im goin hunting in the junk yard for 9bolt 3 series carriers because the price of a new one is beyond expensive.

how will i be able to tell what gears are in the rear? will the RPO be an indicator? G80 is the 2.77 gear so thats out.
is G92 all the same gears? or were here different gears avaible?

 

Finding a 3-series 9-bolt carrier in a boneyard is next to impossible. Most 350 tpi cars with a auto had 2:77's wih 1989 having 3:27's as a option, again very few. Also a handful of 305 tpi 5-sp ones had 3:45's. RPO G-92.

The RPO code G-80 is for a limited slip axle and not for gear ratios.

Anyways, unless you are really lucky finding a intact 20yr old 3rd Gen with a 9-bolt rear is like finding a winning lottery ticket.

 

pulling the cover is about the only way to know the ratio

 

While a 9 bolt is a bit stronger than a 10 bolt, it is much easier and cheaper to get parts for a 10 bolt. IE: Gears, Eaton plate style Posi's, Torsen diff's, PBR rear disc brakes (Edit: Beware if brakes have been removed. Brake mounting brackets for 9 bolts are extremely hard to find. Different shape than 10 bolts )...etc.

You might want to reconsider your choice.

 

As far as identifying the ratio, pulling the cover is the only sure fire method to tell. But the G92 option usually designates 3.27 or 3.45 ratio as a rule of thumb. As far as the brake mounting plates, we were able to modify the ten bolt disc mounting plates on my buddy's pbr brakes to work on the nine bolt by routering out the mounting holes slightly to line up with the nine bolt axle flange. Chickenman is right about finding the original nine bolt disc plates, they are extremely hard to come by. But I know for a fact that you can modify the ten bolt pbr plates to work just fine on the nine bolt. I have to agree that the ten bolt rears are much more user friendly when it comes to changing ratios and using different posi carriers, etc.

 

all im concerned with is the carrier, i have an 89 9bolt with disc brakes, im looking for the carrier because i want to go with a numarically higher gear then the current 2.77's i have now.

i know the G80 is for axel but every g80 third gen i have seen are geared 2.77. and isnt G92 a package deal? duel cats, and better gears, and a few other things?

 

Yeah G92 option is a package deal. On 90-92 cars, the G92 option did include dual cats, better gear ratio, and 4 wheel disc brakes. Unfortunately, like the other guys said, finding a 3 series nine bolt carrier in the junkyards is very hard to do. Your best bet would be to do a search on the classifieds here or check good old ebay to try to find the 3 series carrier. I don't see them for sale very often, but every once in a while, I do see them for sale for fairly reasonable prices.