Why a GL5: does this look like hypoid gears?

[kilou]

Hi,

my manual transmission calls specifically for a 75W80 GL5 lubricant. Searching why GL5 lubricants may be required in some manual transmissions I came acrosse this:

"A manual transmission won't usually contain hypoid gears, so it doesn't need an EP oil. Rare exceptions are those transaxles where the crownwheel and gearbox share the same lubricant."
(source: http://yarchive.net/car/hypoid_gear_oil.html)

In the same text I found that:
"..."hypoid" gear tooth shape (if you look at a pinion, the teeth appear twisted)"

So basically if my manual transmission calls for a GL5 lubricant it's because it shares the oil with the crownwheel (which is as far as I understood the differential unit on a FWD car, right??) After checking I can confirm that the differential of my FWD car is built into the gearbox and shares its oil. OK now I'd like to find those "hypoid" gears (twisted teeth) on the differential to make sure the differential uses these type of gears. And looking at the following picture (which comes from a gearbox similar to mine) I cannot find those twisted (hypoid) gears.

Differential view 1:

Differential view 2: the teeth on the gear at the bottom of the image are those of the crownwheel, right? They don't look twisted at all no?

Finally image of a crownwheel with hypoid gears found on google (the twisted gears are obvious here)

So do I have a differential with hypoid gears? If no why would the manufacturer recommend a GL5 lubricant??

Am I completely wrong with what is a crownwheel?

Thanks for any insight.


PS: Car is a Volvo S40 2.0 non turbo with M5P transmission (this model is NOT imported in the US!!)

 

[bruce381]

you are right BUT a GL-5 will not necessarily hurt BUT the MFG may have figured that a GL-4 is to hard to find?
bruce

 

[RogerKlugerAus05]

The instruction book for my 2006 Toyota Corolla calls for GL-4 OR GL-5 75W-90 in the manual transmission, which must incorporate final drive. I want to do the right thing and put in the best oil and from what I read a GL-4 is possibly best. I tend to agree with Bruce that GL-4 is very hard to come by so that is why either GL-4 or GL-5 is recommended. I intend to use Redline MT90 GL-4 75W-90.
Roger

 

[gtx510]

The only OTC GL-4 that I've found is Coastal75W90 and it's dual GL4/GL5. Who wants to use that so you're left with boutique brands and OTC GL-5's...

A GL-4 will shift better and your synchros should last longer. GL-5's EP and FM addditives aren't so friendly for synchros, "too slick" is what is often said.

Honestly, a xW40 or xW50 engine oil would shift better than a GL-5. And it'd offer enough protect for a transmission.
I've used 20W50 (Coastal ________) in Mazda transmissions requiring 75W90 and they shifted much better than they did with GL-5.

But, Liqui-Moly's "voll"synthetic 75W90 is only GL-5 and it shifts really well. M1 75W90, not so good.

 

[1040 WreckerMan]

Hypoid generally refers more to the centerline of the shafts the two gears reside on than the teeth themselves. A hypoid gearset is basically a bevel gear that has a pinion gear above or below the crownwheel (or ring gear as it's commonly known). A hypoid gearset is much stronger than a spiral bevel gear due to the tooth pitch area, however the sliding forces created as a result require different FM characteristics and more EP additives.

You will have to look and see at what angles the pinion and ring gear intersect at. The 2nd pic above it hard to make out, it looks like there might be some "twist" to the gears. However, it looks much more like a helical gearset than a hypoid or bevel gear.

 

[kilou]

It's true that the availability of GL5 oils seems a bit better than GL4. However in my case I can assure that this is not the reason why GL5 is recommended instead of GL4. Indeed the pics above (and my gearbox as well) are built by Renault, a french car manufacturer. Renault works with Elf (now TotalFinaElf), a french oil company that makes ALL lubricants for Renault. Elf has had GL4 lubricants in the right grade for the application since a long time but Renault never recommended to use a GL4 oil in their transmission. This is the same for all french car manufacturers (Renault, Peugeot, Citroen) and most italian ones: they always call for GL5 oils in their manual transmissions (at least on modern cars).

I came to the question of GL5 oils because my gearbox (as almost all Renault gearboxes) use brass synchronizer rings. I heard that GL5 were corrosive to synchros but after a while I discovered on this forum that some GL5 were safe to synchros due to inactivated sulfur-phosphorus additives. However the question remained that some GL5 were too slick for proper synchros operation and that GL4 would do better.

So I'd say at least in Europe the requirment of GL5 oils is not stressed by a poor availability of GL4 oils since these are available in the correct grade by "dedicated" oil companies of car manufacturers. Moreover a lot of European cars (probably outside german ones but I have no real idea) do use brass synchronizer rings that would normally prefer a GL4 (at least a GL5 would have absolutely no benefit).


As for the gear type used in my gearbox, there is tons of pictures on the following website where one guy completely dismantled the gearbox to rebuild it. I've checked all the pics and cannot find a hypoid gearset. You can just look at the pics (pics are on page 1 to 3).

http://www.forum-auto.com/sqlforum/section12/sujet150265.htm

Is there any other reason a GL5 oil may be required for this gearbox? I also heard about GL5 non-hypoid gearoils: why then would we need a GL5 if there is no hypoid gears????

 

[unDummy]

Because it requires it!

Unless you know the strength of the gears, and the load placed on them, don't step down to a GL4 gear oil. Some transmissions need that extra protection to prevent wear. Some gear materials need that added protection.

There is more to GL4, GL5, and GL6 then 'type' of gear.

 

[1040 WreckerMan]

unDummy brings up a good point. A hypoid gear places more "stress" on the teeth than a spur or bevel, etc. gear so it requires more EP adds to control wear. However, a large hypoid gear may actually have less of load per a given area than a smaller bevel gear used in the same application.

In the case of your transmission it maybe that they are just using bevel or helical gears that are subject to higher than normal loads so they spec GL5 to help the longevity of the transmission. I'd imagine to keep the footprint small, the mfg made the transmission as small as possible. Also, do you know what the mfg says the maximum rated hp/tq for that gearbox is? They probably spec the same oil regardless of what car maker uses that trans, however if your application is below the maximum rated power the GL5 oil may not be required.

 

[tom slick]

the gears in your pictures are not hypoid like the picture of the ring and pinion that you borrowed from the 'net.
in your application the gears/shafts run parallel to each other and do not have a sliding action like the ring and pinion gears. the ring and pinion gears/shafts run perpendicular to each other and slide together as they operate.

 

[kilou]

I'm for sure not comfortable in stepping down to a GL4 if the manufacturer calls for a GL5 and will definitely not take any chance with that. However it's still a mystery for me why do french manufacturers always call for GL5 in a FWD gearbox....moreover when they use brass synchronizer rings!! I'm not really concerned with the "good shift abilities" of my gearbox but I'm really concern with its longevity. This is why I'm also exploring the area of gear oil additives (see my other posts on that subject). I know that GL5 using inactivated borate EP additive are supposed to be safe for yellow metals but I'm still not sure whether this is also valid for sulfur-phosphorus EP additive packages...which most GL5 still use today I guess. It's never said on a GL5 if it uses S-P or inactivated borate EP additives so when a car calls for a GL5 yet uses brass synchros it's almost try and see what happens. But going to a GL4 to help synchros may stress the bearings or pignions if the box really require GL5 protection for these so it's not a way to go too. Definitely very strange how these gearboxes are built and the fluid they ask for!!! Anyway thanks for your kind help, very appreciated.

 

[1040 WreckerMan]

The French car markers may work with the oil blenders to have GL5 that is compatible with the brass syncro's since that is what is common in your part of the world.

Many times the data sheets for an oil will indicate what EP additives the oil uses. If it is available, Delo ESI gear lube is GL5 rated and uses borate. We use about 75,000 gallons of ESI a year at work and have had great luck with it compared to the shell oil we were using.

I doubt you will ever get a conclusive answer unless you are able to speak with an engineer at Renault who is directly involved with gear box design and lubrication and ask them why they spec GL5. Again, my guess would be they are using small gears to save space which creates high contact loads on the gear teeth so a better EP package is necessary.

You could also try talking to the local oil distributor for the brand you prefer as they should have more technical data sheets than are commonly available.

 

[bruce381]

Delo ESI is a sleeper gear oil runs out to 100,000K or so eaton approved as I remember and give low wear with LONG life.

1040, Lubrizol screwd up your sample of bio fuel additve but is now on the way.

bruce