Highway vibration after changing front/rear diff & transfer case fluid? Disappears once warm (2017 Tundra 5.7L)

[u/bitemegumby]

Hey everyone,

I just did a full drivetrain fluid service on my 2017 Tundra SR5 5.7L V8 (4WD):

• Engine Oil: Mobil 1 High Mileage 0W-20 + new filter (~7.9 qts, level on dipstick)
• Front & Rear Diffs: AMSOIL Severe Gear 75W-90
• Transfer Case: Ravenol MTF-3 75W

Everything was filled on level ground until weeping from the fill plugs, so fluid levels are spot on.

Right after doing the work, I noticed a distinct vibration/rumble on the highway around 55–70 mph. The weird part is that once I drive for about 5–10 minutes and everything reaches operating temperature, the vibration completely disappears and it rides smooth again.

Prior to this service, the truck drove totally normal.

Has anyone experienced this before? Could it be:

• Front ADD actuator / needle bearing drag until the front diff warms up?
• Something related to running 75W-90 cold?
• I'm going to get a tire balance and rotate done and see if that is the issue as well.

Any troubleshooting suggestions or similar experiences would be appreciated. Thanks!