Originally Posted By: btanchors
Here is a link to an article describing the change Toyota made to the supplier of the Transfer Case beginning with model year 2014:
Borg-Warner Transfer Case
Note this excerpt from the article:
Quote:
"BorgWarner’s transfer case uses an
electromagnetic-based synchronization system to synchronize the front and rear axle speeds before locking them together. Unlike conventional mechanical synchronization systems, BorgWarner’s electromagnetic-based system provides a smooth, quiet and consistent transition from two-wheel to four-wheel drive,” according to a BorgWarner press release."
This implies there
could be a clutch of some type that makes the engagement of 4WD smoother than with the original supplier of the transfer case.
I am speculating here, but if a clutch is indeed involved in the
new design, then frictional characteristics of the fluid are important for proper clutch operation. I am willing to bet that using a 75W-90 would cause no problems, except during engagement of 4WD. Since 75W-90 is over 3 times thicker than 75W at operating temperature, I could easily see how engagement/disengagement of the clutch could be affected.
So, I think my decision is made - I am only going to use the OEM 75W fluid in this unit.
The speculation that post 2014 Xcase has some type of clutch being 'added' implying it being a new design is ...... NOT true.
Both new and old models Xcase contain similar components in bearings, spur/spline gears,planetary gear sets, shift forks and synchroniser etc.
Only mechanisms to activate shift forks has changed, instead of traditional lever or electric motor activated types.
This shift activation mechanisms (that shift between 2WD and 4WD AND shift between High and Low gear ratios ) are not in contact with Xcase gear oils anyway. Hence this new type of electro-magnetic activation of shift forks ...... has no relationship to gear oils or its viscosity grades.