TO change or not to change the gearbox lubricant?

[nicky4tl]

Hello all,
Antoinette (1983 R4 tl bizarrely unrusty) has just passed ner 85000 mile. The manual as I recall mentioned changing the gearbox lubricant at 60000 i think. We've had her since 50000 and never changed it. A mechanic told us to leave well enough alone and that changing the oil might create problems. He said there was enough oil in there but that it was rather grey.
So does anyone have any recommendations for me? I dont like the idea of driving around with a grey paste of metal particles for lubricant but really havent a clue about these things.
One other thing. Antoinette has no rust in her chassis, suspension mountings or floor. Ive changed two front wings and a door and one rear panel is pretty holy but nothing structural. Is there anything i should do to keep her chassis safe seeing as shes made it this far?
Thanks in advance.
Nicky

 

[La Poste]

I used to change the gearbox oil on my R4 fairly regularly (I can't remember exactly how often, but think it may have been every 20,000 miles), and the gearchange was always much nicer afterwards. Changing it regularly certainly didn't seem to do any harm, and personally I'd rather have nice fresh oil in there than all those metal particles! My current R4 falls into the long-term non-runner category, so obviously I don't change its gearbox oil, but I religiously change my 2cv's gearbox oil every 10,000 miles (as the manual suggests), and it doesn't seem to have done that any harm (quite the opposite in fact, as it's still going strong after several million light-years).

Regarding conservation of your chassis, the best method would be to store the car in a cool, dark, well-ventilated room, with very low (and constant) ambient humidity - I know what I'm talking about here, as I used to work for a motor museum! Unfortunately, although storing your car in such conditions will ensure the longevity of its chassis, it also means you won't be able to drive it, which is a bit of a disadvantage.... :?

As a more practical alternative, you should cover anything that might rust with something which will prevent it - my favourite is Waxoyl mixed with gearbox oil (another reason to change it!). Waxoyl is designed to prevent rust, but despite what it says on the tin tends to dry out and crack (which means water can reach the metal it's supposed to be protecting) - by mixing it with oil it stays nice and runny, and seeps into all the nooks and crannies which might otherwise get missed. Old engine oil mixed with Waxoyl seems to be okay too, although there is a school of thought that says the acid present in the oil as a result of the combustion process will corrode the metal (it's never done any of my cars any harm though...). Thinning Waxoyl with white spirit (as it suggests on the tin) isn't much use, as it will still dry out and crack.

Once you've got a nice sloppy cocktail find someone with a compressor who can inject it at high pressure into every box-section you can find, as well as underneath of course. Doing it on a hot day will make the mixture more fluid, which is good. Make sure any drain holes in the chassis are clear afterwards (otherwise water can get trapped inside), and that any old loose or flaking underseal is removed first (as this forms a perfect rust-trap). Once you've done it make sure you repeat the process at least once a year, and that you regularly hose off any accumulated mud and salt in between. Finally , have a supply of sawdust or sand available for a few days afterwards, as the car will dribble disgusting oily stuff on your driveway as the excess Waxoyl drains out of the chassis.

I seem to have written an essay on the subject - hope it's useful!

 

[angel]

50.000miles seems a long interval. Change it, this gray color doesn't seem good to me, probably mixed with water??? Anyway, since gear oil is cheap, don't risk, change it. Make sure that the oil will be suitable for hypoid gearing, not just "gear oil", as it has to lubricate the final drive as well.

 

[malcolm]

I like the idea of mixing waxoyl with oil. I think I might give that a try. Have you hit upon an ideal ratio of waxoyl to oil? I wonder if welding fires might become more of an issue. Maybe I should do some fire tests.

Some years ago I invested in a waxoyl injecting gun for a compressor. It's wonderful. The waxoyl is sprayed in at 90psi (from memory) and covers the chassis really well. I tend to leave the waxoyl in in a bucket of hot water for a few hours to thin it rather than mixing with white spirit.

There are a few Renault 4 specific things you could do. It helps to hose the mud from the rear outer suspension mountings regularly. Also there is often a gap between the top of the suspension mounting and the body that collects mud and causes the rear of the sill to rust from above. It's a good idea to clean that out then seal it or spray lots of waxoyl down it. I slao drill drainholes in the bottom of any chassis member that doesn't already have drain holes. You can use the new holes to squirt waxoyl in.

 

[nicky4tl]

Great, thanks for the advice. Ill change the oil as soon as i get a chance. Can anyone recommend a brand or will i just ask for gearbox oil suitable for hypoid gearing?
thanks again

 

[Enrique]

I change Gearbox Oil every 25000km. I always use Shell Spirax 80. I sold the old gearbox which had been treated this way and it was as good as new, after 20 years of service, so I think the oil change didn't hurt it much... the new owner just cleaned and mounted it.
About the chassis, just like LaPoste just said, after we reinforced the chasis, we drilled a few small holes in the hollow boxes in the front floor and in other internally unreachable places. We then shot some similar mixture (here it's sold as anti-rust-something) into those holes, first with the back (very) lifted, then with the front, for the excess mixture to flow into those spots you can't reach no matter the pressure you apply. It took quite a while for the car to stop leaking excess mixture applied... :?
Our climate here is very friendly to metal and we don't have the salt problem you guys have over there, but we intend to repeat the process yearly.
These frames rust from the inside, so when you see the damage, in most cases it's too late...
Another tip: You can glue a small magnet to the tip of the bottom screw of the gearbox (as many cars already have). This will hold many metal particles between oil changes, so they dont go back into the gears with the oil. Just be sure the magnet is very well attached, or you may have the opposite result!

 

[Chris H]

theres already a magent in the box, its just not on the drain plug, its wounted bewteen the 2 halves of the casing, its donut shaped, can't get to it unless you pull the box apart.

 

[Duncan]

How can changing the gearbox oil cause probems ? you are more likely to get problems running it with a grey sludge. I cannot belive a mechanic would say something like that !