Help with rear end identification

[naminator]

Alright. So it is a 1978 Grand Prix SJ, with a 5a motor, either vin y or vin 9. It is parked close to my neighbors trailer and on a real cheap asphalt, so I am not moving/jacking it up until I am at the point I want to get under it. Unfortunately a large concrete curb stop and fence, prevent me getting right inbehind it and a recent brake issue makes me hesistant to move it around (the passenger tires are both leaking).

Anyways the car has some odities about it. Trans am rims, a 307 rocket v8, a very custom scavenged sound system and had straight pipes. It looks like dual exhaust, but until its mobile I cant really see under that side with the 2 catch pans under the million leaking spots. So I was trying to get a look at the rear end, and snapped the following photos. I do plan on replacing the oil in the diff, but thats down the line. Is this an 8.5 10 bolt? If it is an oldsmobile 8.5 it fills in the picture even more.

 

[oldsmobile joe]

no that is not an 8.5" rear axle. that is a 7.5" rear axle with a '78 rear sway bar attached. most likely the original rear.

 

[Steve 82 Elly]

I agree with Joe, looks like a 7.5" to me too.

 

[69hurstolds]

It's not an 8.5. Otherwise it would have triangle shapes at 5 and 7 o'clock positions. That one has fangs. Thus- 7.5". Probably the original rear.

 

[naminator]

Well good to know. I really am not too torn up, the car has a lot of weird things. I will for sure get a much better picture, with measurements, once I fix the brake line and can pull it forward. The combo of fence, curb stop and a very frustrated colony of pavement ants made me less than excited to climb under the rear of the car.

 

[79 USA 1]

Quick guide for reference.

 

[ck1984]

so its agreed , its not an 8.5
off topic but my cutlass came with dual red bottle glasspaks that sounded TOO LOUD AND TERRIBLE when they dumped underneath the back seat.
i was changing the anemic 305 to an LS anyways so i never fixed that exhaust,
but in middle of building my LS swap, i dumped a single 3 inch under the same back seat area and it was ALSO TOO LOUD and almost AS TERRIBLE sounding as b4
BUT just dumping, that exact same exhaust out the side made all the difference in tone and amt of sound in the cab. it now sounds great in comparison
[it may still be too loud enough to eventually get me a ticket but at least in the cab you can carry on a conversation unless under full throttle]

 

[ck80]

May not be trans am rims either.

If you're seeing "snowflake" style Pontiac rims you should know that the grand prix of those years had a factory option for rims that were a similar "snowflake" design appearance, but the rim size and offset were different than the fbody firebird/trans am ones.

 

[naminator]

so its agreed , its not an 8.5
off topic but my cutlass came with dual red bottle glasspaks that sounded TOO LOUD AND TERRIBLE when they dumped underneath the back seat.
i was changing the anemic 305 to an LS anyways so i never fixed that exhaust,
but in middle of building my LS swap, i dumped a single 3 inch under the same back seat area and it was ALSO TOO LOUD and almost AS TERRIBLE sounding as b4
BUT just dumping, that exact same exhaust out the side made all the difference in tone and amt of sound in the cab. it now sounds great in comparison
[it may still be too loud enough to eventually get me a ticket but at least in the cab you can carry on a conversation unless under full throttle]

I don't like the current setup. Once I finish fighting off a bleeder valve that sheared, I am hoping I can move the car around a bit. Then I will be changing the diff oil, trans pan gaskets and some other things. It has true dual exhaust and is dumping under the car, which I dislike. My goal is to route the exhaust out the sides, behind the rear tires, but not high on the priority list.

May not be trans am rims either.

If you're seeing "snowflake" style Pontiac rims you should know that the grand prix of those years had a factory option for rims that were a similar "snowflake" design appearance, but the rim size and offset were different than the fbody firebird/trans am ones.

I posted them somewhere else on the forum, but I am 99% sure they are trans am rims. They are those WS6/Turbo whatever they are rims with the slats, not the snow flake (which I would have preferred). The passenger tires are pretty much flat 2-3 days after filling them, so if the tires are shot I might just get different rims, otherwise my plan is to remove the flaking clear coat then polish them heavily, and if the pitting/damage is too bad, paint them/plastidip them.

 

[oldsmobile joe]

These?