I have the stock 2.72 rear out of an 89' IROC 5.7L I want to change to a 3.73 ratio. Do I have a 26 or 28 spline pinion? Where is the cheapest/best place to get these gears and some form of locker or posi unit?

 

Ok, since you have an 89 5.7L with a single cat, you have a 9-bolt 2.77 rear end. You're screwed as far as changing the gears, because NOBODY makes gears for it. You have to swap your whole rear end for something else. You need to find an 89 9-bolt with a 3.27 or 3.45 rear end, or a 90-92 10-bolt with a 3.23 or 3.42 rear end, or you can use a 93+ 4th gen rear end.

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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=-

 

Blue Iroc your best bet is to look for one at a salvage yard. I did and found one fairly cheap.

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Big 454 '86 Camaro Z28 '72 Nova w/454 BBC

[This message has been edited by Big454blockchevy (edited January 06, 2001).]

 

Gears are available for the 9 bolt.
They are expensive though, I have seen 3.70 ratio for $300. I'll post if I run accross the site/message again or just do a search in the archives for "9 bolt".

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86 Camaro Sport
383 Speed-O-Motive Crate Engine, Trick Flow Twisted Wedge G2's, 58mm Accel TB, 3.73 Auburn Pro, SLP Cold Air Induction and Headers, Dynomax Cat-back, Serpentine Belt Setup, Dual IROC Fans, Jamex springs, 16" IROC Rims, 36mm/24mm Sway Bars, Global West Steering Brace. Hotchkis Rear LCA's,Panhard Bar and SFC's.
http://www.sethirdgen.org/octride.htm