I want to swap my open 3:08 to a posi 3:23 rear end. Will I notice any difference in my acceleration/ performance?
How can I identify a posi rear end if I can't read the code. I was told that if you turn the U joint connection on the front of the axle both wheels will turn forward. Is that true? Please advise, thanks.

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'85 Z28 Copper/ Gold, LG4
dual snorkel w/ ram air, Accel Cap Rotor and 8MM wires, Edelbrock Headers, Catco Cat, Flowmaster 80 series
American Racing Wheels. 350 crate in the future.

 

Yea, a posi the wheels will turn the same way when you turn the pinion. Turn it back and forth a few times, I have seen a few gummed up non-posis turn both ways for a little bit and then turn opposite directions.

A 3.08 to 3.23 isnt much of a change. It will help a little, but not significantly. I'd be surprised if you picked up a .1 in ET from hooking up better.

 

actually I can tell you from the other direction that i definately LOST some performance going to a 3.08 posi.
I am in the process of rebuilding my old 323 and stuck in a used 308 posi for now.
it gets great mileage and you can hit 120 in drive but the ride from 0-60 has lost at least a car length.
I know this because I raced my best friends 87 gt mustang with the 323s and beat him by a car length to 60 from a stop and now I can only tie him until we hit 85 or so when I pull away (ram air I think)
but long story short if you are buying new gears get at least 342s or you will kick yourself.

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88 WS6 T/A 305 TPI--
K&N,Air foil,hypertech chip, thermostat+fanswitch
free mods, dynomax exh, urethane motor+trans mounts,
SSM frame con, Bilsteins
very trick homemade ramair, Accel 300+ ignition system.
http://www.geocities.com/transam617

 

I just swapped from an open 3.08 to a posi 3.73 rear. The car definetaly goes through the gears a lot quicker, but it doesn't launch that much harder even though it is now a posi. I'm now looking to upgrade the suspension so I can plant the rear like my bro's 5.0 Stang does. I can spin all the way through first with my L03 no problem, and it dynoed at 158 hp.

Overall acceleration is better for a given gear, but at a given speed I'm at a higher RPM or maybe even a higher gear.

Overall, the biggest improvement is driveability. The car is much easier to start from a stop, the shifts seem much smoother for some reason, and the car is generally more fun to drive. Unfortuantely I haven't been to the track yet, but on my 3.08 open rear I ran 15.7s.

BTW, WHEN MY CAR WAS ON THE LIFT, THE WHEELS DID NOT SPIN THE SAME WAY. The posi works, but turning the wheels is NOT a way to tell.

Hope this helps,

Jason

[This message has been edited by 89BlwnRs (edited February 04, 2001).]

 

My dad switched from a 10-bolt 3.08 open to a 9-bolt 3.27 posi and he says he loves it.

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West Coast GM Shootout 2001!
1991 Camaro Z28
5.7L 5-Speed (originally 305)
13.25 @ 107.18 MPH
Southern California
Member: SoCal 3rd Gen F-Bodies
Webmaster: SoCal F-Bodies
-=ICON Motorsports=-

 

You should feel a good difference, maybe as much as .3 off your 1/4 ET. You also wont have much trouble hooking up right off the line.

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1987 Chevy Camaro IROC-Z
L98 TPI 350 (5.7L)
TH 700R-4 Transmission
Borg Warner 7.75" 9 Bolt Rear End

Current Mods: LT4 Hot Cam, Comp Cams 1.52:1 Roller Rocker Arms, Edelbrock TES 1 5/8" Headers, Hooker 3" Aerochamber Cat-Back System, Performance Resource Chip, Accel Ignition Coil, Cap, Rotor, 8.8mm Wires, K&N Filters, JET TPI Air Foil, All Free Mods, Falken ZIEX Z-Rated Tires.

Best ET (w/o LT4 cam): 14.32 @ 97.7mph
(corrected for elevation)

7.5" 10 Bolt with 3.42s soon to come!

 

I went from a 3.08 drum set-up to a 3.23 disc limited slip (I did it to get the car back to its orginal rear end). Love it.

JamesC

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Thanks for all the responses guys. I'm doing the swap in few weeks. I'm sure I'll ask some intall hoew to's. I'll let you guys know ! Thanks again.

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'85 Z28 Copper/ Gold, LG4
dual snorkel w/ ram air, Accel Cap Rotor and 8MM wires, Edelbrock Headers, Catco Cat, Flowmaster 80 series
American Racing Wheels. 350 crate in the future.

 

89BlwnRs, what kind of car did the 3.73 come out of, and was it disc?


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Rob
'86 TA 305 TPI
Gutted MAF
Ported Plenum
TB Bypass