Re: question, G body 7.5 rear life
 

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!

Re: question, G body 7.5 rear life
 

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.

Re: question, G body 7.5 rear life
 

Finding a Grand National housing is proving to be rather difficult. I know because i am looking for one to put in a Malibu Wagon.

Re: question, G body 7.5 rear life
 

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.

Re: question, G body 7.5 rear life
 

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.

Re: question, G body 7.5 rear life
 

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.

Re: question, G body 7.5 rear life
 

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

Re: question, G body 7.5 rear life
 

Friend of mine has a 87 Grand National rear end for sale, 3.90 gear TA Cover, stock axles, good drum brakes. He is In Illinois, but will be going to SGMP in a couple weeks for ducks race. He can deliver between Illinois and SGMP $1,600 obo

Re: question, G body 7.5 rear life
 

Man,I hope not! In the 70's when I worked on the line at the Chevy dealer, the Vega had a ring and pinion pitch noise(howl) at about 30-35 MPH. You could adjust pinion depth, experiment with back lash, do whatever you want, but that rear end was going to howl. We were so glad as more and more Vegas went beyond warranty because we knew people weren't going to spend money on a Vega to fix it. We never really came up with a real fix for that unit, it just seemed to be a real poorly machined piece. Quality control was nonexistent anyway on those cars. Also, when the Chevette came out in 1976, every last one you would ever drive had a pitch noise that would come in at 40 MPH. You didn't need the speedometer to tell when you hit 40, the rear axle assembly would tell you. Also, full sized vans did that, too, although trucks wouldn't even though they had the same rear end assembly. Later on, it dawned on some of us that the Vega, the vans and the Chevette all were unit body with the rear end bolted to a unit body. It was possible that setup transmitted a normal noise to the passenger compartment that the separate frame and body with mounting bushings somehow isolated it. I was nervous about smaller rear ends not only from the strength standpoint, but wondered if the noise came from poorly machined or mismatched parts somehow.

Re: question, G body 7.5 rear life
 

You are right Greg the G Vans were horrible with rear end howling new or used years ago ive had race car rear ends that didnt howl as bad as them. going back to the original question go ahead and buy the good stuff now for a 12 bolt and then no worries.




Jerry
Retired 3490 3492 STK SS SST