GN rear

[m.$terner]

-not quite sure where to ask this so thought id give it a shot in general tech. looking to do a build soon, most likely with an el camino. i have a motor already. loooking to probablly pick up a 200r4 and now my question is the rear. before i start shopping for a rear i want to know what i need to be looking at. i want to put a turbo buick rear under the car. however when i go to look at rears from a private owner how can i tell the difference betwen a GN rear and a regular gbody 10 bolt rear? im assuming the numbers on the rear decide that.if anyone could give me some help here about what i need to look for please let me know. just do not want to end up spending big money on what i think is a GN rear and in reality is a regular old 10 bolt GM rear. thanks

 

[novaderrik]

look at the covers and the bottom of the housing.
a regular 7.5 has a small oblong cover and a rounded bottom on the housing, and the 8.5 has a bigger round cover with a pair of triangular "ears" on the bottom.
both covers have 10 bolts.
the 8.5 was only used in 84-87 turbocharged Regals- GN, T Type, etc- and 84-87 Olds Hurst/Olds and 442 versions of the Cutlass. the Buick rears had 3.42 gears, and the Olds rears had 3.73 gears.
every other 78-88 G body had a 7.5" rear axle.

if you do find an 8.5 housing and aren't sure if it's a G body rear, just look at the ends of the axle tubes. everything else that got the 8.5 had the brake backing plate bolted on with 4 bolts and a brake wheel cylinder held on by 2 small bolts, and the G body had the weird flange with one big bolt and had the wheel cylinder held in with a clip.
look for the weird flange with the clip and it is a g body rear end- nothing else will bolt in.

but....

last summer, i had my 74 Monte Carlo and my 84 T Type parked next to each other in the garage.. so i jacked both of them up and did some measuring on the rear ends. the mounting points for the lower control arms are in about the same spot, and a person MIGHT be able to make some sort of a bolt on adapter to put the g body upper mounting points on the older rear.. i think the spring perches and shock mounts were also pretty close, too..

this would make it really easy to find a donor 8.5 without spending the money for a GN housing- just find a 73-77 A body or 77-96 B body and get the rear end out of that. of course, that rear was about 3" wider over all- which would work perfect if you had a complete set (2 fronts, 2 rears) of GTA wheels and wanted to use all 4 of them on the car. it would also open up a whole bunch of options for bolt on junkyard rear disc brake setups..

 

[m.$terner]

Thank you novaderrik, that is exactly the info i was looking for. i actually have what i believe is a GN rear as well as two other 10 bolts (7.5 im guessing). If this is the case then i will most likely end up using the rear if is it in fact a GN rear. if not though I would deff be interested in checkiing out your other option as i do have a set of gta wheels i was hoping to maybe use on this project. i think a all blacked out el camino with black gta wheels and a 350/200r4 with a 8.5 GN rear would be a decent build. Te hard part is going to be finding a decent shape el camino body. i also have the GN header panel and grill, would love to put that on it but i was reading about the guy who did that before and he said he had to graph the fenders on and all,not looking to do an extreme build here, just a nice cruiser on a reasonable budget. thanks for the help though.