When I did mine in my 90 I just unbolted it and pulled it out as far as I could to access the shaft bolt. just don't lose it down in the cowl

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I also had to make sure the replacement was stopped in the same position as if it it is not the wipers will seem to stop in the middle of the windoe (which mine did exactly that

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I then had to pull the motor back out and move the shaft mount aa couple of teeth till my testing it showed the proper stop position..
Good Luck...REMEMBER....Don't drop the bolt....