I have a 2020 IS300 RWD Fsport and last year had the transmission and differential serviced at Longo Lexus in Southern California. The car then had about 29k miles. It has about 32.5k miles now, and am wondering how often I should be servicing the transmission and differential over time. The car is mostly city driven in stop-and-go Los Angeles traffic. I'm planning on keeping the car for at least another five years. Lexus doesn't provide maintenance service intervals for the transmission or differential, although they definitely need to be serviced, I'm just unsure how frequently. Every two years? Three?

 

This is just my rule, but trans every 50k and diffs every 30k...has served me well over 30+ years and various awd makes/models. Even that is overkill imo.

 

thank you!

 

I drain/fill the transmissions on most all vehicles I service every 30k miles. Not a full fluid swap, just partial drain/fill. This works very well. I decided on that interval from some petroleum engineers on another forum, and based on laboratory used oil analyses.

Diffs are different as you have much less of the contaminants generated in engines and transmissions. If a diff has a clutch-tupe (e.g., Eaton or “Posi-trac” type) limited slip unit in it, I have found 40k to be about the right period - not because the oil is shot, but the limited slip additive. There are geared LSD units out there w/o clutches, but pretty rare. In non-LSD units, I go out to 60k miles w/o issue - including in my GS.