I'm looking for a new rear, I know of a S60 for sale with 4.56's in it. My car is all stock for now except for the STS kit. What gears should I be looking at, my car sees very little track time, and is mostly driven, cruised, with some occasional stop light races, and messing around. When I do go to the track I want something I'm going to have fun with also. So what ratio should I be looking at.

 

Somewhere around 3.23 depending what size tire you run at the track. 2.73 will be a beast on the streets or 3.08 depending what gear options you have for the type of rear end.

 

4.56 are no good for the turbo way way too high.And that used rear end is a locker I think..not that streetable. You would want a tru trak not locker or spool. Especially if you do a lot of street driving and the tru trak should take big power thru an auto to cushion the shock.

I am also going with dana 60 but 3.54 gears thats the lowest you can get in a dana you can't get 3.08 or 3.23 or 2.73.

I am maybe in a bit of minority here as many turbo guys like Outlaw like the lower gearse 3.23 and less with turbos but I don't. I like 3.54 or even 3.73 with autos even with turbos and especially because I am driving mostly around town and can't stand the doggy feeling of a 3.08 or 2.73 the 3.23 woulb bel lowest I can go personally but again the dana 60 don't have that option. Off boost 3.54 or 3.73 are nice and snappy and seen many many turbo cars running excellent very fast times with 3.73 even some with 4.10s.
A lot depends on what you want to go thru the traps without having to go to overdrive and your top speed needs. And of course tire height can be played with too and affects the two previous things.

With my redline of 7000 max and 3.54 I think will have enough mph for me and more than enough top speed for any sane person. Some say the lower gears spool up the turbos faster. Well they spool plenty fast enough for me with my current 10 bolt 3.42 and see no proof that the lower gears are better even in the 1/4 mile as long as the car didn't run out of rpm or have to shift to overdrive.

There used to be these things called boosted lists and they are still there if you do a search for like boosted list 2006. They are not the same as the sticky at the top.They show many many combos and times and you can see what other guys run. I was surprised how many are running 3.73 or even 4.10 with turbos.
Local buddy has 3.73 with his sts rear mount but its a m6 . He is very happy with them around town,off boost and on the highway was well. His trubo still spools up really quick.quck enough to spin the tires easily .He don't have nittos but some high end street tires.
I run nittos.

The price on that rear end is not that great compared to new price and new you can pick the 3.54 or 3.73 and the tru trak .But would stay away from spool or locker. YMMV.

 

I ran a 3.73 for the longest time then about a year and a half ago I switched to a 3.23. the car is great for cruising 70 mph around 2000 rpm. But I like to race it when I can. so I have been throwing around going to a 3.42. pick up a little on the bottom end and not lose all the top end.

by the way the car ran 11.5 @128 on a 2.0 60ft