I have found out that I have a GM 10 bolt rearend with a 3.08 gear and 26 spline axles and now i just need to know what the ring gear diameter i know that it is either 7.5 or 7.65. I would take it apart to find out but it is a daily driver and dont have the time. Any info would be great...it there is any indicators just let me know. The car is an 88 IROC with a five speed. just let me know

 

i thought all irocs were 9 bolts? why do you need to know the ring gear size? for a replacement gear set? they're the same part for 7.5 or 7.62 ring gears as long as it's a 10 bolt and you buy the correct gear for a 10 bolt you'll be fine. if you look at a catalog you'll notice it says for a x:xx numerical ration and higher and another gear set for x:xx numerical ration and lower. the ratio is about all you need to know.

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ICON Motorsports
1st & 3rd
MM Black Diamond 538 F&AM

 

The 7 1/2" ring and pinion are interchangable with 7 5/8" gears. They'll both use the same carrier.

If it's really a 9 bolt then you need 7 3/4" gears and won't find them in any real catalog listings.

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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 (times are for the current engine)

Best ET on a time slip: 11.447 altitude corrected to 10.99
Best MPH on a time slip: 119.42 altitude corrected to 124.86
Altitude corrected rear wheel HP: 493
Best 60 foot: 1.586

Racing at 3500 feet elevation with a typical race day over 5000 feet density altitude!
Member of the Calgary Drag Racing Association

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

 

But I've got new 4.10 ratios and series 3 carriers available. Other ratios (3.4x and 3.73) will be available soon.

Miles

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88 427 Camaro
12.18 @ 113mph 1.75 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 carriers in stock for 9 bolts )
www.koolmeister.com

 

Yes, some IROCs did come with the 7.625" 10 bolt, but most had the 7.75" borg warner rears. But I think 7.5 and 7.625 parts can be used interchangeably.

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1987 Chevy Camaro IROC-Z
L98 TPI 350 (5.7L)
TH 700R-4 Transmission
Borg Warner 7.75" 9 Bolt Rear End with 2.77:1 Gears.

Current Mods: LT4 HOT Cam, Comp Cams 1.52:1 Roller Rocker Arms, Accel High Flow TPI Baseplate, Edelbrock TES 1 5/8" Headers, Catco 3" High-Flow Catalytic Converter, Hooker 3" Aerochamber Cat-Back System, Transgo Shift Kit, Performance Resource Chip, Accel Ignition, K&N Filters, Jet TPI Air Foil, All Free Mods, Falken ZIEX Z-Rated Tires.

Best ET: 14.32 @ 97.7mph
(corrected for elevation)

 

Only the 87-89 IROC's with 305 TPI 5-speed with G92, and the 350 L98's are 9-bolts. 305 TPI automatics from 85-92 are all 10-bolts.

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1991 Camaro Z28
5.7L 5-Speed (originally 305)
317 RWHP, 418 RWTQ
13.23 @ 107.62 MPH
Southern California
Member: SoCal 3rd Gen F-Bodies
Member: SoCal F-Bodies
-=ICON Motorsports=-

 

Hey Kevin91z, would my 89rs be a 9 or 10 bolt? does that have any relation to the number of screws holding the cover on the diff? Thanks


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89 RS Camaro, LO3 305 TBI
Autometer Air/Fuel Ratio Guage
Cooling Fan Overide Switch
L69 Duel Snorkel Intake
Dynomax Ultra Flo SS Cat Back

 

"305 TPI automatics from 85-92 are all 10-bolts."

Try and tell that to my 2.77 BW 9 bolt.

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86 T/A 5.0 A4 & 2.77 gear
15.62 @ 86 mph
93 Civic 1.6L
13.5 @ 100 mph

 

i have the 10 bolt in my 89 iroc.

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Brandon
"ScreaminDeamin 360"
350 60 over, TRW forged 9.83:1 pistons,Hooker Comp headers, crane cam 216/228 .484/.512, crane 1.6 RR's, ported plenum, home made ram air, 24lb SVO injectors, crane AFPR, all going through 3 inch mandrel pipe and a flowmaster.
New project-89 IROC-305 5spd...Jamex Springs...and thats just about it!Soon- 6 speed, Pro 5.0 shifter and 4.10's
http://users.argolink.net/bvana

http://ScreaminDeamin.cz28.com

 

T/A's went to 9-bolt in 86
Camaros went in 87

All models lower then IROC/Z28 or not having G92 5L or 350 will have a 10-bolt

7.5" was 82-86 (I think)
7.65" was 87-92 and on I believe

you probably have a 10-bolt 7.65"

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1989 Trans Am GTA, L98 5.7L TPI, TH700-R4, T-Tops, dual cats, 9-bolt rear, 3.27, Dynomax muffler, K&N
1992 Camaro RS, LO3 5.0L TBI, T-5, T-Tops, 3.08, L69 Dual Snorkel, K&N - Sold

Honda engines ROCK, I have one on my lawn mower but I still have to push it.

 

Than why do I have a factory installed 3.08 BW 9 bolt in my 86(late 85 produced)IROC