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Old 10-13-2003, 10:25 PM
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Eaton posi swap

I'm in the middle of swapping in a posi into my 12-bolt. What's the best way to pull the old diff out? From what I understand it needs to be pryed out. Does anyone have any suggestions as it seem pretty tight. Thanks all.

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Old 10-14-2003, 01:01 AM
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If the axles are out & the bearing caps are off, it should pry out easily with a big screwdriver or a hammer handle. Be sure you have a good grip on it (it's heavy, greasy, & sharp), or it will try to smash your toes.
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Old 10-14-2003, 05:57 AM
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For sure it comes out easier than it goes back in. When reinstallling be very careful to keep the shims in their original positions and go slowly so you don't wedge the carrier and shims in crooked. Tap the shims on each side back and forth with a hammer handle and slowly work the carrier in. Do not hit them with anything metal, as they will tend to shatter.

Vince
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Old 10-14-2003, 07:59 AM
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The axles are out and the caps have been marked and removed. I pryed on it with a large screwdriver and tugged about as hard as I dare and it didn't budge. I bought the rearend a couple years ago and I'm just replacing the factory limited slip diff with an Eaton. It has Timken bearings in it, did GM put Timken bearings in. I'm just thinking that the guy I bought the rearend from may have put these bearings in and that's why it's tight. Also, from your guys experience when using the same gears on a new diff will the existing shims work and if not where is a good place to get some quick as I want to go to the track soon. Also, I'm going to measure the backlash with the new diff and compare to the before #. Thanks for the help!
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Old 10-14-2003, 12:41 PM
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You may have to use something larger than a big screw driver. I used to use a piece of 3/4" pipe about three feet long, sometimes they can be stuck in there pretty good. The proper way to do it is with a spreader that actually spreads the hosing slightly and allows the carrier to drop out.

Yes GM uses Timken bearings and SKF as well. You will just have to install the new carrier and see how it fits. If the backlash feels about right, then get some titanium dioxide and run a pattern check on it. If the pattern is way off you will have to mic the shims and take away from one side and add to the other with new shims. New shims can be had at your GM dealer.

Vince
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Old 10-14-2003, 11:19 PM
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The 12 bolt carrier is installed with a .004 inerferance. In other words, the housing is compressing the bearings and it may need to be spread. There are 2 holes on each side of the bearing journals for this and a special tool that fits into the holes. But you should be able to remove the carrier without it. It may be stuck with varnish or something. Just be careful because when it comes out, it comes out!!!

Now, putting the new carrier in: You will need shims and a dial indicator and a magnetic base. You want to end up with about .006 - .008 backlash on the ring gear when the carrier is installed. Better yet, measure the backlash of your original carrier and set the new one up to duplicate it. Your original shims will most likely NOT work. Get a shim kit from Richmond or the like. Set the carrier in and measure the backlash with the dial indicator set up on the teeth of the ring gear so that the rotation of the ring gear pushes up on the dail indicator. To much backlash: add more shims to the right bearing and subtract the same amount from the right. Too little backlash: add more shims to the right and subtract from the left. Once you have the correct backlash, add .002 to each side for the interferance fit. Now, you can use the multiple shims from the shim kit, or measure the total thickness of the shims (per side) and have some solid ones made and a machine shop. You might even get lucky and have your original shims ones milled.

Whatever you do, don't just stick the new chunk in and depend on luck. Most of the time, you will loose. If you are not sure, take it to someone that knows how to set up rear end. There is nothing worse that tearing up a good set of gears.
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Old 10-15-2003, 07:43 AM
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Thanks everyone. I tried prying it with no luck. It seemed like it was going to take more force to come out than I was going to be able to leverage. I called a friend of mine that has a shop and he gave me a method to try. Put a large screwdriver thru the cross shaft hole, rotate the screwdriver so it rests on the top of the rearend housing. Remove the driveshaft if not already then tap the pinion yoke so the pinion will want to ride up the ring gear (CCW as viewed from the rear of the car). Due to the cut of the gears this will push the diff out the back of the housing. I had the diff out within minutes with little effort. Have you guys ever tried this? Thanks.
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Old 10-15-2003, 07:20 PM
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That is a new method on me, but sounds like a great one.

Vince
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