UN1 Improvements

[Stephane Goria]

Gentlemen,

Some time ago, I announced I was engineering ways to improve the UN1.

The first target was to work on the differential fitted in the R25-UN1 and R21 Turbo-UN1. These gearboxes that are commonly in use in our replicas suffer from a weak differential...(not the only weak point...but solutions come out..;-))

As you may know, the differential is made of only 2 pinions and it is obviously too light to handle the torque we apply on it. It is already a problem of security...Think about driving at high speed with a wheel that suddenly block because of a broken differential. A pair of pinion gears is adequate in many instances for driving of the vehicle. In heavy-duty drive, however, a four pinion gear differential is more satisfactory since it will transmit greater torque with less strain on the differential

So my first target was to build a kit making our weak 2 pinions differential into a heavy duty one with 4 pinions.

After many tries and a lot of time over CNC machines, I get out with an easy kit allowing this considering my main focus to keep these mods as cheap as possible.

Pic 1 is a view of our comon 2 pinions differential.
Pic 2 is a view of our upgrade kit allowing to fit 4 pinions.
Pic 3 is a view of the kit installed in a differential (R25) with an electronic sensor.
Pic 4 is a view of the kit installed in a differential (R21) with a mechanical sensor (UN1-13)

I'll continue to post the other mods engineered (mainly to ehance the primeshaft) in a few time (waiting for some CNC prototypes and testing).

Cheers

Stephane

[Simon]

Stephane,
That looks good
Simon

[Stephane Goria]

Thanks Simon.

Stephane

[Ian Anderson]

Hi Stephane

I have a UN1 bax with a tag 09.
I was told by someone that this was an Alpine Rally box that came with 4 spider gears.

Perhaps you could confirm if this is the correct box designation as I have never been able to find an 09 mentioned in any literature

I have not had the box apart so cannot advise if this is correct but perhaps the parts may already be available

Ian

[Dave Bilyk]

Ian,
although yours seems clearly to be a UN1, if you look at the UN5 differential exploded view (in the UN gearbox manual) it shows a 4 pinion diff similar to Stephanes design. So assuming that this diff would fit in a UN1, a 4 pinion diff as standard was possible.
I think the UN5 was used in the Renault Master van, hence maybe the need for a stronger diff.

Dave

[Stephane Goria]

Ian,

You are right UN1-09 officially doesn't exist in Renault litterature. I guess you might be right with the rallye purpose. This is clearly a hand built gearbox as the serial sticker is not in conformity with the renault quality standards : Serial must be 6 digits and filled with 0, so your would be 000014 and it is not. Also the low serial number I can see (14) makes me feel about special productions.

Obviously the best way to know would be to open it but we can already try to understand better your gearbox by few hints.

Look at the casting years stamped in every part of the housing? (this will allow us to know what era to look for)?

Look also at the casting revision on the housings (might be 1, 2.2, 1.4, 4..)?

Look at the transversal bolts, the 2 bolts that come across the gearbox located near the speedometer sensor (mechanical). Are they 10mm or 12mm size (12mm were not available to public and only reserved for racing department)? Obviously after many years they might have been removed and exchnaged to the standard 10 mm ones.

Regarding the differentials, all differentials fitted in Lotus, Venturi and Alpine were 4 pinions ones. Only the R25,R21 and Espace 2 differentials were supplied with 2 pinions.

The UN5 (MAster Traffic gearbox) is already a 4 pinions differential. Unfortunately this gearbox is not suitable for our use, with a final ratio of 7x41 you have a lot of torque but no speed unless your engine can attain 9000/10000 rpm....;-)

Unfortunately I have to stop this thread. The forum moderator informed me that I can't do any announcments without having a regular vendor status. The rules have to be respected.

I will obviously continue to try to bring help to everybody with questions on UN1 gearboxes.

Cheers

Stephane

[Stephane Goria]

Ian, just to be complete as there might be an easy answer. UN1-09 is not a renault gearbox but UN1-S-09 is the common code for replacement gearbox UN1-04 & UN1-08.

Just in case you can see an "S" in your serial.

Cheers

Stephane

[Ian Anderson]

Thanks Stephane

I'll have a look around ans see if I can get any more serial numbers

Regards
Ian

[Kevin Box]

Stephane

Can post the following information of PM it to me

1 Bearing part numbers that are not renault parts (SKF or similar)
2 Bearing part numbers that are only available from Renault
3 Gasket and seal kit part numbers


Also I have a UN1-13 and want a 4 spider dif for it.
I hear there is a Renault 4 spider centre that fits straight into the UN1-13.
Can you tell me what it is from and what is involved in fitting it.
The transaxle is apart at the moment
Is it possible to fit extra spiders into the 2 spider case ????

thanks

Kevin B

[Stephane Goria]

Hello,

sorry didn't see your message first.

Bearings : the only standard one is the differential one wich is standard ref 30209 available from all manufacturers. These are the differential bearings available from any manufacturer.

The others are Renault specific as per the gaskets, so you need to check this with your local renault dealer.

4 spiders diff : The UN1-13 has a mechanical speedo sensor and so a specific crown groove on the diff housing. Beside the UN1-13, there is just an other Renault gearbox with a mechanical speedo sensor , the one from the renault espace V6 un1-021. Unfortunately both of them have 2 spiders only.

I have UN1-13 diffs specifically machined to handle 4 spiders if you want.

Cheers

Stephane

PS : all UN1/UN5 parts are now available in the USA (colorado)

[Eddie]

Stephane,
Did you ever get a 1 piece shaft made up or is it just as easy to get one from GTO.
Cheers Eddie.

[Stephane Goria]

Hello Eddie,

At the moment no 1 piece primeshaft and so I think GTO is certainly one of the few reliable and serious company to deal with this.

Basic problem is the cost of the helicoidal machining as unfortunately the pinions sizes (too close to the shaft diameter) do not allow to have a naked shaft and then to add pinions (wich would drastically reduce the cost of making them).

Anyway, what are your engine specs? because there are less expensive ways to ehance the strength of the UN1 without changing the whole shaft but obviously staying into a reasonable Torque/HP/Rpms use..

Greetings from France with a sunny day...

Stephane

[Eddie]

Stephane,
The engine is a special....engine no.2 of the 3 origonal Renault bi-turbo,s sent to Hartage for tuning by Renault...rumor has it.. it,s the only one left, as the others 1 & 3 blew up on the dyno...I have the papers from Hartage...have you any info on the engines...installed MID-ENGINE in a Renault Alpine..all converted by myself..400hp.standard... chiped & tuned to 600hp...so you see the need for a strengthed gearbox...this is what I get up to now I,m retired.
Cheers Eddie.

[Stephane Goria]

Hello Eddie,

Thanks for the info.

No sorry no information at all about these engines. It makes me curious what is the base engine : the standard 6 cyl PRV? Waht mods they made : guess something more sophisticated that just increase turbo pressure..?

For the actual UN1 configuration and with a not too heavy vehicle (the lotus V8 suffers from weight) you can go up to an average safe 40 mkg.

Above this with few ehancements 50-55 mkg are reachable too but you are in the tensile strenght limit of the primeshaft material.

So and as you know, it's always the same question : how do you intend to drive the car...;-) : weight of the car, cx, tyres, torque ranging, rpms..etc...Configuring or just selecting the right gearbox involves many parameters.

To summarize : up to 40 mkg normally the standard UN1 is more or less ok, above you need some ehancements but the standard primeshaft is still ok up to 50-55 Mkg, above this better to change the primeshaft if you intend to drive hard.

[Eddie]

Stephane,
The engine ..I think.. is roughly based on the Alpine 610 12vl. 3ltr. V6...using differant pistons etc. & 2 kkk turbo,s designated Z7XL. It,s a version of the Saffrane bi-turbo. My other Alpine has a XM 24vl. with 6 Toyota throttle bodies.
The car is just an exercise to keep me busy & stop me getting bored...but it will get a run at a track here in Holland ..you know ...what can she do Mr.
Hopefully my next project will be a GT40..but using the parts i,ve developed for the Alpines...rose jointed suspension etc. etc.
Cheers Eddie.