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Transmission fluid service interval

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The owner's manual says to replace the transmission fluid every 150,000 miles. The Boss 302 supplement makes no mention of a different interval. What interval would the forum suggest for a DD that goes to the track 7-8 times per year? Does shift quality degrade as the fluid ages, or does the fluid work to spec until it fails?
I change it annually as well. I have never noticed a change in shifting due to fluid degradation (I thought I was once, but turned out to be clutch failure). I've been using BG synchro shift II with good results as a year round weekend car with 5-7 track weekends in the summer.


Lord knows I'm a Voodoo Child
Exp. Type
W2W Racing
Exp. Level
10-20 Years
Cookeville TN
Depends on how hard you push on track but 7 days plus DD should be OK for annual change. If you do 7 weekends (14 days) then you should chage every 7 track days. Street driving does nothing to the fluid, temps rarely exceed 150 degrees, track driving at high speed and high rpm downshifting sees the temps skyrocket to 280+ degrees, this kills the fluid and puts many more contaminents in the fluid from synchro wear. I run a trans cooler setup and change every 8 hours on track.
Boss 302S recommendation is every 4 hours for both Trans & Diff Fluids. I agree with Steve, sustained hard driving raises both Diff and Trans temps. I am changing both fluids at 4-8 hour intervals based on ambient temps and session duration (30 minute sessions drive noticeably higher temps than 20 minutes).

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