12-Bolt Spool Bearing Pre-Load

[Cdncarnut]

I have searched this entire forum and cannot find the answer.

I am doing a ring and pinion swap in a 12-bolt, in my Stocker, and would like to know what everyone is using for the pre-load for the spool bearings.

I realize that the spool should spin as freely as possible, but how many thousands is the minimum pre-load that is acceptable.

Thank you in advance.

[Dragsinger]

Thomas,

my method that has proven to give excellent results;

I select a shim pack that provides the backlash number I want and those shims will GENTLY tap into place with a small hammer. Thus, very light preload. It does require several trial fits to sneak up on the combination.

And speaking of preload, I also use very light preload with the pinion bearings and install a solid spacer that adjust with a shim pack.

When the install is complete as I describe the complete assembly is very easy to turn and the car is very easy to push.

[Danny Ashley]

Thomas:
I read years ago that the total shim thickness is around .484. I have measured many stock cast iron shims and found this to be pretty accurate. My latest one came in at .488. I'm sure every housing is different but the .484 will get you in the ballpark. I've done so many that you get a feel how hard the last shim drives in and how easy the carrier comes out. Speaking of which, placing a boxed end wrench on a ring gear bolt so it jams against the housing and rotating the pinion clockwise is the easy way to get the carrier moving out enough to get 2 pry bars in the bearings/shims. Hope this helps.

[Ed Wright]

Proper pre load will cause every roller to roll anytime you rotate the spool.

[Dragsinger]

What Ed says is correct, that is my method. All bearings in the assembly have "just enough" preload to made that happen.

In my experience, there is no need for preload beyond just having the slack out.

NOTE: with a situation of very high horsepower the setup could be different but I do not deal in that area. My experience is with stockers, super stockers and street driven cars.

I like the Chevy 12 bolt and think it is a good choice for many builds. Yet, the factory housings are disappearing quickly.

[Ed Wright]

Moser has a very nice 12 bolt. That is what I use, their whole 12 bolt rear end. Order the width you need, bolt circle, etc. Good people to deal with.

[Lew Silverman]

I've had good luck with the "Super Shim Pack" kit from Randy's Worldwide (www.ringpinion.com). The shims fit between two halves of a machined spacer, which makes installing them MUCH easier. They also have have the crush-sleeve replacement spacer and shim kit that Larry mentioned as well.

Lew