2007 - 2021 Transfer case and Differential fluids

Everyone loves a good oil thread, and debating the merits of Toyota Genuine fluids including 0w20 engine oil, ATF WS and Toyota transfer case fluid. I am basing this discussion on my '21 SR5 4x4 (model USK56L-CRTSKA) with electronically actuated part-time 4WD transfer case. I don't know the extent, if any, that other transfer cases were used in other Tundra models. I am not advocating using products other than specified in your vehicle's owners manual.

The facts:

-according to Toyota parts fiche two version of the transfer case were used: 36100-34170 was used in production from January - November 2007; 36100-34171 was used from November 2007 onward (likely a minor revision).

-Toyota specified 75w90 GL-5 gear oil for the differentials and transfer case in model years 2007 through 2013.

-In 2014 Toyota specified "Toyota Genuine Transfer gear oil LF or equivalent" (SAE 75W) and
"Toyota Genuine Differential Gear Oil LT 75W-85 GL-5 or equivalent".

Discussion:

It is important to understand there are significant differences in the additives of GL-5 vs GL-4 Gear oils because differentials and transfer case gears work very differently.

GL-5 gear oils are intended for hypoid gear sets in differentials. This type of gear set has more "sliding" friction compared to straight-cut and helical-cut gears found in manual transmissions and transfer cases. Thus, GL-5 gear oils contain a higher concentration of sulfur-containing anti-wear additives. These additives corrode "yellow metals" such as brass synchronizers in manual transmissions

GL-4 gear oils are intended for use in manual transmissions and where otherwise specified. They contain a lower concentration of sulfur containing anti-wear additives and are safe for yellow metal components.

Generally, you do not want to use GL-5 in a GL-4 application due to risk of damaged components from incompatible additives; nor do you want to use GL-4 in a GL-5 application due to risk of increased wear.

We can reasonably assume that the shift from

$39 75w-90 GL-5 Limited Slip, Ultra Long Drain 500k Miles, Manual Transmission, Gear/Differential Lubricant (1 Gallon)

75w-90 GL-5 in the differentials and transfer case to lower viscosity fluids in 2014 is to achieve CAFE standards. It also correlated with the second generation ("2.5 gen") model refresh.

Why does it matter?

The short answer is, it probably doesn't matter. My personal opinion is that the change of fluid is to meet CAFE standards and the ambiguity in specification is to satisfy lawyers.

In this case, the same part number for the transfer case is specified for 2007 through 2021, I believe it is reasonably safe to assume that one could use 75w-90 GL-5 where LF 75W is specified. If there were a T-case part number change for 2014 with the change to LF 75W, I would assume that there was a change to internal parts that were not compatible with GL-5 gear oil. I do not like to assume anything; I'd rather know for sure.

Aside from the logistics of buying (or stocking) two different fluids for differentials and transfer case, the later specified fluids are significantly more expensive with lower availability. I would argue though, that the current fluids are likely significantly better quality than the 2013 fluids, but I can't say if it is a better application for the longevity or our vehicles. Personally, I used Red Line MT-LV in my T-case and Mobil Delvac1 75w-90 in my differentials at my last service.

 

Not to rain on your well thought out post, but the transfer case changed for the facelift in 2014. That's why the fluid spec changed. The mechanism to engage 4WD and the chain are different from the Aisin.

2007-2013: Aisin JF1A
2014-2021: Borg Warner (can't find the model #)

https://www.tundras.com/threads/transfer-case-info.55790/

 

Did they change supplier or is it a different part? Toyota doesn’t differentiate from what I could find.

 

Both, it’s a completely different t-case.

It’s a modified version of the one used in Ford and I believe Ram trucks. If you do some digging there are really interesting videos and post about the development of it. Toyota repeatedly broke the samples BW gave them in testing. They eventually had to upgrade several components to meet Toyota’s durability requirements.

 

Good to know, I’ll do a deeper dive into that.

 

Here is one example

Skip to the 19 min mark. Mike talks about the borg warner cases in the 2.5 and 3rd gen Tundra compared to Ford.

 

The later T-case part number is 36100-0C020 Transfer Assembly for the 2.5 Gen according to Toyotapartsdeal.com

I could not get a definitive part number from autoparts.toyota.com or Toyota-usa.epc-data.com