Lotus Elan

5 speed gearbox conversion

PostPost by: sgbooth » Sun Mar 12, 2006 7:37 pm

I'm considering a 5 speed gearbox conversion/upgrade using the +2 box.

Does anyone have any experience/opinion regarding regarding "how to" or "performance" issues?

Mine's a'71 Sprint. What else might I need (ie propshaft) etc?

Regards,

Stuart.
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PostPost by: john.p.clegg » Mon Mar 13, 2006 4:12 pm

Different clutch pressure plate if you have the one with an insert.
Different clutch friction plate.
Different propshaft.
Apart from that it is easy-peasey if the box comes with its mounting plate.
For all that effort you get a useful reduction in first gear of about 8% along with a useful increase over top gear of 10%

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PostPost by: ppnelan » Mon Mar 13, 2006 5:25 pm

Stuart,

You also need a boss that carries the input shaft bearing in the end of the crankshaft/flywheel, as the input shaft is shorter (but the bearing is the same).
If you have a Lotus Replacement chassis, the mounting holes for the 5-speed gearbox bracket should be there already.
I think the speedo cable may be different to the 4-speed too.

There's an excellent article about rebuilding the 5-speed gearbox for use in an Elan at
http://www.gglotus.org/ggtech/elan-5spd/elan5spd.pdf
or in the Lotus Drivers Club magazine Iss.70 (2003)

Kind regards,
Matthew
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PostPost by: seaandmoor » Mon Mar 13, 2006 9:27 pm

Hiya,
I could be in a position to part with my 5spd box which would of course have the correct plate and the different length driveshaft required for the whole job as I'm doing something different. It comes off a late 1973 and was rebuilt about 1000 miles ago as part of other work whilst the engine was out having only done 56K.
I'll probably be placing it for sale on here in a few weeks time anyway.
Good luck with whatever you decide.
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PostPost by: lotuselan2 » Mon Mar 13, 2006 11:56 pm

Hiya
I would be interested in the 5-speed to go in my +2. Do I need any of the other pieces to convert my +2? I know the prop shaft is of no use to me, but will I need to change mine?

When ready to sell, please send your asking price to me. <[email protected]>.
Ken
'69 Lotus Elan +2 with Cosworth BDR
'84 Ferrari 400i
'94 Subaru SVX
'04 Audi allroad
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PostPost by: sgbooth » Tue Mar 14, 2006 6:04 am

Many thanks for all the information ......... much appreciated.

Seaandmoor:

I've sent you a pm.

Regards,

Stuart.
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PostPost by: sk178ta » Tue Mar 14, 2006 9:16 am

I`ve put the engine and 5 speed from a +2S/5 in my S3 Elan with only the propshaft needing shortening. I was initially hugely disappointed with the quality of the gear change but replaced the rubber bush gear lever mounting with a direct bolt. This transformed the change with scarcelyany extra noise or vibration. The change from 4th to 5th and back is a little awkward but the revised gearing is well worthwhile.
Jim
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PostPost by: ppnelan » Tue Mar 14, 2006 9:32 am

Ken (lotuselan2),

The propshafts for 4-speed & 5-speed gearboxes are different, even on a +2. The 5-speed one has a sliding spline joint in the shaft between the u-j's, while the 4-speed has a spline in the end where it mates with the gearbox. See p.169 of the Robinshaw & Ross book (1995).

Kind regards,
:arrow: Matthew
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PostPost by: rgh0 » Tue Mar 14, 2006 9:37 am

A couple of further minor comments

While the clutch friction plate is different between the 4 speed which was orginally 8 inch in diameter and the 5 speed which was 8.5 inches diameter they are in fact interchangeable as either fits either of the clutch pressure plates and they have the same spline and inner hub dimensions. The 8 inch plate is actually sufficient for all normal and most abnormal needs so you dont really need to change it. If you go for the 8.5 inch plate there are 2 different types around one with 6 springs and one with 4. If have seen the 4 spring type fail prematurely due to cracking around where the spring openings are formed in the plate so use the six spring type if you can.

The reverse light switch is also in a different location in the lower left rear corner of the 5 speed box and thus the wiring needs to be extended to reach it.

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PostPost by: john.p.clegg » Tue Mar 14, 2006 1:14 pm

Rohan
Beg to differ but the splines on 4 and 5 speed boxes are different in number of teeth and diameter(in my humble oppinion-not wanting to upset anyone).
Tongue in cheek

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PostPost by: alaric » Tue Mar 14, 2006 8:26 pm

From my experience / saga of converting the +2S 130/5 to use a T9 box;

Flywheel insert - this converts the 4 speed equipped engine into one that'll accept the 5 speed box input shaft.
5 speed non pressure pad version of the clutch diaphram spring.
Clutch plate - assuming the splines are different between the 4 speed and 5 speed boxes.
Rounded thrust bearing to go with the diaphram spring.
Gearbox mounting bracket.
+2 5 speed prop shaft - with the integral sliding spline and a flange at the front that looks that the one at the back.
Maybe the clutch actuation lever etc - not sure about this.
A gearbox.

I have everything that you would need in the garage. The thrust bearing, clutch plate, diaphram spring, actuator clips, clutch slave cylinder and its output shaft, and the gearbox bracket are all new. Happy to help out identifying bits etc - I can make measurements and send photos etc. I will want to sell it all at some point, but not for a couple of months.

Sean.
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PostPost by: rgh0 » Wed Mar 15, 2006 9:13 am

John

I have a clutch friction plate out of my standard 5 speed plus 2 currently running in a standard 4 speed box in a twin cam S4 Seven. I also compared it to the splines in my spare 4 speed box out of my Elan before putting it in the Seven. So I know the splines are the same and they are interchangeable.

So unless these "standard" boxes have been modified by some unknown person in the past which I dont believe is the case the splines in at least these 3 boxes are the same.

Happy to be proved wrong but it works for me
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PostPost by: john.p.clegg » Wed Mar 15, 2006 9:28 am

Rohan
Have just been out to the shed(it's freezing out there)and the two shafts measure 1 1/16 25 splines -5 speed
7/8 20 splines -4 speed
Maybe we need a third party to settle this?

John :wink:
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PostPost by: rgh0 » Wed Mar 15, 2006 9:50 am

John

Much nicer in my garage at a pleasant 25 degrees C. Though it was 39 C last Saturday when I was finishing up the routine service on the plus2.

The 5 speed is in the car so I cant recheck, but the plate that went into the 4 speed came out of the 5 speed. May be Lotus made a couple of different versions of input shaft.

Up until a few months ago I had always assumed they were different based on peoples comments but when a friend had a failure at a local race meeting of the 4 speed clutch in his Seven a quick checked showed my old spare 5 speed plate would fit and a quick clutch change on Saturday night got him back in the race for Sunday

Interesting if its another undocumented change.

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PostPost by: john.p.clegg » Wed Mar 15, 2006 10:01 am

Rohan
The only way I can get out of this is the fact that two of the boxes I have got seem to have come from the elite,maybe there are two different input shafts?-seems silly but colin has been known to do stranger things if saving costs was involve,but for the life of me I cant see how anyone could save money making two different types?

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