I have an 88 TA with a 700r4 and 2.73 gears. My question is, what do I have to change to install 3.73 gears and a posi. BTW, this is the most informative forum that I have found. Thank you.

 

buy a gear set and a install kit total about 300 dollars. if you look in a catalog you'll see same ratios one will say for x:xx and numerically lower gear carriers and the other will be for y:yy and numerically higher carriers. the differance is the thickness of the ring gear. to swap it i'd remove the rear end and do it on a bench.
swap in the pinion and shim, most or all will need .035 shim
set pinion depth with a depth mike
install crush sleeve and set bearing preload
install ring gear and carrier
set back lash
check contact pattern

not hard to do but requires tools most people don't have. i have a set of gm 3:73 gears i'd sell for 75 dollars plus shipping ede@nethirdgen.org