question, G body 7.5 rear life
 

In a G body stocker weighing about 3200 with a 305 stocker package, running low 12's high 11's

Will the 7.5 gear give any service life?

Re: question, G body 7.5 rear life
 

50ft or 50 seconds which ever comes first! Spend the money once and put in a 12 bolt. Several manufactures offer a complete bolt in.

Re: question, G body 7.5 rear life
 

If you are making decent horsepower and the suspension is up to the job,the 7.5 won't hold up. I thought a Grand National 8.5 would do the trick ;that piece failed after a few seasons .The answer is to do it right the first time with a 12 bolt and pro gears.

Re: question, G body 7.5 rear life
 

Yes to all above. Had a Firebird. It ran 13.60 and boom oatmeal in the rear end housing

Re: question, G body 7.5 rear life
 

Axles and internal parts are all about the same money, save for the extra cost of pro gears. Put the best unit in it that you can from the beginning.

Re: question, G body 7.5 rear life
 

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

Re: question, G body 7.5 rear life
 

I give up ... Where do you look?

Re: question, G body 7.5 rear life
 

News to me. Any more details?

Re: question, G body 7.5 rear life
 

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.

Re: question, G body 7.5 rear life
 

Find a 8.5 from a Grand National or 1984 to 1987 Olds 442 or an aftermarket 12-Bolt.

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

Re: question, G body 7.5 rear life
 

Where or Who do you guys recommend for a 12 bolt replacement? Moser/Strange? Thinking of ordering a bolt in 12 bolt for a 4th Gen Camaro... I'm thinking it would be best to just order the whole ball of wax at one time..

Re: question, G body 7.5 rear life
 

Double check when ordering. We shopped around and told every person that was selling Moser what exactly we wanted. One company was cheaper so we went with them. Come to find out after we received unit some items we requested were not on housing assembly. ( NOT Moser fault)Complained and showed exactly what we told them. They said we paid for what we received. So we had to order the other items to make it 100% ready to bolt in. I think it was no studs, wrong axle bearings, and something else.
It was for a 78 Camaro. Went in car with no problem. Everything fit well.

Re: question, G body 7.5 rear life
 

[QUOTE=Jerry Terry;625161]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.

The G-van rear axle howl was always kinda figured to be attributable to the fact that the operator was driving a huge "speaker" down the road. Or maybe better referred-to as a megaphone. Pickups probably had noise too, but you just couldn't hear it in the cab.

Re: question, G body 7.5 rear life
 

[QUOTE=nhramnl;625230]The pick up had a separate body/frame construction so any noises created by a ring and pinion wouldn't have transferred through the body bushings between the frame and the cab. All the cars that were notorious for rear end noise were unit body as well. The van rear end and the truck were the same at that time(mid-late '70's, ) and they held up pretty well, but there could have been a lapse in the quality of the set ups. I don't know how they initially set up rear ends at the factory, but it could have needed some design engineering. My late aunt from decades ago bought a new 64 Nova wagon with a 283, a Glide and power steering and brakes. It was the first year for the 283 in the Nova and the first 10 bolt 8.20 rear end. It had a rear end howl at some speeds as well, and Novas had leaf springs attached to the unit body like the vans did. I don't remember anybody telling me that Chevelles of that era had that problem, but Chevelles always had a full frame. The Nova she had came out about 10 years prior to my entry into the world of car repairs and service. i did wish at one time I had the original block out of that car!!

Re: question, G body 7.5 rear life
 

This isn't directly related but when I built the Pacer I put a V8 AMC 20 rear end in it, 8 7/8 ring gear. Thinking putting the original 6 cylinder rear end in it would pick it up, I put together an AMC 15 (Dana 35) with the 7 9/16 ring gear. Results were I didn't see any improvement in the et. I haven't broken the Dana 35 but I didn't see any gain. Same ratio in both cases.

Jim Mantle V/SA 6632

Re: question, G body 7.5 rear life
 

Yes, we run 10s with one, but its all setup real well.