Toyota MT - "Gear oil API GL-4 or GL-5"

[JerryBob]

My owner's manual for my 4WD Tacoma says for my transfer case and manual transmission to use "Gear oil API GL-4 or GL-5".

I changed the factory fill last fall with Redline GL4 Synthetic, per the recommendations at tacomaworld.com.

Is it the case that GL-4 and GL-5 are just different, or is one better than the other? I know that Gl-4 is supposedly easier on yellow metals.

Is Gl-4 the best choice for my truck? Or should I have used a Gl-5?

 

[simple_gifts]

Not sure toyota would have speced a GL4 if some component of GL5 is necessary for long MT life.

Other than the factory fill, I've been using GL4 only lubes for my Toyota MT. Shifts like new.

 

[Hootbro]

You are over thinking it. If GL-4 was a problem, it would not be specified at all.

 

[Rand]

GL-5 has more additives, it can also cause shift quality to be poor(in MT).

gl-4 should be more than fine in both.


Gl-5 would be fine in the transfer case, but I would avoid in a MT unless your manufacturer requires it (such as subaru or porche)

 

[JHZR2]

Most manual transmission "specific" fluids (i.e. GL4, such as the Redline ATFs) contain about 40% to 60% of the EP additive of differential lubes (i.e. GL5) with inactive or buffered sulfurs. GL4 has come to infer a gear lube with the above percentages of EP additive.

Differential lubes and motor oils became obsolete for most passenger car MT use, and synchromesh-type fluids appeared on the scene (such as the GM Synchromesh fluid), drivers have had better shifting due to better synchro engagement, attributed to the specialized friction modifier used in these lubes. This specialized friction modifier is better for metallic and composite synchros in terms of shifting and life.

Manual Transmission fluids use a different friction modifier specifically designed for synchro engagement, a modifier that does NOT contain the same chemical compounds as do differential lubes.

Amsoil does have some MT-specific fluids, one that should play in your range of viscosity. Redline does as well, but personally I've always been disappointed with the shift feel of redline after the honeymoon period, while amsoil seems to stay more consistent.

 

[4wheeldog]

I have had Redline MT90 in the transmission and transfer case of my '05 Tacoma 6spd, and I have to say, it is the answer. The original fluid made shifting in cold weather problematic, and RL 75/90 GL5 was better, but not great (You could beat the syncros, if you were in hurry).

The MT90 works great in all conditions, and I just received a new batch, to replace the stuff that has been doing so well for 100k miles. I cannot recommend it highly enough.

 

[JerryBob]

Originally Posted By: 4wheeldog
I have had Redline MT90 in the transmission and transfer case of my '05 Tacoma 6spd, and I have to say, it is the answer. The original fluid made shifting in cold weather problematic, and RL 75/90 GL5 was better, but not great (You could beat the syncros, if you were in hurry).

The MT90 works great in all conditions, and I just received a new batch, to replace the stuff that has been doing so well for 100k miles. I cannot recommend it highly enough.


According to my Amazon history (where I bought it), "Red Line (50304) MT-90 75W-90 GL-4" is what I purchased in Sept. I am quite happy with it. Even in Winter, it shifts nicely.

I just want to make sure it is a better choice than the Gl-5.

Based on the responses, I am going to leave it in there and be happy.

 

[bullwinkle]

Leave the Red Line in there-I put RP Severe Gear 75W90 in my xB manual trans 25K miles ago trying to help with syncro problems, getting worse & will likely need them replaced (am at 62K now). Looking online, only MT-90 or OEM Toyota gear oil appears safe. Just because Toyota says their MTs can handle GL-5 doesn't mean that they can-because they CAN'T!

 

[antiqueshell]

Originally Posted By: Rand
GL-5 has more additives, it can also cause shift quality to be poor(in MT).

gl-4 should be more than fine in both.


Gl-5 would be fine in the transfer case, but I would avoid in a MT unless your manufacturer requires it (such as subaru or porche)


This is THE BEST ADVICE.

GL-4 ONLY in the manual transmission

GL-4 or 5 in the transfer case.

 

[MolaKule]

Originally Posted By: JerryBob
Originally Posted By: 4wheeldog
I have had Redline MT90 in the transmission and transfer case of my '05 Tacoma 6spd, and I have to say, it is the answer. The original fluid made shifting in cold weather problematic, and RL 75/90 GL5 was better, but not great (You could beat the syncros, if you were in hurry).

The MT90 works great in all conditions, and I just received a new batch, to replace the stuff that has been doing so well for 100k miles. I cannot recommend it highly enough.



According to my Amazon history (where I bought it), "Red Line (50304) MT-90 75W-90 GL-4" is what I purchased in Sept. I am quite happy with it. Even in Winter, it shifts nicely.

I just want to make sure it is a better choice than the Gl-5.

Based on the responses, I am going to leave it in there and be happy.



What you want is a dedicated 75W90 Manual Transmission fluid which will have a GL-4 protection rating.

The Redline MT-90 should serve you well. Amsoil MTG is a good choice as well.

 

[aquariuscsm]

From what I've heard,GL5 lubes have adds that will prevent the synchros from functioning properly,thus causing gear clash. Redline MT90 or Amsoil MTG are you best choices.

 

[MolaKule]

Originally Posted By: aquariuscsm
From what I've heard, GL5 lubes have adds that will prevent the synchros from functioning properly, thus causing gear clash. Redline MT90 or Amsoil MTG are you best choices.


It's primarily the lack of proper friction modification additives in GL-5 differential lubricants that can cause gear clash in the synchros. Secondly, GL-5 differential lubes have viscosities on the higher end of the 90 weight scale, causing sluggish movement of the shifter fork.

Subaru does specify a GL-5 synchromesh lubricant for their manual tranny, but that is because the tranny shares a common sump with the hypoid differential.

 

[aquariuscsm]

Originally Posted By: MolaKule
Secondly, GL-5 differential lubes have viscosities on the higher end of the 90 weight scale, causing sluggish movement of the shifter fork.


What exactly does that mean Mola? The actual force needed to move the shifter stick?

 

[MolaKule]

Manual Transmissions and Lubricants

See post #2813713

 

[Greasymechtech]

Besides Redline MT90 MT85 and Amsoil MTG, Ford has a couple 75w90's GL4 manual transmission gear oils.
Nissan/GM/Kia/Hyundai/Dodge also have great 75w85 GL4 manual transmission oils.

Stick with GL5 for the diffs and xfer case.