I burned out my motor. overgeared?

[Trike]

I went out for my 2nd race with my Z-car conversion on saturday. Had a great day, Made 3rd in the B-main and got bumped up to the A main. 15mins into it, the motor seized.

my setup.
Medusa 30-60-1600
Gearing: 15/44
MMM ESC
6s 2650mah 20-30c

To start off, I knew it was running a little warm during the qualifying rounds, the motor hit 160F, the ESC hit 160F'ish, battery was 98F. During my 20min main, I came in to change the battery at around 10mins. The ESC wouldn't re-arm, I think it overheated/thermaled. Took about two mins to re-arm. After the race, I ran back to my table and temped the motor. 216F . The ESC was at 168F, battery was at 98F. I knew the motor was done for. But figured I run it during the A-main anyways, it finally seized 15mins into it.

During the qualifying rounds, I changed the timing to its lowest and moved the throttle curve a lower, hoping it would help a bit during the main.

During my 1st race a month ago, I never had any temp issues.

This is what changed since the first race.
Rebuilt diffs with heavier oil 5-7-3. The center and front had leaked out.

ESC settings:
Punch control set to 100%
drag brake set to 20%
Timing set to low.
start power set to low.

The only thing I can think of that may have caused it is the heavier diff oils, and the drag brake set to 20%. That combined with more consistent lap times may have caused it.

So.... What could I have done to fix this? Smaller pinion?
The next question would be. I still have my 6s packs. Should I stick with the medusa 1600kv so I can continue to use them?

Thanks! This has been a good learning experience for me and its been fun to tinker and to see how the changes affect the performance.

Thanks!