for 3rdgens?

 

Depends on what year and what diff, but its either a 7.5 or 7.625 Chevy 10-bolt, or 7.75 Borg-Warner.

 

Its of an 89 RS, 305 tbi

 

Count the number of bolts on the rear cover. 9 bolts, it'll be 7.75. 10 bolts, your 89 should be 7.625

------------------
Follow my racing progress on Stephen's racing page
and check out the race car

87 IROC-Z Pro ET Bracket Race Car
383 stroker (carbed) with double hump cast iron heads and pump gas
461 Big Block installed and ready for the 2001 racing season

Best results before the 383 blew up
Best ET on a time slip: 11.857 altitude corrected to 11.163
Best MPH on a time slip: 117.87 altitude corrected to 126.10
Altitude corrected rear wheel HP based on power to weight ratio: 476.5
Best 60 foot: 1.662

Racing at 3500 feet elevation but most race days it's over 5000 feet density altitude!
Member of the Calgary Drag Racing Association

87 IROC bracket car, 91 454SS daily driver, 95 Homebuilt Harley

 

Actually if it's a 10 bolt in a a thirdgen
7 5/8" = 7.625"
Sorry, I'm drunk and can't read either. But Mechanical Engineering will do that to you.

[This message has been edited by RednGold86Z (edited February 02, 2001).]

 

They are 7.5" (7.625") 10 bolts and 7.75" 9 bolt Borg Warners.

------------------
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!

 

GM switched from 7.5" 10-bolts to 7.625" 10-bolts sometime in 85 or 86 for regular cars. The 305 TPI 5-speed and 350 TPI automatic cars got 7.75" 9-bolt rear ends from 85-89 or 90.

------------------
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=-