General What is going on with CVs?

[Triatium]

Hey there guys

IT sounds like either my cv boots or joints are going AGAIN. Getting bad clunking sporadically during turns, and such.

How long are cv boots / joints supposed to last? If I recall correctly, think I've replaced the boots at least twice within two years. It's getting bloody annoying. What could cause the cvs to act up?

I haven't taken a look to verify that it is indeed the boots, but the clunking etc. is exactly like it was before, so assuming (think it's a safe bet though).

Also, where would one put gearbox oil in on an Uno 1100 Fire? I don't know, and people keep telling me that it's not necessary. However, my gearbox has dropped a bearing, and, whilst still running (ok, needs to be reconn'd, dropping out of 5th gear etc) wondering if the numerous problems are being exacerbated by lack of lube?

Regards
Triatium

 

[randomspeedfreak]

if you dont have the plastic boot on the CV joint it will get buggered up very quicky.
im sure you have put these on, just checking incase.

 

[alexGS]

For clunking, check that the driveshaft nuts are tight. They both have a right-hand (normal) thread, so the one on the driver's side sometimes works loose. On certain larger FWD cars and the Uno Turbo, the CV joint is held together by a ring of hex-socket bolts that sometimes work loose, but I don't think your Uno FIRE uses these.

Some replacement CV joints are poor quality, though I don't have anything factual to back up that remark; however, it applies to balljoints as well which I have definitely found to last worse than the originals. So it is conceivable that the new CV joints have worn out - you're right-hand-drive, so I would expect the left joint to wear out first (from U-turns to the right!). Or, perhaps only one joint was replaced and now the other one needs doing...?

Also, CV joints MUST have the correct molybdenum disulphide grease. New grease is usually dark grey and pasty, old grease is dark green and more liquid. Usually you can get enough life out of the original CV joint just by cleaning and repacking with new grease. Inspect the central 'spider' and the outer cage carefully for cracks. I have some broken 'souvenirs' in my garage

As for gearbox oil - I'm with you on this one - I always change gearbox oil, as it's relatively cheap, sometimes makes a big improvement to the gearchange, and lots of microscopic metal tends to drain out with it, which can't do the gearbox much good if left. You need a non-EP oil for the Uno gearbox. 'EP' stands for 'Extreme Pressure' and refers to sulphurous-phosphorous additives that give normal gear oil its horrid smell. Those additives are not necessary for a front-wheel-drive gearbox (which has no hypoid bevel gears) and the additives are thought to eat away bearings and synchroniser surfaces in a way similar to acidic attack.

The correct FIAT oil is sold in blue 1L bottles marked 'Tutela ZC90', but a good alternative seems to be Castrol VMX ("for five-speed manual transmissions"). Either of these does not have the EP additives, so it looks and smells like engine oil (i.e. no smell).

In a pinch, you can use budget engine oil (20W40 or 20W50) in the gearbox. Engine oil viscosity numbers are different to gear oil viscosity numbers, so a 50-weight engine oil is about the same as a 90-weight gear oil. The only thing is that the engine oil lacks certain 'friction modifiers' that improve the action of the synchromesh. But it's a lot better to use engine oil than to have no oil in there.

Though some manual transmissions use ATF (automatic transmission fluid), I don't recommend that - it's too thin, tends to accentuate noise and bearing wear.

And finally to answer your question - on the front of the gearbox, you'll see a 12-mm hex-socket plug, which you need a 12mm Allen key to undo. That's assuming that there hasn't been a substitution of a 17mm hex-head plug, in which case you just need a 17mm spanner. There is a similar plug under the left-hand driveshaft, which is the drain point.

Do not be confused by a plastic plug somewhere on the top of the gearbox - that's the breather. The fill point is always a metal plug on the front. Fill up to overflowing, which will be around 3L for the early-style gearbox (gearchange linkage by two rods under car), and only a little over 1L for the newer-style (FIRE only) gearbox (rod and cable gearchange linkage, push down to select reverse).

-Alex