Gearbox oil

[maigret]

I would like to top up the oil in my gearbox or even treat it to new oil.

There appears to be a plug on the top under the rubber bung in the boot space and two drain plugs underneath. Is there a level plug on the side? Or do you put a measured amount in the box.

ps It's an s2 Citroen box

[lotusespritworld]

For the Renault box you just fill it up until it start to come out of the side fill plug. Not sure about the citroen box.

Heard it's a bit of a pain to change/check. Going to do a guide in the future for LEW.

kato
Lotus Esprit World

[maigret]

Yes. That is how I have usually topped up boxes. However there is no obvious level plug on this one.

[lotusguy]

maigret said:

I would like to top up the oil in my gearbox or even treat it to new oil. There appears to be a plug on the top under the rubber bung in the boot space and two drain plugs underneath. Is there a level plug on the side? Or do you put a measured amount in the box. ps It's an s2 Citroen box

Graeme,

You have the early Cirtroen box. It differs from the later C-35 Citroen box. One of these differences is that it has two drain plugs. One for the main box and another for the 5th gear extention housing. The box was originally designed as a four speed. Citroen decided to uprate it to 5 forward gears by merely adding the 5th gear in a housing 'tacked' on the rear (Gotta love the French!).

The fill plug is on top, accessible through a rubber plug in the trunk under the carpet. You will see two 13mm plugs on the left hand side of the gearbox. One of these is the fill-check plug and one the blanking plug. You do not want to remove the blanking plug. The fill-check is usually marked w/ yellow paint, but yours may have worn off. In either event, it is the 'lower' of the two plugs.

First open the fill plug, then with the car on very level grouhd and a catch pan with a 3 ltr. capacity underneath, open each of the drain plugs. Allow at least 10 minutes for all the gear oil to drain out, if not, you will overfill the box.

Once drained, refit the drain plugs and add ½ or 1.0ltr. of the total capacity of the proper fluid (2.25 ltr. SAE 80/API GL-5 non-hypoid gear oil). Then remove the fill-check plug and slowly add the remainder of the fluid. I say slowly because the gear oil can only enter the 5th gear housing through the spaces between the ball bearings in the roller bearing which supports the 5th gear shaft, it takes time for this to occur. If you add too much too soon, it will back up in the main box and leak out the fill-check hole making you think it is filled.

Many Esprit owners are unaware of this and are actually driving with a low oil level in their gearboxes.

As you approach the 2.25 ltr. point, you will see some leakage from the fill-check hole, once this happens, refit the fill-check plug and fill plug on top. If you have leakage before most of the 2.25lts has been added, either you haven't properly drained the box, of have allowed insufficient time for the gear oil to migrate past the roller bearing described above.

Having said all that, you could just add the appropriate 2.25 ltrs. of fluid, but run the risk of overfilling, so I do not recommend this approach. Overfilling will cause the gear oil to foam which effectively creates an oil starvation condition which will damage the gears. Happy Motoring! Jim'85TE

[southenddc]

Excellent advice, i followed it recently when i did my oil change..ever since the box has been a lot quieter and smoother, i also had a leak so it was probably really low. Advice like this saves you £££'s. Maybe Kato could use this info on the site somewhere??

Cheers

Brett 86 S3

[Lasse]

Hi Jim!

Is it the same problem with the oil entering into the fifth gear extension also on the later Citroen boxes (C35)?
Good description indeed...

Thanks /Lasse


>> Edited by Lasse on Thursday 6th November 14:15

[lotusguy]

Lasse said:

Hi Jim! Is it the same problem with the oil enetering into the fifth gear extension also on the later Citroen boxes (C35)? Good description indeed... Thanks /Lasse

Lasse,

The procedure is the same with the C-35 box with the exception that in this newer C-35 box, the drain plug on the 5th gear casting/housing was eliminated.

This means that draining the fluid is even more important as without the extra drain plug, the fluid must also migrate back out of the extention casting/housing through the ball bearings of the 5th gear shaft into the main box before it can be drained. A really poor design actually.

Because of this single drain plug on the C-35 box, it is beneficial to slightly raise or tilt the box forward (say 3°-5°) with the drain plug removed, to ensure that this extention housing has been fully drained. Then, return the car to level so the fluid can drain out the drain hole in the main box.

Again, upon refilling, time must be allowed for the new fluid to fill the extention housing. Failure to do so will result in underfilling the box. Happy Motoring! Jim'85TE

[maigret]

Thanks Jim

I'll check it in the morning.


Graeme

[marcvv]

Oops, my specialist gave me a jerrycan with 3 liters of hypoid oil for my 84TE; and I have recently replaced the old oil with this oil(2.25 liters exact); what's the diff between hypoid/non-hypoid ?

regards,

Marc

[lotusguy]

marcvv said:

Oops, my specialist gave me a jerrycan with 3 liters of hypoid oil for my 84TE; and I have recently replaced the old oil with this oil(2.25 liters exact); what's the diff between hypoid/non-hypoid ? regards, Marc

Marc,

The difference has more to do with the gears than the oil. When speaking about transmissions, there are basically two types of gears, hypoid and straight- cut gears. Straight-cut are the simplest and easiest to cut while hypoid gears posess a more complex tooth shape. Hypoid gears appear to be twisted.

Straight-cut gears are usually stronger, but much noisier. Hypoid gears tend to be much more quiet. Another advantage, especially in differentials, is that unlike straight-cut gears, which engage the pinion shaft and crownwheel on it's central axis, a hypoid gear can be designed to engage the crownwheel below the axis of the crownwheel. As the height of the crownwheel is essentially fixed by the height of the wheels, a propshaft using hypoid gears can be lowered with respect to the chassis and thus produce a lower center of gravity resulting in better handling.These are fairly universal in all differentials.

Because of the sliding contact made by hypoid gears, their hydrodynamic contact pressure is much higher. Standard gear oils will not stand up to these extreme pressures. The oil will be forced out from between the contact points (remember, there should be no metal to metal contact between the gears, rather a miniscule coating of oil exists between the gears). In order to accomplish this, considering the increased pressures, gear oil manufacturers modify the oil through the addition of increased sulphurs and other additives to withstand these increased pressures. These oils are referred to as EP (Extreme Pressure) orHypoid oils.

But, the addition of these chemicals also increases the corrosion potential to soft metal parts such as synchros accelerating their wear.

The Esprit box contains both the gearbox and differential, it is a transaxel rather than a transmission. As such, it contains both hypoid gears and soft metal parts and synchros. So, any gear lube chosen will be a compromise between what is best for both. Lotus/Citroen has decided that a Hypoid gear lube is more damaging than a standard gear lube.

Having said that, both lubes will work fine, but you will see accelerated wear of the soft metal parts using an EP or Hypoid gear lube. Hope this helps. Happy Motoring! Jim'85TE

[Dr.Hess]

Just to add to the mix, I recently changed my gearbox (Renault) oil. What came out was very clean, had about 15K miles on it, and smelled like "gear oil," that is, the regular stuff from the auto parts store. 2nd gear was a little sensitive on hot quick shifts. I replaced it with the recommended Mobil stuff purchased at a local Graingers and it is shifting better now.

Dr.Hess

[kjmorris]

I also have a problem with gearboxes, sorry to hijack the thread but I am desperate. The parts I want are the First/Second gear Synchroniser assembly and the two Synchro Rings that go with it, the rings are identical for both gears.
The Gearbox itself is basically a Renault 25 unit but the ratios are different. The box is also used on the Renault Alpine and GTA and the Lotus variant was done in conjunction with Alpine of Dieppe (Renault specialist car division). The gear ratios are special for the Esprit and is not in common with anything Renault, however things like Synchro Hubs and rings are common. I have rung some Renault parts departments but identifying the exact gearbox base unit is proving a problem. I tell them that "it's a UN1 16 gearbox" and they say "there is no UN1 16, there is a UN1 15?" "what car is it out of??"

[Del-Esprit]

I would check for a small metal plate on the gearbox that has the gearbox code on it, this is usually held on by one of the gearbox bolts. Unfortunaetly they often get left off when gearbox is rebuilt.

What car is gearbox from ?
I believe the code for the standard S4s gaerbox is UN1-026 and the V8's use a UN1-027. There is a UN1-028 but not sure which version possibly GT3.
The bearing sizes and locations are similar on all of the boxes only the ratios and final drive seems to be different.

I am currently using a Renault 21 Turbo gearbox complete on my car UN1-013. Just changed bell housing, gear selector casing and a couple of minor mods.
On inspecting the S4s gearbox and comparing to various other renault boxes I couldn't find any other synchro's or cogs that where a match.
I would suggest that the Lotus sourced parts are the only option if looking for repacements.

Derrick
95 S4s (R21T gearbox)
www.messaging.co.uk/del/lotus.htm

>> Edited by Del-Esprit on Wednesday 12th November 15:25

[JohnWatkins]

Here's a page listing technical data including ratios, so you can see which box had similar ratios to yours.
www.gt40club.clara.net/technics.htm

Here's the R21 Turbo owner's page, if you go to forum then sales & wants there's normally a few boxes for sale.
www.renault21turbo.com

Cheers,

John W
'95 S4s