how accurately the lotus shafts were made and perhaps over the years they changed a little which could result in two different shafts being a slightly different length?

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PostPost by: Mazzini » Sat Apr 21, 2018 7:50 am

Craven wrote:Can?t see why tail case would make a difference,
Laygear same length although thrust bearings are radial needle rollers.
All use 105E bell housing.
CR gearbox uses the early main shaft with a sleeved 1st gear but no reason to believe it?s a different length.
Were CR?s built up in alloy cases ?


They were alloy bellhousings and tailshafts for the Lotus Cortinas (also extension arms) and 26R's, road going Elan's were cast iron. The main case I believe was always cast iron, I think alloy was tried but found to be not suitable.
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