Possible reason for shearing 3rd/5th gear?
I had a hunch on why 3rd gear (and sometimes 5th) seems to like to shear off on GSL-SE's when you go to a puck clutch. I looked at Felix Miata's comprehensive list of the gears used in various Mazda transmissions and this is what I found:
(stolen from http://mrmazda.members.atlantic.net/tranchrt.txt )
Code:
20:55 Rear Net Tire RPM @ -Countershaft & Mainshaft Gear Teeth--
Vehicle Year 1st 2nd 3rd 4th 5th Axle Final Tire Size RPM 60 MPH C1 C2 C3 C4 C5 M1 M2 M3 M4 M5
RX-7 79-83 3.674 2.218 1.433 1.000 0.825 3.909 3.227 185/70-13 892 2878 13 20 25 29 31 28 26 21 17 15
RX-7 GSL-SE 84 3.622 2.186 1.419 1.000 0.758 4.083 3.097 205/60-14 878 2719 13 20 32 37 51 28 26 27 22 23
RX-7 84p 3.622 2.186 1.419 1.000 0.807 3.933 3.175 185/70-13 892 2832 13 20 32 37 50 28 26 27 22 24
RX-7 85 3.622 2.186 1.419 1.000 0.807 3.909 3.156 185/70-13 892 2815 13 20 32 37 50 28 26 27 22 24
RX-7 GSL-SE 85 3.622 2.186 1.419 1.000 0.715 4.077 2.914 205/60-14 851 2480 13 20 32 37 40 28 26 27 22 17
Note that in '84 Mazda went to a different 3rd gear with finer teeth, and 5th gear teeth went finer as well. I wonder if it would be advantageous to use '81-83 transmissions for high powered (or well-abused) FB applications for the stronger, coarser gears in 3rd and 5th. Supposedly (haven't had them apart) they went to larger bearings in '83 for durability, so the '83 transmission is possibly the BEST one to use.
Armed with this knowledge, I might swap my '80 trans in the '85 after all! |
