Difference between GL-4 & GL-5?

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Been running Amsoil MTG 75w90 in my 08 corolla 5-speed, which is a GL-4 fluid. Toyota suggests a GL-4 or GL-5.

Am i running one of the best fluids, or am i asking for more bearing wear vs. a GL-5?

It seems to be performing smoothly when warm, but is still a little notchy feeling when cold.

Any tips?
 
My understanding is GL-5 would have more antiwear additives. I think the difference is more important in a differential. For a manual tranny a GL-4 would seem to be just fine.
 
Originally Posted By: TallPaul
My understanding is GL-5 would have more antiwear additives. I think the difference is more important in a differential. For a manual tranny a GL-4 would seem to be just fine.


Thanks for the tip.

Just heard some horror stories about those running gl-4 causing bearing issues down the road.
 
The MTG will give your bearings excellent protection and the frictional properties of that fluid will also protect the synchronizers better and allow easier shifting than a GL-5. There are few GL-5 fluids that would work well in a manual gearbox. Redline has one, but most 75W-90 GL-5 gear oils have viscosity and frictional properties that are designed for differentials and not synchronizers. Redline also makes a GL-4 called MT-90 and it also works well in manual gearboxes that call for 75W-90 viscosity gear oil.
 
Originally Posted By: 3Toyotas


Just heard some horror stories about those running gl-4 causing bearing issues down the road.


I would love to see the link and evidence for this. Many transmissions run ATF and suffer no ill effects. While it is true that a GL-5 by design contains more HD AW and EP additives, this does not mean it will extend transmission life. Bearing life? I doubt it. Maybe gear life, but not always other parts with rotational contact. Because simply put a transmission is not nearly as stressed as a differential. Most MT's don't even get warm (aside from transferred engine heat)
 
Isn't the main difference between GL4 and GL5 for enhanced protection of hypoid gears? Hypoid gears generate much more pressure between the gear teeth than other gear designs.

Bearings don't usually have anywhere near the same pressures.
 
Not to sound thick here, but don't many FWD manual and automatic transmissions have the differential sharing the same lubricant? Is this differential less stressed than what Pablo suggests in "Because simply put a transmission is not nearly as stressed as a differential."
 
Originally Posted By: Big Jim
Isn't the main difference between GL4 and GL5 for enhanced protection of hypoid gears? Hypoid gears generate much more pressure between the gear teeth than other gear designs.

Bearings don't usually have anywhere near the same pressures.


That is correct. The GL-5 lubricants are designed to cope with the sliding action of hypoid gear interfaces. Quite often, but not always [dependent on the chemistry], GL-5 type lubricants are not compatible with synchromesh transmissions.
 
Originally Posted By: BearZDefect
Not to sound thick here, but don't many FWD manual and automatic transmissions have the differential sharing the same lubricant? Is this differential less stressed than what Pablo suggests in "Because simply put a transmission is not nearly as stressed as a differential."


I don't know of any transaxles that use hypoid differential gears. If you don't have hypoid gears, you don't need a very high level of EP (extreme pressure) additives.

Hypoid gears were developed to lower the floor pan on rear wheel drive cars. The pinion gear mates with the ring gear near the bottom of the differential, allowing the driveshaft to be lower, and thus the floor pan lower.
 
Originally Posted By: BearZDefect
Not to sound thick here, but don't many FWD manual and automatic transmissions have the differential sharing the same lubricant? Is this differential less stressed than what Pablo suggests in "Because simply put a transmission is not nearly as stressed as a differential."


In vehicles with transverse-mounted engines (typical American and Japanese fwd cars), the differential generally uses helical gears. Whereas the differentials used with longitudinally-mounted engines (which Pablo is referring to) use hypoid gears in all modern automotive applications... seeings how the torque has to make a 90 degree turn.
 
Originally Posted By: Big Jim


I don't know of any transaxles that use hypoid differential gears. If you don't have hypoid gears, you don't need a very high level of EP (extreme pressure) additives.

Hypoid gears were developed to lower the floor pan on rear wheel drive cars. The pinion gear mates with the ring gear near the bottom of the differential, allowing the driveshaft to be lower, and thus the floor pan lower.


Lets see, Porsche, Subaru, Audi, Alfa Romeo all use hypoid diffs in transaxles for starters.

Hypoid gears are much stronger for a given crown wheel diameter than plain pinion on centreline spiral bevel diffs, thanks to the greater tooth engagement of the pinion with the crown wheel. This obviously increases the further away from the crown wheel centreline the pinion engages but at a decrease in efficiency and an increase in heat and load on the teeth.
 
I've serviced several makes and models that had a transaxle that required a GL-5 hypoid gear oil in the diff portion of the transaxle. Subarus and Acura Vigor/TL come to mind.

In addition to lowering the floor pan, hypoid gears carry greater load as several gear teeth are always in contact to share the load. Also, they operate quietly (when set up correctly).
 
Hypoid gears [pinion and ring] slip a little as they engage and rotate together.
Under load, this is a very real concern. So for them, you'd better get the dedicated sauce. GL5 is usually appropriate for them.
If you have a manual trans or transaxle, a modern GL4 dedicated to good shifting is best.
 
My '02 Hyundai Accent specified GL4 for it's manual transmission. My understanding was that GL5 fluid is not compatable with yellow metals.
 
No difference except coefficient of friction. GL specs do not supercede. Some people use M1 GL-5 in MTF and it does fine. I think the difference is neigh.
 
Originally Posted By: Whitewolf
Originally Posted By: Big Jim
Isn't the main difference between GL4 and GL5 for enhanced protection of hypoid gears? Hypoid gears generate much more pressure between the gear teeth than other gear designs.

Bearings don't usually have anywhere near the same pressures.


That is correct. The GL-5 lubricants are designed to cope with the sliding action of hypoid gear interfaces. Quite often, but not always [dependent on the chemistry], GL-5 type lubricants are not compatible with synchromesh transmissions.
Exactly. The older additives that made GL-5 gear oil handle the extra stress on the hypoid gear teeth were damaging to the yellow metal (brass or bronze) in synchromesh synchronizers. Modern GL-5 additives are not damaging to the yellow metals...read the label on the container to find which GL-5 gear lubes are also good where GL-4 is specified.
 
Originally Posted By: onion
Originally Posted By: BearZDefect
Not to sound thick here, but don't many FWD manual and automatic transmissions have the differential sharing the same lubricant? Is this differential less stressed than what Pablo suggests in "Because simply put a transmission is not nearly as stressed as a differential."


In vehicles with transverse-mounted engines (typical American and Japanese fwd cars), the differential generally uses helical gears. Whereas the differentials used with longitudinally-mounted engines (which Pablo is referring to) use hypoid gears in all modern automotive applications... seeings how the torque has to make a 90 degree turn.

The 1980s-early 1990s Saab 900 had FWD and a longitudinal engine. The AT was filled with Ford Type F, but at the hypoid gears, there was a separate reservoir that required 80w90 GL-5 gear oil.

The Chrysler LHS and Dodge Intrepid had a longitudinal engine and FWD. The AT took ATF+3 or ATF+4, but the differential was separate, and required 80w90 GL-5 gear oil.

The 5th generation VW Passat had a longitudinal engine and FWD with AWD being optional. I never saw an AWD Passat, but every FWD Passat had an AT filled with some proprietary ATF, then the differential was seperate. It called for something unique: SAE 80 GL-4.

Most subaru cars have a longitudinal engine, and in the cases of Manual transmissions, GL-5 oil is required. Automatics called for Dexron ATF, and there was also a separate reservoir for GL-5 oil. Viscosity varied by temperature. SAE 90 when temps would not drop below freezing, SAE 80w90 for almost all temperatures, and SAE 75w90 in extreme cold.

In short, ATF can't lubricate a hypoid diff of any kind, and GL-5 is almost always required, with very few exceptions.
 
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