I don't think that there is as far as strength goes (someone in another post said there wasn't) but I just need to make sure......
bsa

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"If they do not run, Then they will die." - Stonewall Jackson

'87 IROC, 355 TPI,700R4, Trick Flow Heads, Comp Cam, Comp 1.6 Rockers, Lucas 23# injectors, Edelbrock headers, Flowmaster 3'' exhaust, gutted cat,
Mallory coil, Mallory HyFire IV ignition box, Mallory Sidewinder 8mm wires, Autolite platinum plugs, K&N filters, Transgo Performance Shift Kit, Corvette Servo, 2,000 Torque Converter

 

none

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91 RS W/carbed 350, Vortec heads, performer rpm, Comp cams Xtreme energy 280 grind. BFG Drag radials. 3.42 posi,Corvette servoed 700r4, ****ty stock converter
13.24@104

 

Much obliged vortec.
bsa

 

They are the same. Some might say that the Z rear is better because there is a chance of it being a posi (don't think RSs came with posi).

I see you are from stateboro, and I think we have chatted before. Myself and another member might be going to Savannah Dragway tomarrow night (I am definatly) for Test'n'Tune. You should join us sometime.

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If you live in Southeastern US, check us out!
South East Thirdgen


ASE Master Tech + L1
Savannah, GA

'87 Trans Am
S/D TPI retrofit including functional PassKey, 22# injectors,
JET AFPR, Ported Plenum,
TB Coolant Bypass,
SSM SFC, Boxed LCAs,
8mm Accel wires,
Flowmaster Exhaust,
16" GTA rims,
Corvette Servo,
KYB Shocks
-->14.97 @ 94.9 MPH<--

'97 Bonneville SSE

 

GM, Hey buddy. I wan wondering when they had test and tune at savannah. I usually go to reynolds and they have theirs on Friday. I'd like to join ya'll this week but of course the rear end fell out of the car.......anyway, you read the post on sethirdgen. When does the season close this year? I might be able to make it another time. BTW, so you're saying not all 91 Zs came with posi.........
bsa

 

I guess you can count me among those that would say that the Iroc or Z28 rear end is stronger than a RS. The 9-bolt is stronger for several reasons: 1) larger ring gear, 2) stronger internal design of case, 3) less likely to lose an axle (4 bolts retaining it vs a C-clip). Now on to the better for posi vs. open diff reason. Also the posi on a 9-bolt can be rebuilt or adjusted for how strong you want it to lock up by shimming the clutch cones. The 10-bolt can be built up to be about as strong, but out of the box a 9-bolt is stronger.

 

I don't think haveing a Z automaticly gave you a 9-bolt.

------------------
If you live in Southeastern US, check us out!
South East Thirdgen


ASE Master Tech + L1
Savannah, GA

'87 Trans Am
S/D TPI retrofit including functional PassKey, 22# injectors,
JET AFPR, Ported Plenum,
TB Coolant Bypass,
SSM SFC, Boxed LCAs,
8mm Accel wires,
Flowmaster Exhaust,
16" GTA rims,
Corvette Servo,
KYB Shocks
-->14.97 @ 94.9 MPH<--

'97 Bonneville SSE

 

9-bolts were only available from 85-89 or 90., Since people talk about the RS they usually mean 89-92, and the Z28 is 91-92, we're comparing 10-bolts to 10-bolts. And they're the exact same. Only the gears and the posi are different.

 

BORG WARNER 9BOLTS ARE CRAP AND DONT HAVE MANY GEAR OPTIONS. AND THEY WERE ONLY OFFERED FROM 85-89 AS AN OPTION. I WOULD PERSONALLY HAVE A 7.5" 10BOLT RATHER THAN A BW 9BOLT. AND IN 1990 GM CHANGED THE REAREND AXLES TO 28 SPLINE INSTEAD OF 26 SPLINE SO THEY ARE STRONGER ANYWAY.. THERE YOU GO.. TO SET EVERYTHING STRAIGHT.

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1990 IROC-Z L98 350 TPI
AFPR 49PSI, GUTTED AIR BOXES, K&N, RAM AIR, PORTED PLENUM, B&M SHIFTER, 3.23 LIMITED SLIP, DUAL CATS, STOCK SUPER TURBO EXHAUST, COOPER COBRA XST's

MUSTANGS...ONLY 4 LUGS....HAHA THAT IS HILARIOUS.