I'm confused between the two words "Differential" and "Posi Unit". I currently have 2.73s and want to upgrade to 3.73s. I want to have a 3-series carrier for the 3.73s...so does this mean I have to get a 3-series "posi unit" or will I need to get a new "differential"....or both? I'm confused. I need some serious education here. Can someone clear this up for me?

The reason I ask is because I want to make sure my stock 7.625 rear-end will be strong enough to handle the 450hp 350 engine I put in during the summer.

Thanks.

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1992 Z28 (305) TPI.
160' stat, Accel 8mm, Accel Cap & Rotor,
Flowmaster, high-flo cat.

 

Well, how's this: A differential (or carrier) can be either a posi unit or an open unit (or a locker, or a spool, or ...) The differential is the thing the ring gear goes on.


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-Tom P (Hot rodded 1986 Firebird 2.8l) from http://www.f-body.net/mailbag/3rd/3rd_mailbag.html message boards
---Think your car could be pic of the week? Visit http://www.f-body.net for details!

 

That makes a lil more sense. So does this mean I am moving in the correction direction to a stronger rear-end? I still need more advice. Thanks again.

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1992 Z28 (305) TPI.
160' stat, Accel 8mm, Accel Cap & Rotor,
Flowmaster, high-flo cat.

 

The differential is usually the guts behind the diff cover(the part that differentiates the torque) The carrier "carries" the ring gear. 3 series carrer(posi or open) aren't stonger than a 2 series carrier. The 3 series what you got if you had 3.23 or deeper gears. You can get 3.73 2 series gears. Put in a powertrax, new bearings, support cover, synthetic lube, weld the axle tubes, don't run slicks, don't abuse it, and will last a while. That rearend wasn't built to withstand alot of power and abuse, so don't be suprised if it doesn't last a long time at the 450 hp level. If you spent the money on a good engine, why not install a killer rear-end(9 inch ford)?


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82 camaro--original steering wheel, brake/gas pedals, seats--everything else modified
82camaro

 

No, a spool is *NOT* a differential. A differential allows one wheel to turn at a different speed from the other so they can both be driving when going round a turn without one wheel spinning or the car trying to go straight. However, if one wheel loses traction, it will just spin and the other one won't drive at all. "Positraction" is the GM brand name for a limited slip differential, which has clutches to keep the other wheel driving if the first wheel loses traction. It is a compromise solution, since the clutches will only transmit so much torque, but still enough to cause the inside wheel to spin a little on sharp turns under power. A Torsen differential is a special kind of limited slip without clutches that gives more torque to the wheel with better traction to keep the other one from spinning. A spool replaces the spider gears in a differential to lock both axles together at all times. Great on the drag strip, but on the street it will understeer severely, trying to go straight, until you apply enough enough power to break both rear wheels loose. This kind of agressive driving is frowned upon on the street, which is why spools are recommended for off-road only.

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1985 Yellow IROC-Z 5.0 HO, T-5 3.73 Posi, 4 wheel disks
PFCM pads, GTA wheels, Koni yellows, B&M Ripper, Dynomax

 

I don't wanna buy a ford 9 inch...so what can I do to my rear-end now so it'll hold? I still want to install 3.73s.

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1992 Z28 (305) TPI.
160' stat, Accel 8mm, Accel Cap & Rotor,
Flowmaster, high-flo cat.

 

Oh...and thanks for clearing up my confusion

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1992 Z28 (305) TPI.
160' stat, Accel 8mm, Accel Cap & Rotor,
Flowmaster, high-flo cat.

 

Viewed in that way, yeah. I was just trying to show what part of the axle a differential was, not suggesting a spool or a locker. Thanks for clearing that up!