This post is a work-in-progress -- I'll be editing and updating it as I write more, but I wanted to get it started or I'll NEVER get it done!!! Feel free to comment and share experience, knowledge and questions in posts even though it's not done.
I will begin to explain some of what's involved with doing a full carrier replacement, and some of what you are looking at doing it with a Ford 8.8 axle. I've only done it with the Auburn ECTED, but I bet most of it is relevant no matter what you do.
There are two broad cases you will encounter: Keeping your ring and pinion
-- or -- Using a new ring and pinion
The case of keeping your old ring and pinion is the easiest. One assumes that your existing ring and pinion are already set up properly.
Most of you will be doing this to your existing axle, and keeping everything but your old carrier. This means the only bearings you need to replace are the carrier bearings. If you decide to replace your axle bearings and seals, keep in mind which axle you have when buying the bearing set. 28 spline axles have 2.25" diameter axle bearings and seals, and 31 spline axles have 2.5" diameter bearings and seals. You can pound out the old bearings with a long pipe with the differential carrier and axle shafts removed. When you reinstall the new ones, use a method like in note number 9 below.
Basically, what you will be doing is taking out the carrier and removing the ring gear and "tone ring", then putting that and new bearings on the new carrier and reassembling the carrier into the axle. You will NOT be doing ANYTHING to the pinion and trust me that's a blessing!
Some things to remember if you are keeping your existing gears or not -- that is, things that always apply
1. Bearing caps and the recess for the bearing race on the differential housing are individually machined. Make sure you mark the bearing caps "R" and "L" and don't mix them up. Mine came unmarked with the used axle already disassembled, but there were marks on the inside that made it possible to figure out which was which, fortunately.
2. You will need the tone ring from your old differential, or a new one. I had a bad LS carrier that was given me with the axle (it wasn't the one that came in the axle) so I had one to remove a ring from. I'll cover taking off the ring gear later.
3. With some differentials, the center pin will not come out enough to install the c-clips if you have high ratio (4.56 and up, but maybe 4.10 on some differentials). You will have to grind a flat on the pin so it can be turned 90 degrees and slid out enough. The differential installation instructions cover this, but not real well in the case of the Auburn ECTED since the instructions reference a pin from their cone type LS which is slightly different. The difference is where the retaining bolt goes in -- but if you're new to it, it can make you doubt what you're about to do as you are about to modify a key component of the diff. I didn't want to modify mine, and tried to assemble it without doing so (I changed to 4.56 gears) -- but that turned out to be a time waster. Almost none of you have anything but 4.10 or lower in your truck already so this probably doesn't affect you.
4. You absolutely must shim the differential carrier per the instructions, and you must use either the feeler gauge (iffy) or micrometer (preferred) method to determine gear lash. FAILURE TO SET PROPER LASH CAN CAUSE CATASTROPHIC FAILURE OF THE DIFFERENTIAL.
5. Observe all torque specs. Beg, borrow, or liberate
torque wrenche(s) of the proper ranges.
6. Read all you can about the procedure (NOT JUST THIS POST) before you try anything.
7. You must either heat up the ring gear and the carrier bearings to install them, or press them on. I used heat, but either works. You will find references to it in full install instructions. Do not exceed 300 degrees. You do NOT heat the carrier itself!
Some additional notes for those doing gear swaps
8. Like the carrier bearings, the inboard pinion bearing must be pressed on the pinion shaft, or the bearing heated so it will go on. In either case observe the warning about not overheating the bearings.
9. The ouboard pinion bearing is pressed into the differential housing. A large socket or pipe that fits in the hole in the housing can be used to hammer it home (hitting the pipe or socket with a hammer, not hitting the bearing). MAKE SURE THAT THE PIPE OR SOCKET ONLY CONTACTS THE OUTER RACE OR YOU WILL DAMAGE THE BEARING! Use as much force as necessary on the hammer, but you don't have to be a total animal to get it in place. When you remove the old bearing by hammering from the inside, it doesn't matter if you damage the old bearing. Make sure the new bearing seats all the way down.
10. The pinion uses a crush sleeve under the flange to ensure you can have lots of torque on the mounting nut, without overloading the tapered bearings. This leads to confusion. You will be told the nut gets tightened with 300 pound feet of torque to crush the sleeve, but then you are warned not to exceed a bearing preload torque of 19 to 29 pound INCHES! This is not an error. The tightening torque is with the pinion IMMOBILIZED to tighten the nut. The preload torque is how much force is required to turn the pinon freely after the nut is tightened down. Failure to tighten the pinion nut enough will result in play in the pinion and eventual failure. Too much torque will result in excessive bearing wear.
11. Shims need to be CLEAN when installed. Excess oil and dirt on them artificially inflates their thickness when stacked (and you will be stacking them) but then that will go away after a time in use and everything will "open up" -- you don't want that. Wipe them every time you handle them if you can.
12. As I mentioned previously, particularly in the case of the Auburn LS and ECTED, you must do something if you have gears over a 4.10 ratio. For those gears, you have to take the center pin out of the diff and machine/grind it down with a flat on just over half it's length, about 1/10" deep. OTHERWISE, you can't get it out enough to push the axles in far enough to get the c-clips on -- ask me how I know... I ended up having to take the carrier out, remove the ring gear from it, remove the pin, grind it down, and put everything back together before I could get the axles in!
13. You may have a problem with the ECTED if you have a 31 spline rear. The splines on some axles (the right one in particular) aren't cut along a long enough portion of the axle. The ECTED has one very long splined spider gear for the right (passenger's side) axle. The result of this is that the 31 spline shafts on my FX4 axle wouldn't go all the way in far enough to put the c-clip in. I actually had to grind away on the shaft a bit just behind the splines, to the depth of the splines, to allow the axle to go in far enough.
I'll be posting on this further, but thought I'd share these hard earned words of wisdom.
My buddy Billy at work helped me with the setup. He thought it would be a 1 hour job but he didn't catch that I wasn't using the original pinion and ring. Hence -- it's a lot more work.
You have to press the bearings on the differential and the carrier. Not a home job unless you have some kind of press. You can also heat them up and drop them in place, which is what our machine shop did after the inspected the bearings and decided they didn't have any plastic in them.
To put the ring gear on, you heat it in the oven. I did mine at home by putting it in the oven set for 250 for about 1/2 hour. It just dropped in place then. Line up the bolts, put a couple of them in, and you're there.
Here's some of the VERY few pictures I took during this. It's too dirty and nasty for much of it to use the camera -- especially working much of it alone.
Billy gets some shims together for the adjustments.
Looking into the rear, you can see the black magnetic coil on the right that engages the locker (note the wires hanging). Runs on it's own bearing. The rear is shimmed here to about the right lash, and we're about to check the mesh. The pinion is in with shims, and the bearing pressed in the housing and on the pinion, but without the crush sleeve for a trial fitting.
Billy is painting on the marking compound that will allow us to see if the gears "mesh" correctly. If they don't, we'll have to try different pinion shims. I "guessed" that we should use 0.036 shim (thicker than normal) because of the high ratio. I turned out to be right on, but not by skill. My best guess based on what I read was correct. Billy had no idea where we should start so I just read everything I could get my hands on about Ford rears and it was suggested by some installers that 8.8's with high gear ratio's need somewhat thicker shims between the pinion and the bearing. If you guess wrong, you have to press the bearing off, put new shims on, and press the bearing back on again
This is a near perfect mesh pattern! Hooray! This was on Friday about 2PM -- getting late since I want to use the axle the next day. The master rebuild kit I used had instructions to show you what were acceptable mesh patterns.
Putting the pinion back together with the air gun. It wasn't enough to crush the sleeve. When we put real torque on it, the screwdriver you see holding the flange snapped like a twig and we had to use bolts instead. THEN we could hardly keep the axle DOWN while we torqued. Sometimes you just can't win.
Then of course, the air gun falls apart and little pieces go missing. What a day...
Let's just say doing it from scratch with a new carrier, ring and pinion is a lot of work, and sometimes you end up backtracking.