I want to put posi and 3.73 gears in my 91 RS. Is this an easier proposition than just swapping out for a 4th gen rear? Cost seems to be about the same, a couple hundred for gears and a couple hundred for posi, and the 4th gen rears go for 400-500 usually(and have at best a 3.42).

I have absolutely no experience working on rear ends(that sounds really perverted doesnt it!), but I am and average skilled mechanic. I can replace struts and springs, do heads and valve lash etc. I dont have a garage anymore so I'm wondering if i can swap gears and diff fairly easily or what.

Also, I know that the housing is diff. in the cars that have 3.08 and up gears, so I'm supposed to run a "thick" gear or something?

 

Swapping a complete rear is easier than installing new gears.

 

I could get a 4th gen rear with 3.73's and disc brakes for 500 from Hawks in SC. Is that a decent price or should I scour the forums for one cheaper?

 

I would be carefull there, no 4th gen car came stock with 3:73 only 2:73 gears. Let the buyer beware.

 

There's no advantage of a 4th gen diff compared to your 91 except maybe a different brake system. There's actually a disadvantage of having longer axles which means you'll need rims with a different offset.

Installing a posi and new gears isn't hard however for the average backyard mechanic with no knowledge of what needs to be done or doesn't have special tools, you're better off having a driveline shop install them.

 

They give you the option of a bunch of diff. ratios, so I think they must change them out.

How much do you guys think a shop would charge to install a diff and gears? And do I need a spacer for my ring gear or a thicker gear or something?

 

Usually you can bank on paying the mechanic about as much as the parts he's installing, especially if you didn't buy the parts from him. It would be easy for you to call a few places and get a quote.