GM 10 bolt Q's

lone racer

lone racer

Club Member
Hey guys new here on MM,im haveing a hard time figuring whitch way to go,was planning on going with a 8.5 but recently got screwed out of a promise,and besides there pretty exp+ id have to shorten my ds more$$$ ,i have a 7.5 that i broke last year just the ring gear is screwed Thinking about new r&p and a new cover w/girtle and fully welding the tubes,from my understanding with the 7.5 flex is what kills them,my car has no more than 325 HP and around 425 TQ with reg tires no slicks ever. will a 7.5 holdup with above said or am i askin for problems? like every one the money is the issue but i want assurance that im not going to break it again,any insight is appreciated
 
I had a 7.5 in my s10 for 6 years. It had 28 spline moser axles and a richmond 4.10 gear with a SLP posi unit. Pulled tons of 1.4x sixty foots and went 9's @ 140+! Never ANY problems.
 
Another option is using a 3.08 down posi unit with a 3.23 up gear set for that posi unit, the ring gear is alot thicker, a lot less ring gear flex according to the manufacturer. after that, i never had a problem in my s-15, 480 hp 434, tci fmrvb t-400, 2500 stall, 200 shot, even after 80,000+ miles. Also had moser axles. never pulled a 1.4x sixty or went anywhere near 9's though.
 
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8.5" 10 bolts I hear are pretty tough! But you shouldn't have a problem with the 7.5" with that horsepower. Wheel hop is a killer, if starts to do that you better let off...that is what will break it with that amount of horsepower. Just my .02$
 
Maintaining proper pinion bearing preload is one of the biggest problems with the 10bolt 7.5. A solid pinoin bearing spacer is a huge asset in keeping the rear together. I hav a few guys that we have done 10 bolts for that are out and living behind more power then what you have right now.

If you want a qoute to rebuild the exisiting rear end give us a ring

248-682-3840

Sean




lone racer said:
Hey guys new here on MM,im haveing a hard time figuring whitch way to go,was planning on going with a 8.5 but recently got screwed out of a promise,and besides there pretty exp+ id have to shorten my ds more$$$ ,i have a 7.5 that i broke last year just the ring gear is screwed Thinking about new r&p and a new cover w/girtle and fully welding the tubes,from my understanding with the 7.5 flex is what kills them,my car has no more than 325 HP and around 425 TQ with reg tires no slicks ever. will a 7.5 holdup with above said or am i askin for problems? like every one the money is the issue but i want assurance that im not going to break it again,any insight is appreciated
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The g car 7.5 is completly diff than the f car 7.5. Whats your budget for a bolt in g car 8.5 and driveshaft ?
 
Solid pinion spacer for sure.

Once you get the gearset to stay in place, your next problem is the diff or axles. You just can't get big enough hardware in there to make it strong enough.

If you are an automatic on a footbrake, and will have no wheelhop, you can go REALLY fast on a 10 bolt. Stick shift, use the trans brake or have wheelhop just forget about it. That initial or sparattic shock loading just kills them.
 
The 7.5's week spot is the ring gear and the axles, upgrade those and prevent the wheel hop with some suspension upgrades, and you'll be fine at that horsepower level. The 8.5 that you want came in Grand Nationals(and T-types), plus the 84 Hurst/Olds and 85-87 442's. Just keep you eyes and ears open, one will show up eventually, and then you can upgrade to more power.
 
TRBOBUICK said:
They never put a 12 bolt in a g body....
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Well, I thought with the amount of power he was puching it would be enough. We have 8.2 Second Camaro with a 12 bolt.

I have a 6-speed so I bought a Fabbed 9". It takes A LOT of power to bust 9". Prolly 600rwhp or Full spool would hold much more.
 
8.5" rear ends are just as strong as 12 bolts! dave henninger has a 8.5" 10bolt in his 71 z28 and has gone many 8.20s at 160+...
 
1BDTRAM said:
I have a 6-speed so I bought a Fabbed 9". It takes A LOT of power to bust 9". Prolly 600rwhp or Full spool would hold much more.
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At least with a stick shift and heavier cars the diff is the weak link on the 12 bolts and 9"s. For most street and recreational track use there's usually no problems but once you start making more power or becoming more serious you need to go to a spool. Just ask Larry. :lol:

... or go to a Dana 60 ;)
 
SSnthe10s said:
8.5" rear ends are just as strong as 12 bolts! dave henninger has a 8.5" 10bolt in his 71 z28 and has gone many 8.20s at 160+...
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On the 70-81 f car and 84-87 g car 8.5 , the pinion is the same as a 12 bolt. I wouldnt say they are as strong as a 12 bolt.

When they fail , the carrier twists, which binds the ring gear and shears the pinion. The only way a 8.5 will live under a 10.0 or faster car is a spool. And ford bearing ends. Throw at least a 31 spline axle in it, rear end brace and you are done.
 
I just said fuck it and went all out.

Custom Fabbed 9" w/ Back brace
Full spool
35 Spline Axles w/tapered Axle bearings
Richmond 4.30 gears
Strange pro Nodular SC w/ pro Gear bearing
Forged Pinion
Weld in Drag Bar
Wheelie bar mounts
Tow bar


mw-2.jpg


mw-8.jpg
 
1BDTRAM said:
I just said fuck it and went all out.

Custom Fabbed 9" w/ Back brace
Full spool
35 Spline Axles w/tapered Axle bearings
Richmond 4.30 gears
Strange pro Nodular SC w/ pro Gear bearing
Forged Pinion
Weld in Drag Bar
Wheelie bar mounts
Tow bar


mw-2.jpg


mw-8.jpg
Click to expand...

that should do it :lol:
 
Great input,i actually have a 308 carrier (ser 2)w/thick gear (thats chewed up)and plan on using the thick again,and yes the wheel hop is to blame for the breakage,made 13 runs at lapeer, and my friend said it was hopp ppp pppp ping all the way to 3rd ,i could tell because theres a little dip right there and my car was getting loose right when 3rd hit, and my car aint that fast to act like that for sure.A week after that klickity klank.IM alittle more prepared for this year ,have rear sway bar and air bag to help,moneys verry tight like always!i cant and prob never will afford after market stuff just stock type parts,have been working through a temp agency they said this and that ,(were going to hire u in) last week and guess what- LAYED OFF today,:banghead::swear::nopity: tomorows another day and another oppertunity.Any way had 3;42 last year and was floating valves acrost the line thinking about 3;23 this time,should help keep me in my power band alittle better
 
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