fluid change intervals for manual trans and diff

[delirium330]

My maintenance spreadsheet just alerted me to change my manual trans fluid and differential fluid (currently set at 30k miles or 24 months, whichever comes earlier). In triggered based on the 24 months interval because there is only about 6k miles on both of those fluids (no longer a daily driver).

I'm now questioning the "24 Months" interval as it was established in my younger days when I had more time and energy to get under the car. Also was a preventive maintenance junkie and was driving an e46 ZHP which was extremely cheap and easy to replace the fluids.

Wondering what other's thoughts are on extending my "time" interval since I won't hit any type of mileage interval for awhile. Maybe 36 months... or 48? Car sees spirited weekend driving, no track use, climate mild winters and hot summers in Northern CA.

[dparm]

Originally Posted by delirium330

My maintenance spreadsheet just alerted me to change my manual trans fluid and differential fluid (currently set at 30k miles or 24 months, whichever comes earlier). In triggered based on the 24 months interval because there is only about 6k miles on both of those fluids (no longer a daily driver).

I'm now questioning the "24 Months" interval as it was established in my younger days when I had more time and energy to get under the car. Also was a preventive maintenance junkie and was driving an e46 ZHP which was extremely cheap and easy to replace the fluids.

Wondering what other's thoughts are on extending my "time" interval since I won't hit any type of mileage interval for awhile. Maybe 36 months... or 48? Car sees spirited weekend driving, no track use, climate mild winters and hot summers in Northern CA.

The only way to tell for your exact situation (driving habits, climate, your specific transmission, etc) will be to pull a sample of the fluid and send it for testing. You can easily do this with a hand pump, a short section of hose, and a collection jar from Blackstone -- they even sell the exact hand pump you'd need.

In general, time is not the enemy of transmission fluid.

[admranger]

While both systems are vented and open to the atmosphere, you're probably good at 6k miles with your usage.

Like dparm states, the only way to be sure is to pull a sample and get it analyzed. However, I'd likely just replace everything since the car is in the air and it's not that hard to do. You have to pull the under tray to sample, just like to change. Cheaper and better for the planet to sample and extend the drain interval, but if I'm getting the car up in the air I'm finishing the job (especially now that I have to do it on my back at the new house instead of with my lift at the old house...).

[pbonsalb]

I would not worry with 6k and 2 years. I'd probably go to 4 years since you don't drive the car. Unless those 3k miles per year are on the track.