Front/Rear/Transfer Case service question

Trying to see if its recommended to service/change my front/rear/transfer case differential oil or not. Last time I did these 3 was at 50000 miles. I currently have 109000 on my 2002 Tacoma. I don't tow nor had I ever did before. Not sure if these service should be kept up regularly or not like an oil change. I know any oil will breakdown over time. Just trying to do some preventative maintenance while I have some time off work. Thanks.

 

I check mine twice a year, if it looks really nasty, I change it, if not keep driving!

 

Okay I'll check it and see how the fluid is and go from there.

 

Change the rear diff oil for sure. You are way over the 30k interval already. Rear diff sees a severe heat cycle every time you drive, so the oil breaks down faster. You know the rule of thumb where rwhp is about 20% less than flywheel hp due to driveline losses? About 15% is lost in the rear diff due to high friction in the hypoid ring-&-pinion gearset. At full throttle, 15% of 190 hp is 28 hp -> 21,000W heat being dumped into the oil... which does not have a filter or a radiator.