I have read that the 1-2-1 shift applies the OD band when you do this, which is not supposed to be good.
However I made over 150 passes in a 3600lb cougar, 4.10's, shift kit with 260000 on the odometer(Don't know if the tranny was original, probably second one). This was done on street tires with times from low 15's to low 14's. Never had a problem personally.
Hold first to your shift point.(mine was 5000 on one cam and 5500 on the other). Shift to "D" then right back to first. Hold first till second gets to your shift point. Then shift to third.
To the people who hit first. I think what happened was that when you did the 1-D-1 thing, the RPM's were not high enough when you did it. It will go back to first if the RPM's are not high enough, but will lock first out if they are high enough. Other than that mabey a tranny problem. I still have my tranny, works great. Just now I like a stick.
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82 Mercury Capri 302.
Comp. Cams
Tremec 3550
3.73's
12.8@106 N/A