I have a 1989 Formula 350 with dual cats,WS6 option, and what I think is a 327 gear borg warner 9 bolt rear end. I am having a hard time finding info on this, such as ring gear size,pinion splines, axle splines, and is this a 10 bolt rear with a 9 bolt cover? I would be gratefull for any info.

 

aahhhh, you have one of those jewels. actually, my opinion is it's a better rear end than the other choice they offered in those few years. it's an austrailian made borg warner axle with little to no info cerculating through the aftermarket. it was offered in only three gear ratios. 2.77, 3.27, 3.45. the axle code for your 89 3.27 is GW6 which should be on your options sticker in your center consule box (stuck under box door or on inside-side). 2.77/3.45 codes are GH3/GM3. try your local gm parts house but good luck. when your asking around, don't be surprised if you get some funny looks when you say gm 9-bolt, most people never heard of them except 3rd gen nuts.

 

the ring gear size is 7.75.

 

I have parts available (ie for sale) for 9 bolts including brand new OEM tooled series 3 posi carriers, ring and pinion ratios of 3.2x, 3.45, 3.73 and 4.10. Note that the 3.73 is a true 3.73, not the 3.70 that everyone else advertises (even though they advertise it as a 3.73). The difference? The 3.73 has the stronger 11 tooth pinion vs the weaker 10 tooth pinion on the 3.70. I will also have other stuff available soon.

And yes, the 9 bolt is superior to the 10 bolt. That's why it was the high performance option.

Miles

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88 427 Big Block Camaro
(Best 1/4) 12.18 @ 113mph 1.75 60ft
(Best 1/8) 7.76 @ 94mph 1.72 60ft

Currently installing 3.73's into my 9 bolt (YES, it is a 9 bolt & YES they are 3.73's, not 3.70. I currently have 4.10 gear sets and new series 3 posi carriers for sale for 9 bolts )
www.koolmeister.com