Slow89Iroc-Z

I installed them myself and it took me about 4 hours. I went from 2.77:1 series 2 carrier to a 3.91:1 series 3 carrier. I set the backlash to .008in, set the pinion preload to 14ft/lbs, and I had to use .060in under the pinion to get a good pattern. Seemed to be a lot but I just went for a drive and the gears are silent. Just to let you all know DO NOT buy the install kit from Randy's Ring and Pinion they DO NOT provide the correct carrier shims or a pinion nut. Get the kit from Raytek or from 9bolt.com. Also only torque the cap bolts to 45-50ft/lbs. I tried to torque them to 65ft/lbs as stated in the directions in the install kit and the bolts just snap. Later

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Thrid Place Camaro Modified, Thirdgenfest '06
1989 Iroc-Z L98 with 60K original miles!!!
Mods: OBDII, 383ci ZZ4 short block, Comp Cams custom XFI cam, TrickFlow CNC Ported Heads, Holley Stealth Ram, Custom Cold Air Intake, 3in dual exhaust

NJITIROC

darnit, i bought the Randys install kit. well i guess they gave it to me for free. do you think it was a mistake or do they all have the wrong shims and pinion nut?

Slow89Iroc-Z

Dunno if it was a mistake. But my kit was sealed when I recieved it soo... You can pick up the shims and pinion nut at a driveline shop. Just bring the pinion and the carrier race with you so they can match it up.

Slow89Iroc-Z

This may help if anyone needs a hard to find part:

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6speedIROC

FYI that the diff digram shown is NOT a posi unit and is only the 2-pin version of the '9-bolt'.
The posi units in f-body's were 4-pin LSD units.
They don't have a straight cross-pin, it looks like a cross with a hole in the center for the posi springs (3 total concentic).

87IROCZ350TPI

That's true, however if you ignore the diff, it's still a great reference. Thanks, Slow89Iroc-Z.

Jer82Z28

Can you explain how you guys set the pinion preload before installing the pinion nut? I'm rebuilding my 9bolt atm and I dont understand the whats meant by pinion preload?

Pat Hall

Physically impossible. You accomplish the proper amount of pinion bearing preload by tightening the pinion nut. And since there's not a solid pinion spacer available for the 9 bolt that I'm aware of, you have to use a crush sleeve. It takes an enormous amount of torque to start collapsing the sleeve (usually between 300-400 foot pounds). Once it does start to collapse, you have to go really slow and check the rotating torque with an inch pound torque wrench frequently until you achieve the proper amount (20-30 inch lbs. for new bearings). The only thing you adjust on the pinion prior to setting the preload is setting the proper depth. You use pinion shims to do this, and when you achieve a good looking contact pattern on the gear teeth, you're there. Most times, if you re-use the original pinion shim, it'll get you where you need to be. There's specialty tools available for setting the pinion depth, but due to expense of them and the fact that they're a PITA to use properly, it's a lot easier to set pinion depth by looking at the contact pattern.

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89RS w/350 TPI; 69RS/SS w/450 HP 350/Muncie 4-Speed "Too weird to live, too rare to die."

Jer82Z28

ahh yes now I understand. The way I was reading it in my book was saying to set the preload and then instal the nut. Needless to say i was scratching my head on how to do that.

Thanks for the clarification!