Is the tranny a side-loader? I've mostly dealt with my '68 3 speed tranny. The shift arm coming out of the tranny is splined, which is eclosed by a clamp. The clamp connects to the shift linkage. On my '68 the clamp was loose and didn't engage 3rd gear completely, so it would pop out. How often does it pop out of gear? It also could be caused by too much endplay in the input shaft. Also, check your motor mounts for wear.
On the Metro. Does it make any odd sounds when you try to downshift, like grinding etc.? How many gears do you have? If it only going from 3-2 then from 2-1? Hope this helps some. John.
1968 Chevy C-10, 250 and 3 speed on floor, Hedman headers, Offy intake, Edelbrock 600cfm 4 barrel, HEI
1966 Chevy C-10, motor and tranny went into the '68. Waiting to be restored.
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