I am considering changing the rear differential in my 84 300SD from 3.07 to 2.47. I read the threads here with great interest and learned a lot, but have some unanswered questions. I am interested in hearing follow-up from people who have made this modification:

1. Gas mileage - how much, if any, did your mileage improve with the 2.47 differential.
2. Installation - I know you need to remove the halfshafts from the diff, but do you need to remove the halfshafts from the wheel hubs?
3. Installation, part II - Can one simply unbolt the flex disc from the diff, or does the 'gland nut' on the driveshaft need to be loosened (that's the procedure according to the FSM).

I am most concerned about increasing the mileage. I am currently averaging 26mpg, but would like to increase that. On a recent 1600 mile road trip at 65-75mph, I averaged 22-24mpg.