Observation on Why MG Specifies 85W90 GL4 in the 6-Speed Gearbox

[Bonaventure]

Only reason I can fathom why MG specs GL4 in the 6-speed gearbox (yet GL5 is spec'd in the CARC bevel box) is that there must be yellow metals (brass) in it. 

The sulfur based EP (extreme pressure) additives in GL5 gear oil attack yellow metals (corrosion).

The only 85W90 GL4 I can find locally available is CRC Industries Sta-Lube:

http://www.crcindustries.com/products/api-gl-4-multi-purpose-gear-oil-85w90-32-fl-oz-SL24229.html

Napa Auto Parts carries it.  Nothing particularly special about gear oil, and this option is 1/2 the cost of buying ENI Gear MG/S 85W90 online (eBay/Amazon)

Further evidence can be found in the ENI Gear MG/S 85W90 Product Data Sheet here:

https://travel.eni.com/catalog/products/documents/001201_14_en_FR_1_106.pdf
 
"...noncorrosive to steel, copper and other metals and alloys..."  i.e.: it has a GL4 compliant additive package that doesn't attack yellow metals. 

There must be yellow alloys in the MG 6-speed box, best to use only a GL4 gear oil in there (no sulfur additives).

[Chesterfield]

Makes sense to me

[ITSec]

You raise a good point, but I have a CARC bike with a six-speed gearbox - a 2008 Norge - and it has had nothing but Mobil1 75w90 Syn Gear Lube in both the gearbox and final drive since I bought the bike. The spec sheet for this oil (https://www.mobil.com/english-us/passenger-vehicle-lube/pds/glxxmobil-1-syn-gear-lube-ls-75w90) mentions only GL-5, but it has not created any apparent damage to the bike in 137,000 miles. The manual for that bike mentions AGIP MP and MP/S lubes - which both have a GL-5 spec and thus my choice.

I don't understand why there would be a need to introduce brass or other components to the newer machine that would make the move to a GL-4 advisable. If the synchros or other pieces were resistant to corrosion or other damage, why move to what would apparently be s step back and use a softer metal?

Perhaps someone who has taken one of these units apart would offer some insight? I need to do a fluids change on my Stelvio in the next week!

[Arizona Wayne]

Up to now I've always used GL-5 tranny, rear end oil in Guzzis w/o molly with no regrets for 33 years.  GL-4 oil has been replaced by GL-5 oil for a long time.  Are you sure you aren't misreading what MG recommends?

[rodekyll]

I didn't know that the non-carc 6-speeds had been around for 33 years.

[pete roper]

God's teeth!  Make it stop!

[Arizona Wayne]

I didn't know that the non-carc 6-speeds had been around for 33 years.

No one has said that but you. I'm just curious why all of a sudden  MG recommends GL-4 instead of GL-5 oil in the tranny after all these years. 

[ITSec]

God's teeth!  Make it stop!

I appreciate the sentiment, Pete - but this is not a (brand) oil thread but a question about the construction of the transmission (gearbox) and the spec. A fair question by the OP and I certainly would also appreciate some clarification as to whether there is any reason to pay attention to the GL-4 spec. At this point, I'm inclined to ignore it - but in some cars (VW and others) it has in the past reportedly been important.

I should note that in my electronic copy of the 2012 Stelvio owners' manual, the description of gearbox and final drive oil doesn't say anything about either GL-4 or GL-5 - it simply states "AGIP GEAR SAE 80 W 90" for the final drive/CARC and "AGIP GEAR MG/S SAE 85 W 90" for the gearbox. As I noted in my earlier post, AGIP's own documents show these as GL-5 as best I can see.

[ITSec]

No one has said that but you. I'm just curious why all of a sudden  MG recommends GL-4 instead of GL-5 oil in the tranny after all these years. 

I can't tell that they do - the owner's manual for the Stelvio that I got says nothing about GL-4 or 5, and only gives AGIP product names. When I look the AGIP info up, it says these are GL-5 lubes. However, the OP's post implies that the docs he got for his 2016 (I believe) list a GL-4 spec and I have no reason to argue with that since I have a different model year manual. Since I can't recall any changes to the gearbox in the 2011-2017 period, I suspect the OP is either mistaken or there's a typo somewhere. However, we've all seen cases where the manuals or wrong or changes occurred with no notice to buyers or dealers, so it's worth clarifying.

[Chesterfield]

I appreciate the sentiment, Pete - but this is not a (brand) oil thread but a question about the construction of the transmission (gearbox) and the spec. A fair question by the OP and I certainly would also appreciate some clarification as to whether there is any reason to pay attention to the GL-4 spec. At this point, I'm inclined to ignore it - but in some cars (VW and others) it has in the past reportedly been important.

It`s probably not important but from an engineers perspective if GL-4 is the specification for colored metal parts than a good engineer would advise using it. Just read up on Alaska Airlines Flt 261. A certain grease was specified for the horizontal stabilizer jackscrew and another was substituted. Over many years of service the threads were worn thin from not lubricating properly and also using a non-specified grease. This resulted in the failure of the horizontal stabilizer to maintain position, which resulted in the death of 88 soles

[Huzo]

It`s probably not important but from an engineers perspective if GL-4 is the specification for colored metal parts thadn a good engineer would advise using it. Just read up on Alaska Airlines Flt 261. A certain grease was specified for the horizontal stabilizer jackscrew and another was substituted. Over many years of service the threads were worn thin from not lubricating properly and also using a non-specified grease. This resulted in the failure of the horizontal stabilizer to maintain position, which resulted in the death of 88 soles

Souls...176 soles.
Is that the one where they had a runaway trim, and the pilot/s had to exert so much back pressure on the column that the nut stripped on the shagged threads on the jackscrew ?

[Bonaventure]

God's teeth!  Make it stop!

I actually laughed hard enough to have spewed coffee, had I a mouthful at the time of reading that !!  Even have to probably agree, oil discussion can be the epitome of OCD tendencies and I have a few. 

As it stands, after posting all that two things occurred this morning.  I checked the owner manual 2016 that came with the bike.  Here is the page below.  Then considering that I am performing the first service myself, I surrendered to Piaggio/Guzzi and have just finished ordering all the special sauce ENI stuff by eBay right down to the i-Ride PG 10W60 engine oil, UFI filter (30153000), and both the ENI gear oils.  Essentially done as insurance in the event of a warranty claim being contested...

[Bonaventure]

Interesting that one must look at the French version pg 229 to understand which "transmission" they're referring to on the English page 228.   

[ITSec]

Interesting that one must look at the French version pg 229 to understand which "transmission" they're referring to on the English page 228.   

It's a longtime issue that the Italian to English (and most other languages) translation results in the complete confusion over what a transmission is... most of us avoid the term and talk about the gearbox and final drive instead. I even wrote those terms into my owner's manual of one machine some years ago. 

[rodekyll]

No one has said that but you. I'm just curious why all of a sudden  MG recommends GL-4 instead of GL-5 oil in the tranny after all these years. 

Not really.  I said I didn't know that the 6-speed had been around that long.  See the quote?  My point was that what might have been recommended in other gearboxes for the last 33 years has no relevance to the needs of a CARC 6-speed.  That's all.  :)

[Lannis]

I can't tell that they do - the owner's manual for the Stelvio that I got says nothing about GL-4 or 5, and only gives AGIP product names.

My Stelvio owner's manual specifies "AGIP GEAR SAE 80 W 90" for the final drive/CARC and "AGIP GEAR MG/S SAE 85 W 90" for the gearbox.

When you buy these and look at the bottles, the gearbox oil says it's GL-4 and the CARC oil is GL-5.

Interesting as a theoretical exercise (which I think this is, as noted), but for me, who simply shortcuts all the oil mania by buying and using what the manufacturer specifies, it's a bit moot!

Lannis

[pyoungbl]

A question for Pete.....Am I correct in thinking that the Guzzi box (5 or 6 speed) does not have brass synchronizers at all, just shift dogs on the gears?  All this talk about GL4 vs GL5 makes my head hurt.

Peter Y.

[rodekyll]

It's a quart of oil.  It's not expensive.  You change it once a year or less.  What is the problem with using the mfgr's recommended grade? 

[Lannis]

It's a quart of oil.  It's not expensive.  You change it once a year or less.  What is the problem with using the mfgr's recommended grade?

I have such an excellent answer to that question that I'm glad you've asked it, and it would make an excellent Master's thesis in "Anthropology of Social Interaction".

But I've probably worn it out here in the past 9 years, so will desist.

Lannis

[Tusayan]

I have such an excellent answer to that question that I'm glad you've asked it, and it would make an excellent Master's thesis in "Anthropology of Social Interaction".

This particular interaction starts with a customer reading paid product placement advertising (the AGIP advert) in a piece of literature that was bought by that customer, and in which he would expect to place his trust without fear of Piaggio's other interests.  It's not a situation that engenders a lot of confidence in whatever else might be recommended.

[Chuck in Indiana]

My guess is it was cut  (with scissors ) and pasted into a manual  well before the computer age.  The tradition continues. . Take info from a Guzzi manual with a healthy dash of salt.

[pete roper]

A question for Pete.....Am I correct in thinking that the Guzzi box (5 or 6 speed) does not have brass synchronizers at all, just shift dogs on the gears?  All this talk about GL4 vs GL5 makes my head hurt.

Peter Y.

There are no synchs in any Guzzi box. There may be one bearing with a brass cage in the five speed. I've never seen it fail through use of the *Wrong* oil.

[Bonaventure]

When you buy these and look at the bottles, the gearbox oil says it's GL-4 and the CARC oil is GL-5.

Lannis

Mystery solved, thank you sir!!   Likely that MG's owner manual proof reader simply let a flip/flop typo slip by and the GL's are reversed.  I have both of those bottles on order by the way.

Even all this confusion doesn't match the catch 22 in my Subaru.  Brass synchros in the manual transmission but the front differential (hypoid) also sits in the same chamber and is lubricated by the gearbox oil.  Hypoids need GL5, most retail GL5 are tough on the brass synchros.  Add to that you can't run a GL5 with friction modifiers or the synchros won't hook up as nice.  I was lucky enough to find a mineral gear oil by ENEOS that was GL5 but safe for yellow metals and no friction modifiers.  Subaru takes the cake for that conundrum. 

[redhawk47]

My V7II manual - PDF - says API GL-4 and GL-5
the printed manual that came with my bike says the same.

[bulwnkl]

So, why is this not the most reasonable (and thus probable?) answer:

1)  The transmission lacks any high load, high-offset hypoid gearsets (right? or no?), and so does not need a GL-5 level of EP protection.
2)  The tranmission is not synchronized like a typical car tranny.
3)  Since a GL-4 is thoroughly sufficient to protect the transmission given the above, that is where the spec. is set.


ALL GL-5 gear oils are also GL-4 gears oils.
Most modern GL-5 gear oils from at least the past quarter century contain the right sulfur-phorphorus EP additive system and contain sufficient metal deactivators that they are yellow-metal-safe.

That is why no one has had any issues when using GL-5 gear oil even in gearboxes that have yellow metals.

[Lannis]

This particular interaction starts with a customer reading paid product placement advertising (the AGIP advert) in a piece of literature that was bought by that customer, and in which he would expect to place his trust without fear of Piaggio's other interests.  It's not a situation that engenders a lot of confidence in whatever else might be recommended.

Can I have permission to use this quote as part of the "statement of the problem" example in my thesis?      

[Tom H]

Maybe I'm wrong and full of it. I went the simple route.

Sta Lube GL-4 in the gearbox/transmission/ thing that shifts the gears and the same in the rear end/transmission/ rear drive thing that connects to the rear wheel. I use this in my loop 4 speed (which I have read has issues with GL-5???? shrug) through my EV.

Only twice have I had an issue in 30+ years, was a blown up output shaft bearing in a 5 speed (shifted smooth until the day it would not shift, the trans housing was even worn through where the bearing sits) and a broken tooth in the 5 speed rear drive ( most likely due to my bad driving habits in my youth. Yes, Eldos can do wheelies two up or solo )

Tom

[Chesterfield]

Is that the one where they had a runaway trim, and the pilot/s had to exert so much back pressure on the column that the nut stripped on the shagged threads on the jackscrew ?

Yes, something like that. http://www.nytimes.com/2002/12/11/us/alaska-airlines-crash-that-killed-88-tied-long-failure-lubricate-tail-control.html

[Ncdan]

Ok, as I realize when it comes to Guzzis I�m not the sharpest knife in the drawer. I�m nearing  the time to change the oil in my tranny and rear end in my 07 Calvin and was going to use a good quality 75-90 synthetic that says on the bottle for the 4and 5 types of oil. Am  I going to be ok?
These types of conversations are confusing for an old guy who has  ridden thousands of miles on all kinds of bikes and never changed anything but the oil.

[Bonaventure]

Ok, as I realize when it comes to Guzzis I�m not the sharpest knife in the drawer. I�m nearing  the time to change the oil in my tranny and rear end in my 07 Calvin and was going to use a good quality 75-90 synthetic that says on the bottle for the 4and 5 types of oil. Am  I going to be ok?
These types of conversations are confusing for an old guy who has  ridden thousands of miles on all kinds of bikes and never changed anything but the oil.

Based on everything discussed, I'd say it will be okay.  I've caved and ordered the two ENI gear oils shown in the manual, mainly since it's still new and under warranty if something would fail I can show Piaggio receipts for the exact oils they pimp in the manual, maybe leave them less room to squirm about paying the repair.  Not that I actually expect anything major to break, this bike appears to be built like a tractor ...