Bigger pictures: Eaton Posi Install Instructions
Eaton Installation
OK, I decided to take on the Eaton install recently and, while the Eaton instruction were great, I felt there were a couple things I could have benefited from knowing about. This is by far the biggest project I have attempted. I mostly tinker, but if I can do it then you should be able to do it. If you have any questions, feel free to ask.
Let me preface this by saying that the instructions that I put down on here are mainly copied from the instructions that Eaton send to me. I added pictures and a little more information that I thought would be helpful. Click on any pictures to see the larger version.
Instructions From Eaton
Hardware/Tools Needed
1. Vehicle service manual
2. Vehicle hoist or hydraulic jack and jack-stands
3. Air Impact gun and sockets or equivalent hand tools
4. General socket and wrench sets standard and metric
5. Shop light
6. Oil drain pan
7. Shop towels
8. Gasket scraper and/or drill attachment to remove gasket
9. Magnetic base dial indicator
10. Mechanics magnet (I didn't use this)
11. Large pry-bar (good to pry out the differential - a must have)
12. Drift punch and hammer
13. Hydraulic press (for pressing bearings on carrier)
14. Bearing driver (I didn't use, but I had a shop put the bearings on)
15. Heavy leather or Shot filled rubber hammer
16. Shim driver (I didn't use, but may have made it easier)
17. Torque wrench (a must have - I needed one up to 150ft-lbs for the brake components)
18. Flexible funnel
Step 1
The rear axle wheels must be raised from the ground and the vehicle secured in a safe manner. Remove your rear wheels. The use of a vehicle hoist is preferable, however the installation can be accomplished at floor level. I did it with jack stands and had plenty of room.
Step 2
Remove rear discs. After you have taken your wheels off you have to remove your rear discs. To do this you have to take off the calipers and caliper mounting hardware. It's much easier to take off the calipers and then the mounting brackets. I didn't take off the calipers because I didn't need to to get the assembly off, but to get them back on you really do need to take the calipers off. otherwise your calipers will not be spread out enough to be put back on the disc. I breaker bar works best to take off the caliper mounting bracket bolts (shown here with penetrating oil on them). They are put back on at 148 ft-lbs so a breaker bar is really necessary to get them loose.
Once you get the assembly off set it on the leaf spring or hang it by a coat hanger, taking care not to crimp any of the lines. The next thing to do it to take off the discs. Make sure your front wheels are blocked and undo your parking brake (if you had it set). If you try to take the discs off with the parking brake on, you'll be there for a while.
Step 3
With the use of a drain pan, remove differential cover. Helpful hint: Leave the top cover bolt loosely engage while prying loose the cover. Fully remove once gear oil has been fully drained. Take note of the type of cover gasket used, as replacement with a similar gasket material is recommended. Scrape and clean cover. I used a plaster knife (barely visible in the 3rd picture below) to scrape off the old gasket material and got a little abrasive wheel from 3M that I put on the drill to help get off the harder stuff. That along with some sandpaper did the job. Make sure you cover up in internals so as to not get all that crap in there as you are scraping it, you wouldn't want your ring and pinion gears seeing that later. Note: Dispose of waste oil properly.
Step 7
Remove both left and right differential side bearing caps. Be sure to mark or tag them (left/top and right/top) as they will need be reinstalled in their original position and location.
Step 8
Eaton says to temporarily re-install the differential pinion shaft as shown to assist as a leverage point in removing the differential, but I didn't do that,. Once the pinion shaft is in place as shown, carefully pry the differential assembly outward. Support the assembly with your hand to keep it from falling out. Note: Do not pry on the ring gear teeth as damage and noise could result. I wrapped some wire around the diff shaft and pulled while I had a towel sitting on the bottom of the housing to cushion a fall if the diff popped out and dropped on the housing. You don't want to damage that ring gear. An easier way (and more controlled way) is shown below by prying on the ring gear bolts. I was much more comfortable doing it that way(more control). I was hesitant on prying on bolt heads, but was told to do so by a couple of shops that said that is how they got the diffs out.
Once the differential is free, remove it along with the left and right differential side bearing cups/races and shims, keeping track of their left and right orientation (although you will probably need an adjustable shim pack to get the Eaton back in with the proper backlash)
This is your view with everything out.
Step 9
Remove ring gear bolts. Note: The ring gear bolts for my 01 Silverado have left handed threads and need to be removed accordingly in the reverse direction (the heads are marked with an "L"). In order to remove the ring gear bolts you either have to have an impact gun capable if taking off the bolts or you have to have a big vice to clamp the diff in and loosen the bolts. I had an impact gun/compressor combination that judt wouldn't take the bolts off. I'm not sure which was the problem, but it didn't happen and I ended up going to the sears auto shop and have them loosen the bolts.
In my case once the ring gear bolts have been removed, the ring gear is still pressed on the differential housing pilot diameter. You can either press it off, or do what I did and use hammer and drift punch. The punch can be used through the ring gear bolt holes or along the outer edge of the ring gear. Note: some differentials have a speed pick-up ring located between the ring gear and the differential housing flange(mine didn't). Take note of its orientation during removal so that it can be re-installed properly. Note: Do not strike the speed pick-up ring as it can be easily damaged or broken.
Step 10
Install new differential side bearings on to the bearing hubs of the differential housing. I had this done at a shop, but I think that I could have put the new bearings in the oven (cranked up) for 20 minutes and slid them on the Eaton (that's what they did). Prior to pressing the new bearings on to the differential bearing hubs, be sure to wipe clean both surfaces. Note: Please make sure that the new bearings are fully “seated” against the housing bearing hub shoulder.
Step 11
Prior to installing the ring gear on to the differential housing flange, be sure to wipe clean the ring gear mounting surface and the housing flange mounting surface. This is to insure that no debris is trapped between the ring gear and flange adversely effecting ring gear backlash. Once clean, align the through holes of the flange with the threaded holes of the ring gear and “start” all of the ring gear bolts in their threads. The ring gear can either be “drawn” on to the press fit of the housing ring gear pilot diameter by equally and alternately tightening the ring gear bolts(this is what I did), or the ring gear can be fully “pressed on” using a hydraulic press and then fully tightening the ring gear bolts to the proper torque specification afterward. This is where you need a vice if you are going to draw on the ring gear. I didn't have one and there was no way that I was getting the ring gear to the torque spec called out(75ft-lbs). I had to find a shop that had a vice big enough to clamp down on the diff to hold it in place while I torqued down the ring gear bolts (in a star pattern). Note: some differentials have a speed pick-up ring located between the ring gear and the differential housing flange. Re-install it in the same orientation as it was removed. Note: The picture shown below does NOT show the vice that one would need.
Step 12
Firmly grasp the entire differential assembly that now includes the differential side bearings and ring gear. Add to this the side bearing cups/races and the side bearing shims (keeping left and right side shims in their proper place). All of these components must be hand pressed in place (as far as possible) in the axle housing, taking care to align side bearing cups/races and shims properly. The differential assembly can then be firmly seated with the use of a leather or rubber tipped heavy mallet. Once the differential assembly is fully seated, make sure the side bearing shims are fully seated as well, by using a special shim driving tool or a suitable drift punch and hammer.
Here is where it got tricky in my case. I didn't have a shim driver (don't even know what it looks like), so had some issues. What I did was put the left bearing race and shims in and set the eaton in. I have the right side bearing race on and then went to put in the right side shim. In order to do this you have to "rotate" the bearing race open enough so you can start the shim in. Well when you do this the shim and bearing race are now not exactly perpendicular to the axle shaft, so you will, in essence, be driving the shim into the side of the carrier (third picture). What I was told to do, and ended up doing, was to place a punch (shown as a solid red line below) between the race and eaton and push the back (with respect to the front of the truck) of the race outward using the punch as a lever and tapping it with a rubber mallet(yellow arrow). This helped to true up the race and shim face parallel to the axle housing face (perpendicular to the axle shaft). You can then knock the shim set in with a rubber mallet or soft-blunt copper punch.
Keywords: Eaton Posi Auburn Differential Diff Carrier Installation Install Instructions
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Originally Posted by 05chevyguy
