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UN1 Upgrade Thread - Gearchange/Gearbox/Clutch - The Lotus Forums Jump to content
karmavore

UN1 Upgrade Thread

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I wondering if you all could help me enumerate the different options for UN1 upgrades along with their approximate costs, benefits, downsides, as well as any personal experiences.

In my quest to resurrect Lady Jane I may decided to get into a gearbox rebuild and "while I'm in there…"

Any help is appreciated!

Edited by karmavore

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Upgrade today to remove Google ads and support TLF.

Also contact Mick at Southern GT40 as he has rebuilt UN1 gearboxes in stock which are capable of huge ammounts of power also i think they have limited slip diff. Cant remember but hes not expensive either

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Lucas did you see my posts yesterday about Albins?

In Australian dollars they charge $990 for their stronger "short" mainshaft. When I last spoke with Steve there they hadn't costed their one-piece mainshaft but were thinking around $1500.

If the gearing is to be changed then each gear is $500. 3rd, 4th and 5th being pairs would be $1000 per ratio. 1st and 2nd are cheaper because the atching gears are cut on the mainshaft.Their crownwheel and pinions are around $2500.

As for ratio they have quite an assortment of various ones a customer can select.

The dog gears are the same charge but do reuirq a different hub and slider which is around $600 per pair of gears.

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Lucas did you see my posts yesterday about Albins?

I did. In fact it is what inspired me to start an Upgrade FAQ. It sounds like a much more economical option than the others. $9K for parts is not in my budget at the moment!

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Whatever you do with the gearbox, always remember that the clutch is total crap. Higher ratio first gear will expose the inherent judder in the clutch and a chain is only as strong as the weakest link. I think that the twin plate clutch was probably designed on a Friday afternoon in 1923 and made out of left over cheese and bacon. All this said, the higher ratio close ratio 'box that GTO do is marvellous once the car is moving. Better shift, better acceleration through the gears and 500 bhp plus capability. (oh and an LSD) I have gone back to the standard box but mine still judders. Having lived with both for years, I would certainly go back to Kevin's 'box. I only wish they would do the same for the clutch as they did for the springs and dampers! One of the reasons that the taller ratio 'box was better was that you could put it in second at 15mph and then take it out beyond the legal limit without having to change gear!

And...What is more...My red vacuum hose from the wastegates fell off a few months ago. This meant that there was no boost control. There was no fuel cut out at any stage and so I presume that there wasn't a ridiculous amount of overboost, but the performance was stunning. It was the closest drive to a Murcielago I have experienced. Without the taller gearbox it would have been hopeless (and without the 1 piece shaft, probably broken as well!)

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What do you want out of the gearbox ?

Are you upping power - keep in mind not many V8's have wreaked the boxes, I've NEVER heard of a 4 pot doing it.

The only thing I would go on if I had the cash is a 6 speed.

The other things you might wanna do is upgrade to the later shifter design (did I say shifter, I mean gear change lol) and slightly radius the selector shafts where the ball bearing locks in gear, this mittigates the clunkiness somewhat.

A LSD might help you if you're pulling 300hp.

1 Pieces primary shaft is nice, but the cost !!!!

Unless you're pulling V8 style + torque I would leave it be - Neal on here runs/tracks a ~385hp V8 and iirc has a standard box.

Edited by Jonathan

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What do you want out of the gearbox ?

Good question, Johnathan..

What I wanted from this thread was to have a consilidated list of options and reviews from the community. Unforuntily, since I can't edit my origional post this has become difficult.

What I want for my gearbox is cleaner shifts (it's not that bad, really, expcept getting to 1st and R and the 1 to 2 shift), and something don't feel I have to "baby" all the time. You're right though, $5000 for a sold shaft is shockingly expensive and not in my budget (or under my cost-benifit curve) at the moment.

Thanks as always, boss,

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Good question, Johnathan..

What I wanted from this thread was to have a consilidated list of options and reviews from the community. Unforuntily, since I can't edit my origional post this has become difficult.

What I want for my gearbox is cleaner shifts (it's not that bad, really, expcept getting to 1st and R and the 1 to 2 shift), and something don't feel I have to "baby" all the time. You're right though, $5000 for a sold shaft is shockingly expensive and not in my budget (or under my cost-benifit curve) at the moment.

Thanks as always, boss,

Might want to try contacting GTO, got a quote for a LSD and the main shaft, 1st & 2nd gear upgrade. Very reasonable at the moment. GTO

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The gearbox imo was always to do with the rear translator and the selector shafts.

Lotus updated the rear translator 3 times ?

My SE has the 1st incarnation, my GT3 has the 2nd - not driven a 3rd but a lot of the slop and feel comes from there - refurbing the front and the rear shifter translators will improve the feel (depending on how bad it is now). Also adjusting the rod ends helps a lot with selection - finally change the clutch fluid / slave cylinder - done that on the GT3 recently and it's improved things a lot becuase the clutch has no drag on it - disengage is nice and crisp :)

The next job is the selectors, when I took my SE box apart ....

http://www.flickr.com/photos/jonhimself/sets/72157619525054983/

.... I looked at ways to improve it but found even on the bench the thing was clunky and wooden - this is largely to do (IMO) with the selector shafts and their locators. Basically the shafts have ground recesses made in them and a ball bearing on a tight spring pushes into the recess to hold the shaft in gear, if the recesses are radiused off slightly you have a better transition between out of gear and in gear - if you know what I mean - however radius it too much and you wont stay in gear at all (it litterally just needs de-burring).

The end conclusion I can to was, oh well live with it - refurb the translators (bearings, rod ends etc) and go with it.

There are ways of improving the primary input selector (the one that runs east to west on the gearbox straight from the translator) so it doesn't flex as well - but anything over $500 spent you're not going to see a huge improvement on the feel of the box and tbh the money is better spend on other areas.......in my opinion

Unless you're pushing past 300hp + more torque I dont think I'd bother with an LSD or shaft changes - just dont see you'll see the return in $$ you spend for it (apart form peace at mind ?)

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I've driven an Esprit (89SE and 91 X180-R) with and without LSD on street and track (back to back) and I can tell you the LSD makes a big difference. So much so that I bought an LSD from GTO for my 89SE.

Now for the street, it may not make enough of a difference for normal driving...

Though I also put one in my front wheel drive Honda Integra (Acura RSX here) and I love the difference! I would do it again in an instant.

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I've driven an Esprit (89SE and 91 X180-R) with and without LSD on street and track (back to back) and I can tell you the LSD makes a big difference.

Different how?

Unless you're pushing past 300hp + more torque I dont think I'd bother with an LSD or shaft changes - just dont see you'll see the return in $ you spend for it (apart form peace at mind ?)

If I don't see 300+HP when this is all done I'll be really disappointed!

Thanks for the thoughtful reply, Jon!!

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Different how?

Different as in the level of grip and controllability of the yaw with throttle. The LSD allows for a slight wheelspin that is just faster than the forward direction of travel.

The open diff SE was just spinning it's inside tire on the corners with any power. And when one wheel does spin due to no traction, then you are either coasting, or you are spinning the car.

The LSD can be more tricky since if you lose traction, it happens to both wheels equally and sometimes suddenly.

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Whatever you do with the gearbox, always remember that the clutch is total crap. Higher ratio first gear will expose the inherent judder in the clutch and a chain is only as strong as the weakest link. I think that the twin plate clutch was probably designed on a Friday afternoon in 1923 and made out of left over cheese and bacon. All this said, the higher ratio close ratio 'box that GTO do is marvellous once the car is moving. Better shift, better acceleration through the gears and 500 bhp plus capability. (oh and an LSD) I have gone back to the standard box but mine still judders. Having lived with both for years, I would certainly go back to Kevin's 'box. I only wish they would do the same for the clutch as they did for the springs and dampers! One of the reasons that the taller ratio 'box was better was that you could put it in second at 15mph and then take it out beyond the legal limit without having to change gear!

And...What is more...My red vacuum hose from the wastegates fell off a few months ago. This meant that there was no boost control. There was no fuel cut out at any stage and so I presume that there wasn't a ridiculous amount of overboost, but the performance was stunning. It was the closest drive to a Murcielago I have experienced. Without the taller gearbox it would have been hopeless (and without the 1 piece shaft, probably broken as well!)

What do you suggest in place of the stock clutch?

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the clutch is an 'race type -or let's say 'sports-type' ...but the clutch shaft with those weak splines is not made for the effects of the non-damped engagement , as with those stiff plate-centres.

Edited by G

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What do you suggest in place of the stock clutch?

It needs redesigning or a suitable aftermarket replacement sourcing. Kevin at GTO has been nagging me to send one of my old dragging clutches and a flywheel to him so as he could possibly re-engineer it to reduce judder and failure rates. I have 3 flywheels and five clutches in my little transmission graveyard! I must get round to sending them as I am sure he would sell loads more gearboxes if the judder and fragility could be taken out of the crappy clutch....If only lotus would do for the clutch what they did for the suspension! I have often wondered what a change of material would do for the clutch (carbon maybe) There is a guy in the States called something like Butoni who does twin plate carbon clutches for Lamborghinis. I mean, there can't be a huge difference between a Countach and a V8 Esprit.

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Could your clutch issues be "driver behavior" related?

So called "warped" brake rotors are usually a symptom of driver behavior rather than materials or design.

I know of a Sport 350 owner who was complaining of clutch judder to another V8 owner (Johan). Johan took his car and performed a little clutch resurfacing (rebedding similar to brake bedding) where he burned off the old built up friction material, which was unevenly deposited due to driver behavior, and then re-deposited a new layer of friction material in an even layer... Issue solved.

I have fixed brake "warping" judder, caused by a panic stop, by following a re-bedding procedure. Clutches are basically the same as brakes.

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I have recently upgraded my UN1-027 gearbox as I have highly modified the engine and blew the 2nd gear syncro twice now,

Installed the Quaife replacement gear set, already had their limited slip diff installed previously

I did run into a little problem with this upgrade, I installed new syncro's yet again, just for the hell of it and got burned ... The syncros were aftermarket and seemed to work well going up the gears but would grind all the way back down, after pulling the gearbox out again and examining the syncros I found that the coating on the back of them was not the same as the Lotus ones, so I put my old ones back in and now everything is good again

Regarding the shudder effect pulling away from a standing start in 1st gear, I too felt this and it was not fun to experience, so I pulled the gearbox out again and replaced the flywheel and dual clutch, but the shudder was still there !!! :/

Next I replaced the gearbox mounts and added a new rubber coated washer to the passenger side mount as I noticed the gearbox does not sit completely flush on them, this cured 99% of the shudder, for me anyway

-Marcus

Edited by Marcus3

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I've driven an Esprit (89SE and 91 X180-R) with and without LSD on street and track (back to back) and I can tell you the LSD makes a big difference. So much so that I bought an LSD from GTO for my 89SE.

Travis.. Was that an ATB or ZF type diff you tested?

I am in the process of ordering a complete upgraded UN1 from GTO Racing and was discussing the ZF or ATB diff option. Each type seems to have its advantages and disadvantages. I was concerned that the ATB would go into open mode if one wheel broke ground, upsetting the car. The ZF on the other hand could create added understeer on power-on lock-up. If you can shed more light, that would be helpful.

Lee and Kevin at GTO seem like upstanding sorts to deal with. Any feedback on their product and service?

Edited by f1karting

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Travis.. Was that an ATB or ZF type diff you tested?

I am in the process of ordering a complete upgraded UN1 from GTO Racing and was discussing the ZF or ATB diff option. Each type seems to have its advantages and disadvantages. I was concerned that the ATB would go into open mode if one wheel broke ground, upsetting the car. The ZF on the other hand could create added understeer on power-on lock-up. If you can shed more light, that would be helpful.

Lee and Kevin at GTO seem like upstanding sorts to deal with. Any feedback on their product and service?

The X180-R uses a ZF limited slip differential. The Quaife is of course an ATB.

The ZF will be better for racing or super competitive track driving, but the Quaife will be 99% as good for all purposes except when one wheel is off the ground as you said. And it does seem to add some understeer. My car has almost none.

Kinda like my car here recently ;)

MK4_2976.JPG

The Quaife also acts primarily as an open diff at high speeds where no differential wheel speed is happening.

The ZF will act as a locked diff until friction makes it slip.

both feel great in the Esprit, and I would not go back to an open diff!

GTO was great to deal with even from overseas via email and the phone (though the Welsh are difficult to understand).

I paid via a bank transfer.

You can see my install here

http://picasaweb.google.com/lotusse/LotusQuaifeLSD#

I was able to seal the oil from leaking, just fine. Some complain that the Quaife is difficult to seal, since it does not have the o-ring grooves.

Edited by Vulcan Grey

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Awesome post!!!

A few questions from a noobey ;)

No LSD in the 2004 UN1?

Anybody upgraded to the 6sp GTO solution?

Does the stock 2 disc clutch handle 500hp (RW Hp)?

What point do the axles need to be upgraded (Hp)?

Would like to take the car to the 500 Hp figure it was intended to be...

Thanks!

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Hello,

To answer those questions:

- no, there is no LSD fitted as standard in any of the V8 variants

- there are a few on here: RobC has the GTO 6-speed (email: Rob Carrier)

- the stock AP twin plate is specified to handle 400Nm, but has been proven to handle over 450Nm.

Both GTO and AP can supply the 1" 23T friction plates.

- the next weakest link is the CWP in the gearbox. This is also rated to 400Nm, but has been proven to handle over 450Nm.

Running high engine outputs will run the risk of CWP failure.

There are plenty of chargecooled V8 projects on here to give you some ideas for increased power.

Good hunting

Cheers,

Mike S

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Mike replied to your PM - thx!

Then what starts breaking at 500hp?

I've got the following understood:

- Transmission

- Clutch

What about axles, motor mounts, wheel studs, etc.?

- Edited to keep on topic of thread.

Edited by FastZilla

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