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UN1 Holloway reinforced shaft/gears kit available again - group buy - Page 3 - Gearchange/Gearbox/Clutch - The Lotus Forums #ForTheOwners Jump to content

UN1 Holloway reinforced shaft/gears kit available again - group buy

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On 2/27/2016 at 19:59, MikeS2 said:

I would like one as well for my UN1-027. 


Mike, are you referring to the UN1 kit? Please PM me.


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as for 'figure of merit' engineering you have to match material specification, acting forces and momentum  ..and in terms of a automobile the relation between 'engine momentum' curve (think

I can count on one hand how many people have had gearbox problems, it's not a common problem in the slightest.

I saw that I was thinking of those gaskets etc. Jacques.

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This kit fits revised 'Hi Torque' RH shift transmission gear boxes from 1993 and thereafter:  Esprit SE USA from April '93 (w/RH shift transmission) and all of the  S300, S4, S4s, V8, V8GT, 350 and GT3


On 1/18/2016 at 10:24, plumdeplakmuis said:

Dear John,

(You speak Dutch?)

Gearbox is a UN 28 for the GT3. Do you know differences in the shaft cause the upgrade not to fit?

If it is the crown wheel, I'm considering also changing the diff to Quaife LSD, and then installing a new wheel.


Deze kit past herziene 'Hi-Torque' RH shift transmissie versnellingsbakken van 1993 en daarna: Esprit SE VS van April ' 93 (w/RH shift transmissie) en alle S300, S4, S4s, V8, V8GT, 350 en GT3

Als uw transmissie shifters aan rechterkant heeft deze upgrade uw toepassing zal passen.

Hebben een goede dag


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This kit would not fit earlier UN1-s, but there is a hope on the horizon!

Friend of mine, Peter Lenard, decided to independently develop a short ratio gear kit for his UN1-03, just shaft,1st +2nd gear. Although older, yes I believe UN1-03 new parts are quite likely to be a straight fit into the older (pre-S4) SE boxes.

PM me, if you'd like to get more information. [email protected]

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6 hours ago, AzureBalboa02 said:

I'm very interested in ordering one Kit. Please PM me with current details.

Welcome to TLF Patrick. :welcome:

 You should duck over to the Introductions area and say hi in there as well. :)

All we know is that when they stop making this, we will be properly, properly sad.Jeremy Clarkson on the Esprit.

Opinions are like armpits. Everyone has them, some just stink more than others.

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just as a 'technical sidenote' for interested people, those who know me in persion know that I tend to be a teacher sometimes ..sorry for that ;) ..

Renault used to fit the 356/UN-1 boxes in different types of cars, all over the production period as we know. it is logical to have a 'main setup' for the gearshafts with different types of input shafts as add-ons for different flywheel/engine designs in the Renault family. Therefor create the input end as a "slip on" two piece shaft.

From mechanical dynamics, and stress calculation on a shaft a "grove" can smoothen out the hard points in the stress curve (tension curve) - but if placed wrong or fabricated in a bad design (harsh surface step, raw surfaces) can make it even weaker. So it is not bad in general to have a "joint point" on a shaft where a other shaft fits or is contacted.

Sometimes a small step with a harsh radius change just causes a stress load, to interact as the beginning point of a crack line. Especially if you have a notable diameter difference, or a big and stiff object pressed to hard onto a shaft with bad calculated tolerance between bore & shaft (Hx/hx)  - the mentioned EMCO guys will hopefully explain in better english what I mean.


So if you look onto the rear end of the UN-1 gearbox with the overhang gear, keep in mind that there is:

1. way a nut srewed on, so this means tensional load in the shaft axis, to press the bearing/gear and related parts onto the shaft.

Additionally there is the Nm transfered from one shaft to the other. In one time transfered straigt on a rolling car with engine power delivered to the street, on the other situation the driveline and the engine volume with closet trottle acts as brake system, with a car (and its translatoric & rotatoric masses) running into this and slow down. Means the pairing of gears (as well shafts)  has to compensate the load .. and from naturally aspects every gear does have a contact surface with the opposite gear that is under load [if engaged] ..and you know from [technical] shool that every vector of force needs a opposite vector of force to hold. That guides to the effect of gears (gearwheels) who want to get of from each other - but as normaly gears sit on shafts and those shafts are supported by bearings in a main case the gear(wheels) cant's separate  ..  .

If you know have a gear-pairing that is on the "overhung" end of a shaft, so only supported on one side - the overhung tends more to flex [in structural relevant micrometer distance, of course] under load. Now two bad situations are together, you can see them in the well known pictures:

A small diameter step on the shaft, with harsh radius change - where the rear bearing sits on..

The existing Nm torsional load from the engine/driveline power on the gearwheel-contact sufaces..

..and - but that's more or less a issue with garage (or the Renault workshopbook) - a 'overdone' tension rate / tension load from fitting with Nm pretention on the nut, to fit the 5 gear pairing with tools.


**** other sidenote:

It was my car with a "harsh wear" on the spline of the input shaft - but this problem was (is still) not the spline for the 'two piece joint' is the spline for the clutch plates .. as Renault used what I would call "mouse tooth"  profile type that does not hold on for that hard loads of trackday and / or 918 power capabilitys.  Therefore the not so 'hard' surface preparation on the AP-clutch plates weared out as well  .. two weared profile flanges can slip over and "twist" easy  - means no power transfer anymore, and if you park the car and stop the engine, with clutch pedall still pressed you could hear the clutch plates still rotate with rest of rotational energy and "wear of" the rest of the toth profile on the plates. Even metall flakes from the shread shaft profile had fallen off from the openig on the clutch housing underside..

If you study engineering you lean what it means, lets say the difference between a splinetooth with \/ - profile and a \__/ -profile ..until the 'contact hight' is reduced on the profile-shoulders..  :)

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to name the things if I see them, that's what I call integrity..


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As it looks, the pictures shown, are from the old D.Bell page .. I would guess 

..and there on his old page was a 'note' that he thanks Ramspott & Brand in Germany for the pictures   .. and guess who has the remained main part of the broken shaft pictured there on his desk at home ?  ;)   

.. I've got it from Steffen and Olaf and used it for a technical discussion in the university several years ago.


The details of a crack and structural problems can be seen on the surface, and looks of the exposed structure, that's why the Professor was interested as well to see this part as example and reference for the topic.


to name the things if I see them, that's what I call integrity..


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Last call, guys! Not too late to join.

Will be closing the List pretty soon!

Expected delivery in early July.

So, if you're still undecided... the time is now!

These kits won't be available again anytime soon.

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John, I tried to PM you but it says you cannot receive messages.

What is the price of the kits and when will the order close and be placed to the manufacturer?


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This kit fits:
UN1 – 026 – High Torque G/Box – Stronger Casings etc. introduced in April/May 1993, so it’ll fit some late SE-s.  This 'Box had rear cover with right hand shift lever

UN1 – 027 – V8 Gearbox – Introduced in 1996 on V8 Esprit. Similar to 4 Cyl High Torque units with new Clutch Housing. It carried over the R/H shift lever.

Testimonial from  Stugilmour:  Holloway kit decreased first gear ratio addressing synchronization engagement issue. The first gear is 'taller' than stock, so it is a bit harder on take-off.
That said, the change in the Holloway first gear is less than the GTO-Racing kit, so it is suggested it is more suited to the four cylinder cars. I have the GTO-Racing kit installed, and the V8 has absolutely no issue with the taller first, taking off easily with no stalling or whatever.

Looking the summary over, I think all the fourth gear ratio's should be identical at 1.04, but GTO-Racing had 0.96 on their web site at the time.
Gear Ratio Summary Table
.......................Stock..............Upgrade. ................Upgrade
First................ 3.36. .............. 3.00 ..................... 2.66
Second........... 2.06 ............... 1.94 ..................... 1.75
Third.............. 1.38 ......
Fourth............ 1.04 ........
Fifth............... 0.82 .........
Reverse.......... 3.54

On our Elan Forum there is a member who is expert in transmission ratio design. He has prepared a giant spreadsheet that gives a 'Figure of Merit' to the transmission ratios. The Holloway ratio's for first through fourth get the highest rating of 100. The large space to fifth brings it down to -87; the spreadsheet says 0.81 would be the ideal fifth for progressive feel. That said, not an issue in the real world as fifth is just used to cruise anyway. For comparison, the stock first through fourth only get a FOM of -4 and the GTO-Racing FOM is a -472.

Anyway, the whole point is the Holloway ratio selection is much better for synchro rings durability/longevity.

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as for 'figure of merit' engineering you have to match material specification, acting forces and momentum  ..and in terms of a automobile the relation between 'engine momentum' curve (think about power output and rpm) vs. 'motion resistance' curve (think about the exponential rise of resistance force against a car on rise of speed). Main target is to find a gearing set that holds the most effective rpm-point of a engine and the momentum-curve of that near to the 'resistance momentum' of speed.  ..if this is the right way to say it in english

Means for every model of car it needs a specific set.  So this mentioned spreadsheet above needs to have at least a number of different pages, for V8 and additionally all the different power curves on the 4pot cars, since introduction of the Renault box  .. 


Anyway - as long as the main problems and weak points are adressed it should be good, GTO or Holloway as well.

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to name the things if I see them, that's what I call integrity..


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One person bailed out due to job/financial reasons, so I have an extra kit.
Please PM me if you want it
(even if you were not on the Group Buy List).


UN1-026/27 single shaft upgrade kit decreased first gear ratio focusing on addressing synchronization engagement issue. It did not drop the first gear ratio as extremely as Quaife/GTO kit. This makes EMCO kit more friendly for lower torque 4 cylinder engines.
EMCO Kit...      ......GTO
1-st   3.0 ..... vs.  .. ( 2.66)
2-nd 1.94 ......vs. . (1.75)

Edited by MrDangerUS
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