question, G body 7.5 rear life

[SSDiv6]

Originally Posted by Ralph A Powell

Oldsmobile had a bolt in 12 for the G-boy racers. There are a few around if you know where to look.

None of the factory issued Oldsmobile Stock Eliminator cars had 12-Bolts in the cars. They all had 8.5 rear ends. Later on, a few switched to aftermarket 12-Bolt rear ends.

[Ralph A Powell]

Originally Posted by SSDiv6

None of the factory issued Oldsmobile Stock Eliminator cars had 12-Bolts in the cars. They all had 8.5 rear ends. Later on, a few switched to aftermarket 12-Bolt rear ends.

All came with the 7.5 rear But when I was at Oldsmobile I wrote the purchase order to have 125 made for the Old g body as produced they had the correct brackets for a true bolt in. We never sold them but they were given out to the racers through Oldsmobile Special Vehicle Operations!

Where are they today God only knows. A lot of the racers got 2. You just going to contact old Olds racers and see if they might have stashed one!

[Greg Reimer 7376]

Seems to me that the 7.5" rear end was a V-6 rear end that came out in the mid '70's when everything got downsized and cheapened to the point of near extinction. The 8.5" rear end came along in the 72 model year in a few cars, it replaced the 8.2" 10 bolt and the 12 bolt, but by '73 or so, nothing made enough horsepower to break it anyway. The 8.5 would probably hold up if you put steel web caps in it, the right hardness gears, of which there are not anywhere near the ratios available that the 12 bolt has to offer, a good spool, proper axles, and by the time you did this, you might as well have bought an aftermarket 12 bolt housing that's right for the car. This is a clear cut case of paying to do it right and paying only once. The Buick GranSport turbo cars had the 8.5, but the turbo cars didn't leave nearly as hard as a small block stocker will, they made up for it with boost down the track a ways.

[SSDiv6]

Originally Posted by Greg Reimer 7376

Seems to me that the 7.5" rear end was a V-6 rear end that came out in the mid '70's when everything got downsized and cheapened to the point of near extinction. The 8.5" rear end came along in the 72 model year in a few cars, it replaced the 8.2" 10 bolt and the 12 bolt, but by '73 or so, nothing made enough horsepower to break it anyway. The 8.5 would probably hold up if you put steel web caps in it, the right hardness gears, of which there are not anywhere near the ratios available that the 12 bolt has to offer, a good spool, proper axles, and by the time you did this, you might as well have bought an aftermarket 12 bolt housing that's right for the car. This is a clear cut case of paying to do it right and paying only once. The Buick GranSport turbo cars had the 8.5, but the turbo cars didn't leave nearly as hard as a small block stocker will, they made up for it with boost down the track a ways.

There are a lot of GM Heavy Stock Eliminator cars running the 8.5 rear end with no problems. Replace the cap bolts with ARP studs, use a solid pinion spacer with shims in lieu of the factory collapsible/crush spacer and put the girdle rear cover and you are good to go.

[Adger Smith]

Back in the IHRA days I had a customer that ran a Crate 385 in a Malibu wagon. The 7.5 would last about 50-70 runs and spit out the pinion or take teeth off the ring gear. That was with a good spool, caps and axels. Went to the 8.5 and the ring and pinion problems stopped. As a by product he was able to get better brakes on it, too.

[Bernhard]

https://gbodyforum.com/threads/86-44...ear-end.79216/
This is not my diff.
I have had good luck sourcing parts from car specific forums.
1500 US seems high but that may be the current rate.

[Lyn Smith]

Isn't a 7.5 rear end the same rear end they put in Vegas in the 70s?