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In my case it seems that 3rd gear separated enough to keep 4th from spinning freely. Pressed back together to close the gap and all is well. There is a suggestion to tack the two pieces together, though some questions remain for me:
Where to tack? See pictures, my thought -- see red asterisk
Do you tack a second time, 180* opposite, to "balance" the slight amount of added weight?
Do you do both 3rd and 4th because they're of the same two-piece press together nature?
This is going in my "rods only" VVT/6258 build. Thanks in advance.
The asterisk in your picture is on a split shim, you don't want to weld that. The part that can separate in 4th gear is the synchro cone / dog teeth and the helical gear (red line in the picture below)
The newer miata 6 speed comes with welded gear from factory. The top gear in the picture if from an older 6 speed and you can see the the cone / dog teeth is simply pressed on the helical gear. The lower one come from a newer 6 speed and you can see that it has been welded all around
Excellent info, thanks. I didn't know the later trans had the gears welded already -- any idea if the cutoff of the gear revision is the same as when they modified the shifter?
For now, I do have a "late" 6 speed transmission in the car.
We haven't done the welding on the "early" transmission yet, but thanks for confirming my picture is wrong. The innards are new to me.