I Think this should be a sticky:alot of people on this board ond others always have questions about the gm 7.5.What will fit?What Gears?GM has 2 different splines:26 and 28.28 Was on the 88 or 89 and up years.S-10s are a common swap from junkyards because of the gears and most have posi.A Big misconception is the monte ss all have posi.What can a 7.5 hold up to?Each his own.Some say they have run big-blocks with no problem.Some say they have run 450 hp On a factory rear.Personally I think its only as good as the builder-Throw a motor together without a mic,why did it blow?My point being if your on a limited budget why couldn't the 7.5 work if properly done?my 2 pennys worth
Gm 7.5 10 bolt
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My 78 Malibu had a mild 350 with an old clutch and wouldn't seem to spin the back tires. I'm not sure if it was the clutch or lack of power. I thought the rear was 2.78 posi. The trans was a Vega 4 speed Saginaw with a 3.15 first gear.
I just rebuilt a 400 sbc (Crane 272 cam, Performer RPM, 780 Holley) and installed a new Ram clutch. I got it on the road late in October for some testing before winter. I made a few runs up and down the road in front of house and the engine seemed fine. I stopped in front of the house and brought the revs up to see if the car would spin the tires now. I let the clutch out quick somewhere above 2000 rpm. The 285/40x17s spun around a couple of times and then the car quit rolling under it's own power. The driveshaft was turning, but the car wasn't moving. My son helped me push it back into the garage. The spider gears were split and the metal cage around them mashed. The gears were actually 2.56 posi. I swapped in a 3.42 non posi axle assy. that I had. Now the trans first gear seems too low and I'll probably put in a regular 2.52:1 first gear Saginaw 4 gear that I have. The car is off the road for the winter. I put some 245/60x14's on it take it to the track in the spring. I guess I'm "gun shy". I've got some slicks but afraid to try them now. Maybe it was the tall gears that killed it.
I was also considering putting an automatic THM 350 in it for testing with slicks. I thought it wouldn't hit as hard.
Pete
I Think this should be a sticky:alot of people on this board ond others always have questions about the gm 7.5.What will fit?What Gears?GM has 2 different splines:26 and 28.28 Was on the 88 or 89 and up years.S-10s are a common swap from junkyards because of the gears and most have posi.A Big misconception is the monte ss all have posi.What can a 7.5 hold up to?Each his own.Some say they have run big-blocks with no problem.Some say they have run 450 hp On a factory rear.Personally I think its only as good as the builder-Throw a motor together without a mic,why did it blow?My point being if your on a limited budget why couldn't the 7.5 work if properly done?my 2 pennys worth[/quote]
I just rebuilt a 400 sbc (Crane 272 cam, Performer RPM, 780 Holley) and installed a new Ram clutch. I got it on the road late in October for some testing before winter. I made a few runs up and down the road in front of house and the engine seemed fine. I stopped in front of the house and brought the revs up to see if the car would spin the tires now. I let the clutch out quick somewhere above 2000 rpm. The 285/40x17s spun around a couple of times and then the car quit rolling under it's own power. The driveshaft was turning, but the car wasn't moving. My son helped me push it back into the garage. The spider gears were split and the metal cage around them mashed. The gears were actually 2.56 posi. I swapped in a 3.42 non posi axle assy. that I had. Now the trans first gear seems too low and I'll probably put in a regular 2.52:1 first gear Saginaw 4 gear that I have. The car is off the road for the winter. I put some 245/60x14's on it take it to the track in the spring. I guess I'm "gun shy". I've got some slicks but afraid to try them now. Maybe it was the tall gears that killed it.
I was also considering putting an automatic THM 350 in it for testing with slicks. I thought it wouldn't hit as hard.
Pete
I Think this should be a sticky:alot of people on this board ond others always have questions about the gm 7.5.What will fit?What Gears?GM has 2 different splines:26 and 28.28 Was on the 88 or 89 and up years.S-10s are a common swap from junkyards because of the gears and most have posi.A Big misconception is the monte ss all have posi.What can a 7.5 hold up to?Each his own.Some say they have run big-blocks with no problem.Some say they have run 450 hp On a factory rear.Personally I think its only as good as the builder-Throw a motor together without a mic,why did it blow?My point being if your on a limited budget why couldn't the 7.5 work if properly done?my 2 pennys worth[/quote]
So what years S10 fit the 7.5???? All of them 2 and 4wd??? How do you determine gear ratios on them? I have a couple S10 parts trucks and forgot all about this. Is there anything special I need to do/buy to make it work??? What do you guys suppose or should I say what do you think my 87 monte might have factory (original 4.3 with a 200r4 car)?
midwestls said:
The 82-87 s10's have 26 spline axles, so you can use the carrier and gears. You can use the gears out of 88 and up s10, assuming you have the correct series carrier. Doesn't matter if its a 2wd or 4wd, just remember the axles won't work. I think they use the same spid codes as the g-body cars do as far as determining gear ratios. On a guess i'd say your monte has 2.73 or 3.08 gears.
we had a 7.5 in one of are race cars, mild 355, with about 425 hp, with the bigger bearing kit, and the eaton posi, it held up with no issues but it also cost close to $1000 to build it
im running a 12 bolt, lifting the tires 3 feet with stock axels and no twist
and i think some monte ss' came with a 8.5
im running a 12 bolt, lifting the tires 3 feet with stock axels and no twist
and i think some monte ss' came with a 8.5
Monte SSs did not come with the 8.5. Those were an Olds/Buick deal on the 442/Hurst and Grand Natonal. Pontiac GP Aerocoupes did not have the 8.5 either. Not all MC SS had posi.
Drag Racing Point of View
If your planning on drag racing for any length of time don't waste your money on a 7.5. Sure there are people who make the occasional trip to the strip on a street tire and have some fun, but if you add a sticky tire and a loose converter associated w/around 300 RWHP you'll be pushin that sucker home.
I tried the upgrade thing, Auburn Posi w/ 28 spline axles and blew the spider gears out of it twice. After pushing it on the trailer for the second time it got a Strange S-60 Dana style differential, Overkill YES, will I be pushing it on the trailer because of a busted rear again, Not likely. Just my opinion, I wasted alot of money on a 7.5 when for a few hundred more dollars I could have what I've got now. Good luck whatever you decide.... Peace Out...
If your planning on drag racing for any length of time don't waste your money on a 7.5. Sure there are people who make the occasional trip to the strip on a street tire and have some fun, but if you add a sticky tire and a loose converter associated w/around 300 RWHP you'll be pushin that sucker home.
I tried the upgrade thing, Auburn Posi w/ 28 spline axles and blew the spider gears out of it twice. After pushing it on the trailer for the second time it got a Strange S-60 Dana style differential, Overkill YES, will I be pushing it on the trailer because of a busted rear again, Not likely. Just my opinion, I wasted alot of money on a 7.5 when for a few hundred more dollars I could have what I've got now. Good luck whatever you decide.... Peace Out...
After doing a few weeks of research on this subject and THEN running into this thread Id like to give my 2 cents. I have been running the standard chevy 10 bolt 7.5 open since 1996, they are junk unless you put hundreds if not thousands in them. Like busdriver said, if your pushing more than 300 hp at the tire your pushing it home.
The only decent 7.5 rear end came in the ss monty. It was a limited slip unlike the rest of the G Bodies. It was a little better at holding H.P. but not as good as the infamous Grand National 10 bolt. From 84 to 87 they pumped out these rear ends, most at a 3.42 ratio. The Hurst Olds and the Olds 442 came with the same 8.5 inch and are all hot swapable. I have an 80 ss Elky and just purchased a G.N. rear end. It was not easy to find and it was not cheap but I guarantee that 10 bolt will outlast any 7.5 open hands down. BTW, I'm selling that 10 bolt real cheap, it has fresh oil and I'm in N.C. 🙂
Darrin
The only decent 7.5 rear end came in the ss monty. It was a limited slip unlike the rest of the G Bodies. It was a little better at holding H.P. but not as good as the infamous Grand National 10 bolt. From 84 to 87 they pumped out these rear ends, most at a 3.42 ratio. The Hurst Olds and the Olds 442 came with the same 8.5 inch and are all hot swapable. I have an 80 ss Elky and just purchased a G.N. rear end. It was not easy to find and it was not cheap but I guarantee that 10 bolt will outlast any 7.5 open hands down. BTW, I'm selling that 10 bolt real cheap, it has fresh oil and I'm in N.C. 🙂
Darrin
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