[pena0724]

Hi guy's i have a gm 10 bolt 7.5 rear end in my 87 cutlass i believe the gr is 2.13 because the gears are marked 22.47 i want to switch to a 3.73 or 3.42 my friend gave me # 3 carrier Richmond posi unit which had 3.73 gears i was told i need to go with the thicker gears is this so and if so why? my question to every one is should i go with 3.42 or 3.73 I would like to do some highway driving but i want a good kick off the line this is what i have 350 turbo 3,000-3,500 stall 355 Chevy alum heads.

 

[fast68]

2.21 2.28 2.56 2.73 2.93 3.08 are the ratios it can be if its stock factory highway common smogger car ratio still

3.42 would be about as deep as i would go if you plan on alot og highway driving rather than in town driving

its not gonna be real good on fuel mileage anyways with how its built, so i wouldnt be so worried

or put in a 2004r trans and then 4.11 axle or so,

 

[ericnova72]

Are you sure it is a 3-series carrier?? Only the 2-series carrier would require you to need a thick gear for the 3.42 or 3.73 gear set.