.

 

Very few did, but it's possible.

 

Absolutely possible. The owner of the differential shop where I get all my work done has told me that 1988 and 1989 are transition years. In 1988, the majority were 26-spline axles. In 1989, the majority was the 28-spline.

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Willie

Supercharged 1987 305 IROC-Z, Daily-Driver, Emissions-Legal.
Former Paxton (6-psig): 12.57 @ 111 mph.
Former Paxton (6-psig) & former 50-hp nitrous: 12.04 @ 114 mph.
ATI D1SC (5-psig):
12.26 @ 113.55 mph
ATI D1SC (10-psig): Projecting high 11's.
Future ATI D1SC (15-psig): Gotta catch them pesky 26-psig boosted TTA's!!

http://willie.camaro-firebird.org/

1987 "20th Anniversary Commemorative Edition" Z28 Convertible -- Super Chevy Show Class Winner, 1998.

 

I would bet money that the majority of 89 has the 26 spline axles, mine did, and there are quite a few others here. Lets just say that I have yet to see/hear of an 89 that had the 28 splines.

Mentioned somewhere is the fact that if you has the numerically lower 2.73 3.08 gears that they did in facy have the 26 spline axles. The 28 splines were saved for the higher gear sets.

 

Officially 28 splines came out in 90. The only to know if 88 or 89's have 26 or 28 is to pull the axles and count.

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

87 IROC-Z SuperPro ET Bracket Race Car
461 naturally aspirated Big Block

Best ET on a time slip: 11.242 altitude corrected to 10.89
Best MPH on a time slip: 121.52 altitude corrected to 125.89
Altitude corrected rear wheel HP: 497.9
Best 60 foot: 1.546

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

 

I have yet to see an 89 with 28 splines even though I know some exist. I pulled a rear out of a car manufactured in 6/89 and it STILL had 26 spline axles. Finding an 88 with 28 splines seems impossible (unless 9 bolt). I don't know if they exist or not in 88, but if you dropped an 88 rear in front of me, I would drop $10,000 on a 2:1 bet it has 26 spline axles, and i'm not the gamblin' type.

 

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