what oil to use in the 850 transaxle?

[RobM]

The 850 transaxle has the unusual dual requirement of "safe for yellow metal synchro rings" AND "for use in hypoid differentials". I used to use Liqui-Moly GL4 (bottle said it was safe for both conditions), but they no longer offer it. Red Line doesn't have a solution. Motul offers Gear 300 Racing, but it's pricey at $28/liter. What are you using? Thanks.

 

[dnudelman]

Apparently $57.99 a gallon at Amazon. Quarts at NAPA

 

[ramona300]

I used Redline MTL in my box and I can assure you it's not suitable! Any GL4 oil made for hypoid gears should do the job. GL4 apparently is not as slippery as GL5 and is better for the syncros from what I can gather. I have some to go in my box when it returns from the shop. I can't remember what brand it is. I think it's a 90-140 grade.

 

[Jeff Stich]

The 850 transaxle has the unusual dual requirement of "safe for yellow metal synchro rings" AND "for use in hypoid differentials".

The 850 transaxle doesn't have yellow-metal synchro rings.

Here's a thread from a few years back about 850 trans lube:

https://xwebforums.com/forum/index.php?threads/850-transaxle-fluid.27108/#post-226146

 

[NM850]

I used Redline MTL in my box and I can assure you it's not suitable! Any GL4 oil made for hypoid gears should do the job. GL4 apparently is not as slippery as GL5 and is better for the syncros from what I can gather. I have some to go in my box when it returns from the shop. I can't remember what brand it is. I think it's a 90-140 grade.

You can ask Redline what they recommend for anything. They specifically advised against MTL when I asked.

 

[Dave Bassett]

Guys here recommended Redline MTL to me and the head mechanic at a local hot rod shop agreed,although he suggestedit mihgt be excessive when balancing cost and application. However,he put it in and, two years later, it has resulted in a dramatic improvement in function. Before, it would not downshift into second without grinding unless I double-clutched and downshifting to first while rolling always resulted in grinding. In addition, reverse could not be found! Now I can downshift (carefully) into second and even first without double clutching and reverse is relatively easy to engage. Just my experience, for what it's worth.

 

[fiatfactory]

The trouble is that MTL is a non EP oil, and the 850 differential being a hypoid gear configuration requires an oil with EP additives.

Factory manual says Fiat W 90M (SAE 90 EP)

A non EP oil in an EP application I would expect to see discolouration of the oil. The EP additive prevents the oil molecules "crushing" (microscopically) at the point of tooth mesh of the differential. While this may not cause the entire volume of the oil to become too hot, at a very localised level on the tooth contact face, the oil will be hitting 100's of degrees in temperature and over time would discolour.

SteveC

 

[DSpieg]

Darn, I've been using Redline MTL for the past 10+ years, guess I'll have to change it now

 

[ramona300]

Guys here recommended Redline MTL to me and the head mechanic at a local hot rod shop agreed,although he suggestedit mihgt be excessive when balancing cost and application. However,he put it in and, two years later, it has resulted in a dramatic improvement in function. Before, it would not downshift into second without grinding unless I double-clutched and downshifting to first while rolling always resulted in grinding. In addition, reverse could not be found! Now I can downshift (carefully) into second and even first without double clutching and reverse is relatively easy to engage. Justmy experience, for what it's worth.

This is what Redline MTL does to Pinion gears!

 

[fiatfactory]

This is what Redline MTL does to Pinion gears!View attachment 73669

That's a little unfair to just one manufacturer of oils... it should be something more like....

This is what an NON EP oil in an application that requires EP additives will do - it's the pinion contact face in the hypoid configuration of final drive gears that requires the EP additives.

Extreme pressure additive - Wikipedia

en.wikipedia.org

Spiral bevel gear - Wikipedia

en.wikipedia.org

SteveC

 

[RobM]

Thanks for all the replies. I see the answer is not so simple, and there is a lot of confusing input. Matt Brannon at MWB (who should know a thing or two about old Fiats) gave me the confusing answer to use NAPA GL-1 mineral oil, and to "...stay away from anything with EP modifiers as that will work against the sintered coating on the synchros." Huh? The Fiat 850 owner's manual specifically states to use SAE 90 EP.

Thanks for the correction about the 850's syncros!

A possible solution may be Motul's 90PA GL-4/GL-5 mineral oil "for all types of hypoid differentials". Motul also has a modern synthetic called Gear 300LS 75W-90, for "all hypoid differentials and synchronized or non-synchronized gears". Expensive and in limited supply.

JohnT from March 2015 (see Jeff Stitch's link above) suggested CRC's Sta-Lube 85W90 GL-4 hypoid oil, also available at NAPA. This seems like the best all-around product for the 850 transaxle.

 

[RobM]

Maybe now we've gotten to the bottom line?...Matt Brannon explains further:

The 850 based transaxle in your OTAS uses Porsche type sintered metallic round rings and steel sliding sleeves. The 128 and X1/9 trans, while packaged differently uses the same exact sliding sleeves and synchros, without an ounce of “brass” to be found anywhere in the trans, just like yours. Let me repeat, the same exact synchro rings and sliding sleeves are used in all three cars’ gearboxes.

Despite the owners manuals for 850s calling for an 90 WT EP modifier, this recommendation was halted in 1972-on for the 128, X1/9, and even all of the 124 transmissions. See attached owner’s manual recommendations for 1972 128.

I and Jon Logan at Midwest-124 only use 90 Wt Mineral Oil GL-1 (Factory recommended for 128, X1/9 and 124) or Redline MT90 GL-4 or Redline MTL GL-4 (closest synthetic to the original GL-1).

`````````````````````
So there you have it.

 

[dnudelman]

As I posted at the top of thread, Staylube from napa as Jeff Stich says. I got that off this board. The formulation now is gl5- not gl4. In any case, unless you're Ramona with a rebuilt box, any synthetic would just end up dripping on the floor. Since most of us put less that 1000 miles a year on an 850, I'm pretty satisfied that the sta-lube is the best choice per $

 

[fiatfactory]

Maybe now we've gotten to the bottom line?...Matt Brannon explains further:

The 850 based transaxle in your OTAS uses Porsche type sintered metallic round rings and steel sliding sleeves. The 128 and X1/9 trans, while packaged differently uses the same exact sliding sleeves and synchros, without an ounce of “brass” to be found anywhere in the trans, just like yours. Let me repeat, the same exact synchro rings and sliding sleeves are used in all three cars’ gearboxes.

Despite the owners manuals for 850s calling for an 90 WT EP modifier, this recommendation was halted in 1972-on for the 128, X1/9, and even all of the 124 transmissions. See attached owner’s manual recommendations for 1972 128.

I and Jon Logan at Midwest-124 only use 90 Wt Mineral Oil GL-1 (Factory recommended for 128, X1/9 and 124) or Redline MT90 GL-4 or Redline MTL GL-4 (closest synthetic to the original GL-1).

`````````````````````
So there you have it.

Sorry, but that is incorrect.

The requirement for an EP additive is not to do with the synchro operation, it is for the hypoid configuration of the differential gears.

Hypoid means that the pinion gear is not at the crown wheels centreline, in an 850's case it is offset downwards. This configuration (as mentioned earlier) loads the oil (being "crushed"), this is what the EP is needed for.

A 128 and X19 transmission is a NON hypoid drive, the gears are not at right angles to each other, and the pinion gear is at the crown wheels centreline.

it's comparing an apple to an orange.

SteveC

 

[fiatfactory]

as far as EP additives attacking the coating on the sintered steel synchro rings, I've only ever seen that once in many transmissions I've overhauled... and the first thing to remember is all EP additives are not the same. The only time I saw the "green death" on X19/128 synchros was on a trans that had been sitting around for some time, Ive pulled down transmissions that obviously had EP oil in it (it stinks - you CAN;T miss it) and no sign of green death.

To me it must have been the EP additive breaking down and oxidising, or combining with moisture to form yet another compound, which then attacks the metal, remember we are not talking yellow metals here, thats a totally different story.

A lot of EP additives are Sulphur (or Sulfur for those in the US) based compounds, oxidise them and add some H2O and there a good chance your going to get something aciidic in the process... IMO that's what causes the green death on the sintered metal synchro rings as used in a 128 / X19

The coating on that type of synchro is molybdenum, certainly is on Alfa Romeos, and I have some packets of Goetze synchro rings for Fiats that appear to have the exact same type of coating, and even have "Mo" in the part number.

Frictional properties and wear of a molybdenum coating and a bronze (Cu-10%Sn) with friction modifier fillers

A new manufacturing process and a new family of composite materials (bronze matrix + friction modifiers) for lubricated tribological systems, such as …

www.sciencedirect.com

SteveC

 

[fiatfactory]

IMO the reason why EP oil in a 128 / X19 trans is a no-no is that it froths and foams... the one and only time I put EP oil into my 128 trans after rebuilding the trans (back when I was 16 or 17 years old) I took the car for a spirited drive and then parked it up and decided to re-check the oil level... I undid the fill plug and a load of frothy foamy oil spilled out, I had just filled it to level with the fill plug not 1/2 an hour earlier.. and spilling out came this smelly oil milkshake.

That's when I read the service manual ( in the back of crazy Al's race world and repair manual - which I had bought for the copied OE workshop manual reprints in the back 1/3 ... not the long winded story-telling in the front 2/3's ) and saw all the NON EP requirements... I drained it again, filled it with some engine oil and drove it again... no milkshake, so I concluded that the EP additive must have been causing it.

lesson learned, and never used EP oil in a 128 transaxle again

SteveC

 

[Jeff Stich]

As I posted at the top of thread, Staylube from napa as Jeff Stich says. I got that off this board. The formulation now is gl5- not gl4.

The formulation hasn't changed, you simply have the wrong Sta-Lube type & part number shown in your photo above (neither of which were from myself or this board).

The correct Sta-Lube GL-4 formula is SL24229 (1-quart size), SL24239 (1-gallon size) or SL24259 (5-gallon size), & is still widely available today.



A brief description of this product from the parent company (CRC Ind.):

https://www.crcindustries.com/products/api-gl-4-multi-purpose-gear-oil-85w90-5-gal.html

"GL-4 Hypoid Gear Oil has low pour points and high temp properties to provide lubrication over a wide temperature range. This versatile lubricant contains anti-rust and anti-wear EP additives to provide the corrosion protection in drives and hypoid gears. It is not corrosive to copper, bronze, or other non-ferrous alloy bearings and bushings."

 

[Jeff Stich]

Maybe now we've gotten to the bottom line?...Matt Brannon explains further:

The 850 based transaxle in your OTAS uses Porsche type sintered metallic round rings and steel sliding sleeves. The 128 and X1/9 trans, while packaged differently uses the same exact sliding sleeves and synchros, without an ounce of “brass” to be found anywhere in the trans, just like yours. Let me repeat, the same exact synchro rings and sliding sleeves are used in all three cars’ gearboxes.

Despite the owners manuals for 850s calling for an 90 WT EP modifier, this recommendation was halted in 1972-on for the 128, X1/9, and even all of the 124 transmissions. See attached owner’s manual recommendations for 1972 128.

I and Jon Logan at Midwest-124 only use 90 Wt Mineral Oil GL-1 (Factory recommended for 128, X1/9 and 124) or Redline MT90 GL-4 or Redline MTL GL-4 (closest synthetic to the original GL-1).

`````````````````````
So there you have it.

No, we don't "have it".

The factory-recommended oil for the 850 trans is SAE 90w EP due to its hypoid-type final drive. The factory-recommended oil for those other non-hypoid Fiats is non-EP 90w (GL-1).

As fiatfactory said, it's apples vs. oranges.

I would think long & hard about having my 850 transaxle rebuilt by someone using (or recommending) a gear oil that will simply end up destroying it. Especially if that transaxle has a rare &/or expensive low-ratio ring & pinion gearset in it.

 

[ramona300]

That's a little unfair to just one manufacturer of oils... it should be something more like....

This is what an NON EP oil in an application that requires EP additives will do - it's the pinion contact face in the hypoid configuration of final drive gears that requires the EP additives.

Extreme pressure additive - Wikipedia

en.wikipedia.org

Spiral bevel gear - Wikipedia

en.wikipedia.org

SteveC

It's my fault I used the Redline MTL. I was following advice from this forum. I never read the label till after I destroyed the pinion. On the back, it clearly states not to be used with Hypoid gears!

 

[fiatfactory]

Ummm...I think you meant to say "...never used EP oil in a 128-X1/9 transaxle again"?

I mean, most of this thread has us agreeing that the 850 transaxle requires EP oil.

yes, precisely...never in a 128 transaxle again (was late when I typed it - corrected now.)
SteveC