Okay guys. As promised. I'll keep editing until I get it where I'm happy with it. Still editing as I think of things. Bear with me.
Standard disclaimers. I'm not responsible for your stuff and don't hurt yourself.
Vehicle: 2001 Ford F150 SCab with 8.8 rear diff. This diff is common to a lot of vehicles over a couple decades.
Motivation:
My rear diff was making a little noise and on inspection, I realized that the noise was coming from the right rear. It actually was a brake noise resulting from the axle end play binding the brakes. After a little research I determined in all likelihood the culprit was worn clutch packs in the limited slip unit.
What you need other than the parts:
Dial gauge, micrometer or caliper, basic hand tools, 0.5" bolt 2.5" long with a pair of 1.5" diameter and low profile (thin) nuts.
With the truck up on stands, take the wheels and brake rotors or drums off. I put the dial gauge on the axles (both sides) and measured the end play.
Axle measure pic
Right side was 0.101" and the left was 0.025". I haven't found a spec from a reliable source for this number but I have seen 0.030" tossed out as a max number. This is pretty reasonable considering what I found inside. More on that later.
So I ordered a rebuild kit from Amazon (~$83). I should mention at this point, if you've never done the rear brakes (mine is 2001 with 125k miles and it was all original) this is a great time to do pads rotors and e brake shoes. All of that came from Advance ($150 with 15% off). That also included 3 quarts of Royal Purple 75W 140 ($20 per quart less the 15%). I also picked up new axle seals because it seemed silly to not change them while it was apart. About $28 for them less the core charge.
Now, open the cover and drain the oil. There's about 3 quarts in there.
Next thing I recommend is to break loose the spider gear shaft retaining bolt. It's 6mm I think. Just break it loose. Then drop the driveshaft. It makes it way easier to man handle the carrier.
With the driveshaft down, pull the pin retaining bolt. Roll the carrier up till the opposite end of the pin is pointed up at about a 45 degree angle and peck it out a bit until it is sticking out and not hitting the case. If it hits solid, rotate the carrier farther, its against the pinion. Rotate the carrier and pull the pin. It should come pretty easy once its about half way out. Mine almost fell out when it rolled over. That's because there is no load on it with the clutches worn out.
Push the axles in tight and peck the C clips out with a drift. They should come out pretty easy with the shafts in. Pull the axles out a bit. Use a drift to peck the preload spring out about half way, then roll the carrier over and pull it out with a pair of pliers.
Now pull one axle out. We will use the other one to hold the side gears to roll the spider gears out.
At this point it's a good idea to label a sheet of cardboard or something left and right. You don't really want to swap the gears left and right.
Broom image
This is my helper. He doesn't eat much and is good with working weekends. Hold the axle and rotate the carrier slowly. The spider gears should walk themselves right out. Make sure to get the races with them.
Now you can remove the side gears and clutch packs. Keep them in order so you can see how to put them back. If you don't, that's okay ill show you later but you will need to keep the sides separate to make some measurements.
You should have an empty carrier now.
That's pretty much the tear down. Now get to cleaning. Get all the old oil and crud out you can. Cleaner is always better. It's a good idea while you are in there to look at the wear on the ring gear before you clean it. You can usually see the gear pattern before you clean the nasty off the ring gear. Mine was the correct half moon looking thing centered on the tooth so I am going with it. Probably should check the backlash but I didn't. It was pretty tight so I didn't check it. Those things are really beyond the scope of this article.
Now comes the math portion. I wiped the used clutches, steels, and shim.
You can see the old ones are pretty well shot.
Pic of mic
Using a micrometer squeeze the stack and take a measurement in a few places. (If using a caliper, use a clamp to squeeze the pack which simulates the preload.) It should be pretty close. Take the average if they are pretty close. Write it down. Do the same for the other side. Now add the stack measurement to the axle end play number and in theory, this should tell you what your new stack should be.
Hint: it should be close to 0.650"
A word on the stacking order. Depending on when the unit was produced, it may be stacked a little different. After doing some reading I decided to leave mine stacked the way it came off the side gear. Generally, the best stack is considered to be S-C-S-S-C-S-C-shim. Where C= clutch and S= steel. A google search will explain why this is preferable.
These are the new packs. Notice the order. The side closest to my hand goes against the side gear.
Now take you new clutches and steels (you've been soaking the clutches in gear lube with friction modifier for at least 30 mins now right? If not do it now and have a cold beverage of your choice.), stack them on the side gear to hold them and then lift it off and measure the stack with the 0.035" shim. It's the middle shim. If you are over 0.655" I'd recommend dropping down to the 0.030 shim. If its 0.640" or less, I'd recommend going up to the 0.040" shim. Measure again. If it falls close to your total of about 0.650" stack it back on the side gear. Of course do the same for the other side.
A note on shim thickness. The thickness of the shims basically dictate how "aggressive" the LS is. If you are interested in a very agressive setup, go with a little thicker shim. That being said, you have to balance that with what will fit. If the clutch packs are too tight, you can't install the spider gear pin.
Congrats. You are now ready to start the reassembly process. If you are doing the brakes, I would go ahead and tear that all down. I would go ahead and pull the axle seals too. A pry bar makes quick work of them. Don't install the new ones yet. You may have to take the axles in and out a couple times. Caution: you may get some oil out of the axle tubes when you pull the seals.
Okay. You have cleaned everything. You have measured the clutch packs. Now lets put it back together. Insert the left and right side gears with their clutch packs. Assemble the bolt as shown in the picture.
Bolt pic
Run the nuts up to the head and stick the other washer on and insert it between the side gears.
Spreader pic
Run the nuts out and spread the gears. This will simulate the preload spring and let you install the spider gears.
Slide one axle in until it hits the bolt. Use your helper again to hold the axle. Try to rotate the carrier. If it's stuck, loosen the nuts a little until you can roll it over by hand. Lay the spider gears with the races onto the side gears 180 degrees apart and roll the carrier until the holes line up for the pin to be inserted. It may take a couple tries. I think it took me three. It's easy to be off one tooth either way so that the gears don't line up on the holes at the same time. Pull the spreader bolt out.
Now you should remove the axle and install the seals and whatever brake hardware. Be careful not to rotate the carrier while inserting the axles because the spider gears may fall out. Ask me how I know that.
Now comes the hard part as alluded to by some folks here. The preload spring for the side gears. I messed with this thing for an hour. I tried several different ways to compress it to insert it. I went to the manual and it said to line it up and drive it in with a soft faced hammer. I pecked on it a few times and it just popped back out at me. Eventually, I got irritated and really gave it a good whack with a rubber mallet and damned if it didn't start in. A couple more whacks until I was sure it wasn't coming back out and then we were good.
Clean and install the axles. I put a little gear lube on the seals and axle just for good measure when I insert them.
Push the axles in fully and install the C clips. If the clips don't want to install easily, peck the spring in or out depending until they will. Essentially you are centering the spring. Pull the axles out and make sure the C clips seat in the side gears.
Insert the pin. It should take quite a bit more effort to reinstall it as now the axle shafts should be riding against it. A small hammer and drift should do the job. Try to get the holes for the retaining bolt lined up as close as you can as you insert it to make it easy to insert the retaining bolt. Insert the retaining bolt and torque it to 15-30 ft-lbs or as I did it tight as I could with the 1/4" ratchet. I couldn't get my torque wrench to it. I figure with a range like that it needs to be "tight". It came pre- coated with thread locker.
It should look like this at this point.
Check the axle end play. You should only have a few thousandths of an inch at this point. If its more than that, you may want to re-shim the clutch pack.
Do a quick double check to make sure there are no left out parts and seal it up. I prefer to use a gasket with sealant on either side but some just use RTV. Your preference. I like Permatex stuff. What you use is up to you. Follow their directions.
Reinstall the driveshaft and any remaining brake hardware, throw the tires on and let her down off the stands.
Pull the fill plug and load it up. I took the bottle that I used a portion of to soak the disks and dumped the supplied friction modifier into it to add it. Most of the fully synthetic oils say you don't need the friction modifier but hey... I put it in for good measure.
You should be ready for a test drive. You may hear a good pop the first turn you make as the clutch packs slip for the first time. Try a couple tight turns to make sure the inner wheel isn't kicking then try to make sure both wheels are locking up. I'll let you decide how to do that.
Here is my scientific method.
I wish it were a long smokey burnout video but hey, it's a 4.6 that can't get out of its own way.
Hope you find this helpful. If you spot something wrong or need clarification let me know. Ill try to help.
References
http://youtu.be/0GsLDg3C6Hc
Good discussion on clutch pack assembly. This guy has a couple videos on the 8.8.
Ford light truck service manual 1983 model year
Standard disclaimers. I'm not responsible for your stuff and don't hurt yourself.
Vehicle: 2001 Ford F150 SCab with 8.8 rear diff. This diff is common to a lot of vehicles over a couple decades.
Motivation:
My rear diff was making a little noise and on inspection, I realized that the noise was coming from the right rear. It actually was a brake noise resulting from the axle end play binding the brakes. After a little research I determined in all likelihood the culprit was worn clutch packs in the limited slip unit.
What you need other than the parts:
Dial gauge, micrometer or caliper, basic hand tools, 0.5" bolt 2.5" long with a pair of 1.5" diameter and low profile (thin) nuts.
With the truck up on stands, take the wheels and brake rotors or drums off. I put the dial gauge on the axles (both sides) and measured the end play.
You must be registered for see images attach
Axle measure pic
Right side was 0.101" and the left was 0.025". I haven't found a spec from a reliable source for this number but I have seen 0.030" tossed out as a max number. This is pretty reasonable considering what I found inside. More on that later.
So I ordered a rebuild kit from Amazon (~$83). I should mention at this point, if you've never done the rear brakes (mine is 2001 with 125k miles and it was all original) this is a great time to do pads rotors and e brake shoes. All of that came from Advance ($150 with 15% off). That also included 3 quarts of Royal Purple 75W 140 ($20 per quart less the 15%). I also picked up new axle seals because it seemed silly to not change them while it was apart. About $28 for them less the core charge.
Now, open the cover and drain the oil. There's about 3 quarts in there.
Next thing I recommend is to break loose the spider gear shaft retaining bolt. It's 6mm I think. Just break it loose. Then drop the driveshaft. It makes it way easier to man handle the carrier.
With the driveshaft down, pull the pin retaining bolt. Roll the carrier up till the opposite end of the pin is pointed up at about a 45 degree angle and peck it out a bit until it is sticking out and not hitting the case. If it hits solid, rotate the carrier farther, its against the pinion. Rotate the carrier and pull the pin. It should come pretty easy once its about half way out. Mine almost fell out when it rolled over. That's because there is no load on it with the clutches worn out.
Push the axles in tight and peck the C clips out with a drift. They should come out pretty easy with the shafts in. Pull the axles out a bit. Use a drift to peck the preload spring out about half way, then roll the carrier over and pull it out with a pair of pliers.
Now pull one axle out. We will use the other one to hold the side gears to roll the spider gears out.
At this point it's a good idea to label a sheet of cardboard or something left and right. You don't really want to swap the gears left and right.
You must be registered for see images attach
Broom image
This is my helper. He doesn't eat much and is good with working weekends. Hold the axle and rotate the carrier slowly. The spider gears should walk themselves right out. Make sure to get the races with them.
Now you can remove the side gears and clutch packs. Keep them in order so you can see how to put them back. If you don't, that's okay ill show you later but you will need to keep the sides separate to make some measurements.
You should have an empty carrier now.
You must be registered for see images attach
That's pretty much the tear down. Now get to cleaning. Get all the old oil and crud out you can. Cleaner is always better. It's a good idea while you are in there to look at the wear on the ring gear before you clean it. You can usually see the gear pattern before you clean the nasty off the ring gear. Mine was the correct half moon looking thing centered on the tooth so I am going with it. Probably should check the backlash but I didn't. It was pretty tight so I didn't check it. Those things are really beyond the scope of this article.
Now comes the math portion. I wiped the used clutches, steels, and shim.
You must be registered for see images attach
You can see the old ones are pretty well shot.
You must be registered for see images attach
Pic of mic
Using a micrometer squeeze the stack and take a measurement in a few places. (If using a caliper, use a clamp to squeeze the pack which simulates the preload.) It should be pretty close. Take the average if they are pretty close. Write it down. Do the same for the other side. Now add the stack measurement to the axle end play number and in theory, this should tell you what your new stack should be.
Hint: it should be close to 0.650"
A word on the stacking order. Depending on when the unit was produced, it may be stacked a little different. After doing some reading I decided to leave mine stacked the way it came off the side gear. Generally, the best stack is considered to be S-C-S-S-C-S-C-shim. Where C= clutch and S= steel. A google search will explain why this is preferable.
You must be registered for see images attach
You must be registered for see images attach
These are the new packs. Notice the order. The side closest to my hand goes against the side gear.
Now take you new clutches and steels (you've been soaking the clutches in gear lube with friction modifier for at least 30 mins now right? If not do it now and have a cold beverage of your choice.), stack them on the side gear to hold them and then lift it off and measure the stack with the 0.035" shim. It's the middle shim. If you are over 0.655" I'd recommend dropping down to the 0.030 shim. If its 0.640" or less, I'd recommend going up to the 0.040" shim. Measure again. If it falls close to your total of about 0.650" stack it back on the side gear. Of course do the same for the other side.
A note on shim thickness. The thickness of the shims basically dictate how "aggressive" the LS is. If you are interested in a very agressive setup, go with a little thicker shim. That being said, you have to balance that with what will fit. If the clutch packs are too tight, you can't install the spider gear pin.
Congrats. You are now ready to start the reassembly process. If you are doing the brakes, I would go ahead and tear that all down. I would go ahead and pull the axle seals too. A pry bar makes quick work of them. Don't install the new ones yet. You may have to take the axles in and out a couple times. Caution: you may get some oil out of the axle tubes when you pull the seals.
Okay. You have cleaned everything. You have measured the clutch packs. Now lets put it back together. Insert the left and right side gears with their clutch packs. Assemble the bolt as shown in the picture.
You must be registered for see images attach
Bolt pic
Run the nuts up to the head and stick the other washer on and insert it between the side gears.
You must be registered for see images attach
Spreader pic
Run the nuts out and spread the gears. This will simulate the preload spring and let you install the spider gears.
Slide one axle in until it hits the bolt. Use your helper again to hold the axle. Try to rotate the carrier. If it's stuck, loosen the nuts a little until you can roll it over by hand. Lay the spider gears with the races onto the side gears 180 degrees apart and roll the carrier until the holes line up for the pin to be inserted. It may take a couple tries. I think it took me three. It's easy to be off one tooth either way so that the gears don't line up on the holes at the same time. Pull the spreader bolt out.
Now you should remove the axle and install the seals and whatever brake hardware. Be careful not to rotate the carrier while inserting the axles because the spider gears may fall out. Ask me how I know that.
Now comes the hard part as alluded to by some folks here. The preload spring for the side gears. I messed with this thing for an hour. I tried several different ways to compress it to insert it. I went to the manual and it said to line it up and drive it in with a soft faced hammer. I pecked on it a few times and it just popped back out at me. Eventually, I got irritated and really gave it a good whack with a rubber mallet and damned if it didn't start in. A couple more whacks until I was sure it wasn't coming back out and then we were good.
Clean and install the axles. I put a little gear lube on the seals and axle just for good measure when I insert them.
You must be registered for see images attach
Push the axles in fully and install the C clips. If the clips don't want to install easily, peck the spring in or out depending until they will. Essentially you are centering the spring. Pull the axles out and make sure the C clips seat in the side gears.
Insert the pin. It should take quite a bit more effort to reinstall it as now the axle shafts should be riding against it. A small hammer and drift should do the job. Try to get the holes for the retaining bolt lined up as close as you can as you insert it to make it easy to insert the retaining bolt. Insert the retaining bolt and torque it to 15-30 ft-lbs or as I did it tight as I could with the 1/4" ratchet. I couldn't get my torque wrench to it. I figure with a range like that it needs to be "tight". It came pre- coated with thread locker.
It should look like this at this point.
You must be registered for see images attach
Check the axle end play. You should only have a few thousandths of an inch at this point. If its more than that, you may want to re-shim the clutch pack.
You must be registered for see images attach
Do a quick double check to make sure there are no left out parts and seal it up. I prefer to use a gasket with sealant on either side but some just use RTV. Your preference. I like Permatex stuff. What you use is up to you. Follow their directions.
Reinstall the driveshaft and any remaining brake hardware, throw the tires on and let her down off the stands.
Pull the fill plug and load it up. I took the bottle that I used a portion of to soak the disks and dumped the supplied friction modifier into it to add it. Most of the fully synthetic oils say you don't need the friction modifier but hey... I put it in for good measure.
You should be ready for a test drive. You may hear a good pop the first turn you make as the clutch packs slip for the first time. Try a couple tight turns to make sure the inner wheel isn't kicking then try to make sure both wheels are locking up. I'll let you decide how to do that.
Here is my scientific method.
You must be registered for see images attach
I wish it were a long smokey burnout video but hey, it's a 4.6 that can't get out of its own way.
Hope you find this helpful. If you spot something wrong or need clarification let me know. Ill try to help.
References
http://youtu.be/0GsLDg3C6Hc
Good discussion on clutch pack assembly. This guy has a couple videos on the 8.8.
Ford light truck service manual 1983 model year
Last edited:
