This will be my 3rd time doing this service on my 2008 T4R SR5 4x4. Every time i do this service I’m showing minimal fluid wear on my front diff, transfer case, and especially rear diff. For those wondering I am using Valvoline full-synthetic 75w-90 because it is cost effective and replaced my fluid every 30k.

I have been using my car for 100% normal drives and 0% for towing or off roading.

I have researched on the forums and had little to no luck.

My goal is to not be cheap and at the same time not waste money on changing gear oil too early.

For fully synthetic gear oils, what service mileage interval have you guys been comfortable with...35k? 40k? 45k?

And what gear oil did you use?

I’m thinking about using walmart brand super tech full synthetic for my next service since its made by Warren Oil.

Please share your experience, thank you!

Normal driving and no towing should allow you to keep diff fluids for 60K.

I was using Valvoline too but last time (2 months ago) I splurged and went with Amsoil, front/rear/Tcase. Had no issues with Valvoline but decided to upgrade. Rear dif and Tcase are always clean at drain, 30K, but front dif is usually dark at least. I'd say for your service, which is same as mine, we're good for 60K interval easily.
I have about 300 miles on 4R since change and MPG monitor has settled at 18.0-18.3 for past two weeks, never done that before, all last summer stayed at 17.3.
Only other reason I could see for change is wheel alignment, which I did myself and fine-tuned toe.

i say every 50k after the 100k mark.

Stupid question but does this include leaving the original fluid in for that time, if you don't tow or off road?

Yes, original fluid is just plain 75W-85 gear oil with LS (Limited Slip) additive and perfectly okay for 60K.

I bought my '17 SR5 with 20k miles on it.
Changed the diffs and T-case at 30k, just for my personal baseline.
Will do again at every 50k or after water crossings from now on.

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replace differential at 75k and drain and fill transmission at 100k on daughters and wife's 4runners. Pavement only, typical driving, very little towing. Use mobil 1 synthetic, valvoline synthetic in trans. Both trucks now over 250k, zero issues.