Gearbox oil

[Kipster]

I would like to change my 126 gearbox oil. I have two haynes manuals, the older manual states use 80w/90 oil (not hypoid), but the more recent suppliment manual states that i should use multigrade engine oil 15w/40. My car is a 1973 aircooled but with a 650 engine fitted, so im guessing the gearbox is maybe circa 1973.

Thanks in advance.

Cliff

[Rusty's Uncle]

Hi Cliff, there has been a huge amount of debate about oils on this and other forums about the most suitable. I have also had chats with a couple of specialist oil suppliers and generaly end up with my head reeling 
Anyway in conversation with the "Guru" Smallcox recently he recomended Mobil 1 SHC 75w/90 as that is what he runs in his 5 speed gearbox driven by his turbo engine.
Just filled my gearbox with it last week.

[GTMaster]

I use an additive with 80w 90 transmission fluid. I've noticed that all 126 gearboxes produce a quiet whining noise in 4th gear (if it's very loud then the gearbox is probably broken). After pouring in the additive it ran much more quietly but since i have a small leak (apparently the additive stops leaks but it hasn't on my gearbox) it seeps away after a while....

http://www.wynns.eu/Product.aspx?p=59403&g=GRP_PRO_OIL

[Rusty's Uncle]

Funny you should say that because I have just fitted a gearbox that has done less than 8,000 miles and was told that it was perfect. It is in all respects except that it has a whine in 4th gear. 
Guess that it will not cure itself but sure as hell not going to take it out until at least next year. Only done about 65 miles on it so far, it's annoying but sure that it is not terminal. Then paid a visit to a guy on friday who has been messing with 500s for many years. I started telling him about the car and said that I had fitted the gearbox but..............
He finished the sentence " it has a whine on 4th gear"
How did you know that?
He said that he was just talking to a guy the night before who keeps getting the same problem.
Now I have run some 126 boxes in a shocking state but never come across this before.
I would say that if you have a good gearbox give it the best treatment you can 

[Kipster]

Thanks for the help.

Did a little research and found that 75w/90 is actually the same viscocity as 10w/40 engine oil. Weird!
Also hypoid oil will corrode certain parts of the gearbox if it is not recommended, (it is not for the 126).
Oh and my gearbox whines in first not fourth?

[Pete126]

I'm running Mobile One 15/40 fully synthetic in my 126 Gearbox and Engine and it does have a slight whine in 4th.

[KAL SPL]

I just replaced all the bearings in mine and run 80w/90 and it has no whine in 4th.

[compo1970]

20/50 classic oil. Ive ran it in mine for years now with no trouble or wines what so ever. just change it together with the engine. as long as you have the standard sump not a bigger alloy one, 1 gallon does the engine and box with additive in both.

[Amateb8]

What about this? This is the one specified in the handbook.

http://www.ebay.co.uk/itm/ZC90-Gearbox-Oil-Early-Fiat-models-Fiat-500-126-/110757360427?pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item19c9a7332b

[Fiat126Fan87]

I want to change the oil on my gearbox as well, mines a 89' BIS - can anyone recommend which oil I should use? Many Thanks

[ciaoflyer]

You can get the Tutela ZC90 from any Fiat dealer and it is suitable for the BIS!  

[Aaron]

As Rusty said, this one has generated quite a bit of debate in the past.    The first section on the referenced page (under the heading Translation) was interesting.

What I found was the following I reported in my Resoration thread:

As a further update, I've swapped the gearbox oil to 80W/90 spec.  I was finding after about 50 km of driving that the ability to shift out of gear was bleeding difficult with the 20W50.  A quite intense internet search finally convinced me that what I had in there was wrong, as I found a 126EL handbook and a 126P handbook both in polish on the web.  The former listed 80W/90.  The later Oliofiat zc90.  I've also had advice from separate sources in the east the manual states Tutela zc90 - looking that up listed it as 80W/90 oil.  The main clincher for me was this reference I found here in the US http://books.google.com/books?id=bAEAAAAAMBAJ&pg=PA35&lpg=PA35&dq=oliofiat+zc90&source=bl&ots=BUEi6QYPA7&sig=d6XVgb-iBepe1ihIai3IHNex0zQ&hl=en&ei=Yq1nS9ynBoGOkQXOysi5CQ&sa=X&oi=book_result&ct=result&resnum=1&ved=0CAkQ6AEwAA#v=onepage&q=&f=false.
upon changing the oil I found that the effectively 300 km old oil was black and there were a few specs of brass/bronze in the pan - however these could have just been stirred up by me actually driving the car.  I've put in Castrol EPX 80W/90 - mainly because I had this from my Lada days - which is both a hypoid oil and GL5 rated.  So far after 60 km of continuous driving the shifting is much improved - no longer baulks at changes.

[Da Londo]

Did a little research and found that 75w/90 is actually the same viscocity as 10w/40 engine oil. Weird!

Did some research on viscosities on the web and found that the above is quite normal because of the different grade systems for  engine and transmission oil. At this chart http://globalindustrialsolutions.net/viscosity-grade-chart.php you can see that the 10W and the 15W are in the same range as the 75W, and that 40, 50 and 60 are within the 90 range. So it all depends on temperature and overall oil quality, this quality is more impotant than the viscosity range. Looking at that chart one would think the 20W or 25W would be closer to 80W but these oils do not do well at -10 degrees or lower so I guess that 15W-40 multigrade mineral oil would be just fine for the gearbox.

[Da Londo]

Yesterday I was talking to my boss at work about gearbox oils as he ownes a vintage dirt bike and he wanted to change oils. The discussion started because we have automatic transmission fluid Mobil ATF 220 for the telehandlers and they are apparently filled up with Mobil 424 when maintenance requires it. We then went to check viscosities ourselves and found out that ATF 220 is recommended for pre '94 cars. For more info on this: http://www.mobil.com/UK-English-LCW/heavydutyoils_products_power-steering_mobil-atf-220.aspx. I don't know the prize of this fluid but I do know one vintage Fiat and on vintage dirt bike that will be filled up with in the near future.

Features                                           Advantages and Potential Benefits

Good thermal and oxidation stability   Resists lacquer, sludge and deposit formation to keeps transmissions clean for
                                                        efficient operation over the fill life
Good anti-wear properties                   Meets the wear requirement to promote longer transmission life
Excellent low-temperature fluidity        Assist in improved start-up and clean fast lubrication at low ambient temperatures
Effective foam control properties          Smooth and lasting shift feel and reduced fluid loss in severe service operating
                                                        conditions
Compatible with all common seal
materials used in Type IID
transmissions                                   Maintains effective leakage control

Mobil ATF 220   
Viscosity, ASTM D 445   
cSt @ 40°C   37
cSt @ 100°C   7.0
Brookfield Viscosity, ASTM D 5293   
-cP @ -40°C   33,000
Viscosity Index, ASTM D 2270   153
Pour Point, °C, ASTM D 97   -44
Flash Point, °C, ASTM D 92   200
Density @15°C, kg/l, ASTM D 4052 0.870   0.870
Colour   Red