How to Rebuild our Differential and Torque TubeSTEP BY STEP WITH PHOTOS
Posted 05 July 2012 - 11:56 AM
Please note: I am not a mechanic who works on cars day in and day out! I don't have an unlimited supply of specially tooling! I am an auto enthusiest/backyard mechanic like the majority of us on this site. I've done my best to document how I performed this particular rebuild using standard hand tools and the factory service manuals as my guideline. If you see something in error, please respond via PM. If you see something that may be performed in a simpler fashion, again please respond.
Background: This particular rebuild was to freshen up a stock 88/89 differential. The differential shown in the 'assembly' portion of this thread was pulled from a junkyard over 15 years ago...from a low mileage car. It was disassembled over 10 years ago and placed in storage. The 'disassembly' portion of this thread consists of an 87 differential from one of my former daily drivers that is shot (and I'll prove it in this thread)....I simply took it apart to gather parts (shims), make a tool , and photograph the disassembly for creation of this thread.
For the assembly, I retained the stock gear ratio ring/pinion in its original carrier. However several 'new'/'borrowed' parts were used on the rebuild including the spline coupler, shims, etc. However, the steps in this thread are applicable for gear ratio swaps...I'll try to differentiate what additional steps would be required during the writeup if you were swapping internals (new ring/pinion) to the carrier.
First and foremost: YOU NEED THE FACTORY MANUALS! If you do not have the factory manuals, get them. They are downloadable on several starquest sites and are also on ebay constantly for a very low price.
Parts required: Please follow the thread to list the required parts for this rebuild. At a minimum you will need all new bearings and seals. You may need the appropriate shim kits, as req'd, during the rebuild. Follow along to determine what you will need and why.
Tooling Req'd: This rebuild required several specialty tools including even custom made tooling. Read thru the write-up to determine what tooling you will need to perform your rebuild. A variety of pullers will be required at a minimum, see the photos on the pullers I used and make a determination on what you will need as a result. There are many different ways to skin a cat in terms of removing the old bearings/seals. If you have access to a shop press, then you will be best off. I mixed the use of a shop press and several different (even homemade) puller types for this particular rebuild. Note: I've also literally cut bearings off with a dremel tool in the past - obviously you need to be very carefull you don't cut thru the bearing and into the pinion or gear carrier if you go this route.
IMPORTANT: Note the LACK of air tool usage in this rebuild! I own a very high cfm compressor and high torque impact drivers. I did NOT use any of these tools on the differential rebuild, even during disassembly! The differential is one of the most important parts of a vehicle's drivetrain. Care is to be taken during it's rebuild. I don't like the unpredictable response of impact guns. Don't get me wrong, impact guns have their purpose but not for rebuilding a rear differential. This rebuild is conducted with the aide of hydraulics and lever arms - both providing a smooth and controllable method of assembling or disassembling a joint.
Edit 11/5/2014: Lately I have been receiving many requests from club members asking if I would consider rebuilding their parts per the steps shown in these ‘how-to’ threads. Although I am humbled at your trust in my abilities to rebuild such critical parts of your vehicle, I respectively have to decline any such requests. With a family of four, a demanding career, and just the normal responsibilities in everyday life, I have difficulty in finding time to work on my own project vehicles much less take on additional work. However, I encourage you to review the thread in detail, try to gather the required parts and tools, and attempt to rebuild the items on your own. My goal in developing these threads was to give members the encouragement to perform these component rebuilds at home while gaining valuable experience, saving some $, and simply having fun with the hobby. I hope by sharing this information and by including my own trials and mistakes along the way, help to achieve these goals.
Posted 06 July 2012 - 10:30 AM
Note: Again this is the disassembly of an old/trashed 87 differential/torque tube out of one of my former daily drivers. I'm pulling it apart here simply to develop this thread and obtain a few spare parts.
Step 1: I'm starting with a differental that has been removed from the vehicle and the torque tube unbolted. First and foremost is to clean your parts! There is no reason to introduce all of those contaminates into the closed system. Even though we are fully tearing down, why risk getting debris stuck back in the crevises of the carrier? Simply clean off the outside of the carrier with mineral spirits and a wire brush prior to starting the tear-down.
Note: The parts washer above only costs about $30 and has ~ 3 gallons of mineral spirits in it. If you don't own a parts washer, purchase one. The cost of solvent you waste without having one will easily offset the price of a washer.
I don't show the cleaning of the parts during the disassembly. I believe that goes without being stated. Once you have the rear torn down, use the parts washer above to thouroughly clean each individual part prior to assembly.
Next: Torque Tube Disassembly
I took an old piece of slotted hole angle iron I had laying around and bolted it to the flange of the torque tube. This acts as a lever arm for breaking free the main nut.
Using a center punch, make match marks on the flange and torque tube for reassembly:
Remove the flange using a dampener puller.
Then remove the C clip using internal snap ring pliers with the proper tips.
Tap the TT itself with a rubber mallet to remove it from the TT carrier. The bearing will stay in the TT carrier. Sorry forgot to snap a pic of this.
Now remove the ball bearing. See the makeshift puller that I rigged up consisting of a socket, extension, and balancer puller. Note the sideloading of the bolts...not the best setup but this bearing isn't press fit tightly into the carrier so the load to press it out is minimal. Note: You could just tap the bearing out with a hammer but I prefer the controlled fashion of removing bearings.
Now to clean and inspect your parts.
From inspection of the TT spline, you can see that this particular TT is shot! The wear is the same on the spline coupling of the differential.
This specific TT is to be trashed....actually it is going to be turned into a tool!! Perfect option for a spline wrench to hold the spline of the differential during rebuild. I simply cut off the end of the TT and welded a restraint bar onto it.
Tool mated to an old spline nut.
Without the aide of this homemade tool, I'm not sure how I would have properally restored this differrential. I've tried the channel lock method...only to destroy a spline coupler as a result. I urge you to find and old TT like this and develop this tool.
Posted 06 July 2012 - 11:34 AM
Step 1: To properly rebuild the differential, you should have some sort of a stand. Using some old flat bar that I had, I welded up a stand using the cartoon in the FSM as a guide. This stand not only serves as a good method of holding the differential, it is also a good base for the mag base of your dial caliper as well as a method of reacting from with removing/installing the pinion nut.
Forgot to mention that you need to remove the differential cover..but I think that goes without being said.
OK...before disassembling any of the internals of the differential, take the time to inspect your starting point. It isn't worth rebuilding the entire rear only to find out that your pinion/ring is shot in the first place. This particular rear is shot...and I'll prove it in the pictures below. I would not use this ring or pinion on my rebuild...but the carrier could be retained.
Note: The FSM says the same thing as I describe, perform these inspections prior to teardown.
First: Drive Gear Runout. This is a check to make sure the drive gear is perpendicular to the axis of the output shafts. If this failed, the ring itself isn't mounted flat to the differential case or the differential case isn't sitting square in the carrier. Note: due to the tip of my cheapo dial indicator, I couldn't get a nice straight shot at the backside of the drive gear. I had to angle it. This isn't the best method because it could give me a false indication due to the compound angle, but it did the job in telling me that everything was square. I had a fraction of a mil of runout from this test and the limit is .002
You want the tip of the indicator touching the back side of the drive gear as close to perpendicular as you can get it. Spin the drive gear 360 degrees and note the maximum runout.
Runout checks out ok. Now for backlash.
Mount your dial indicator about 2/3's up the tooth of the carrier (note that in this photo, my indicator was near the outer edge of the tooth...I typically like to get it just past the center when doing final backlash checks). Try to align it perpendicular to the cut on the tooth.
Hold the pinion nut. I simply used my spline wrench tool braced on the side of my stand to hold the pinion as I rocked the gear back and forth taking note on the backlash.
Repeat on the other side of the drive gear tooth.
Perform these two backlash tests on 2-3 teeth along the circumference of the drive gear. Take the average to determine your backlash. The value should be within .005-.007 inch. This particular rear had up to .015! Further reason on why it is trashed. I forgot to do a closeup of the teeth but you can actually see the wear on them.
Next check: Pinion runout.
Mount your indicator as shown and spin the gear..in turn spins the pinion...to check your pinion runout. The limit is .004 inch. I had less than one mil. Note: I used the turned down area of the spline coupler rather than the spline itself as shown in the manual. Upon assembly, I do both tests...but this pre-test told me there isn't an issue in terms of pinion runout.
Last check: Contact Pattern.
For this check, I used some prussian blue. NOTE: THIS IS THE LAST TIME I EVER USE PRUSSIAN BLUE...IT SUCKS!! See the new marking compound that I now use in the assembly section of this thread.
Anyways, apply the compound, spin the carrier back and forth while providing a little bit of resistance with your palm on the pinion spline. Spin back and inspect your results.
You can kinda see the pattern using the prussian blue and it actually doesn't look too bad considering the wear of the gear. I'm not spending too much more time here. I know this rear is shot, so I'm moving on. For yours, use the GM compound shown later on and make a better determination on how your differential stands prior to rebuild.
Note: Just because you fail some tests above doesn't mean your rear is shot. Make your own determination. Mine was compounded with the spline joint wear, visible wear on the teeth, and horrible backlash that made me junk this pinion/gear.
Posted 06 July 2012 - 12:15 PM
Crack free and remove the four bolts holding the differential case in the carrier
Remove the bearing caps and MARK THEM LH/RH!!! <-- VERY IMPORTANT STEP!!!!!
Using a pry bar and block, remove the differential case assembly.
The shims and outer bearings will come free in this step. Don't mix them up. Label each LH/RH.
I seperated mine into two bins as shown and labeled the bins and parts.
Here is what you should see now:
Only the pinion left...as if it were really that easy...we haven't removed any bearings yet, lol
Using a 30mm socket, breaker bar, the base, and my new little spline tool, Crack free and remove the pinion nut.
Matchmark your coupling nut to your pinion using the punch. If you end up swapping pinions (higher ratio or whatever) don't worry about performing this step, I'll explain later how to reinstall and verify it is on correctly without the matchmarks.
Using a three jaw puller, remove the spline coupler.
Tap out the pinion with a rubber mallet
Here is what you should have out of the carrier now. Don't mix up the order of your components or loose that pinion crush shim(s) <-- yes you may have one or more shims there.
Next, knock out your old seals on the output of your carrier. You can use a seal puller, but i just tapped them out with the screwdriver/mallet.
Look down your carrier to see what is left of the pinion assembly. you'll see two outer bearing races, an oil seal, and the inner race of the pinion bearing. Note the ledges of the cast carrier. This is what is used to tap out the outer bearing races.
Pull the oil seal. The inner bearing that is just laying in the carrier will fall out. Use a 1/2" rod (I used steel, but if you have a brass or aluminum it would be better in that if you did hit the carrier, you woul have less chance of cracking it). Take your time in driving out the races, they come out fairly easy but I tapped a few times on one side, moved the bar 180 degrees, tapped more, etc etc until they pop out.
Now the hard parts (removing the inner bearing races from the differential case and pinion).
First up. Differential pinion. I used a bearing puller to 'grab' under the bearing. However it will still deform the 'cage' upon removal. I broke my large spreader on a differrent project so I used a shop press. (A good friend of mine owns a fab shop, so I took advantage of it). Remove the inner bearing and DON'T LOOSE THE SHIMS!
Sorry didn't realize the photo was sideways when I downloaded it.
Next (gear bearings):
I simply cut off the cages of these two bearings prior to removing them. This gave me access for my puller.
Using a 2 jaw puller, remove the bearings.
Well that is about it. Everything is apart. Take your time cleaning up all of your components and prepping for assembly. Note: I was not swapping pinion/gears for my assembly so I didn't need to remove the gear from the differential case assembly. But this is straightforward if you need to remove it (just remove the bolts).
Also note: This rebuild doesn't consider rebuilding the clutch packs. I have yet to have a clutch pack failure in a CQ differential...so I simply didn't take this assembly apart. I just took my time in cleaning the differential case assembly.
Posted 06 July 2012 - 12:40 PM
Note: Again this is an 88/89 rear differential removed from a low mileage car in a junkyard over 15 years ago. In fact, I disassembled it (pretty much the same way I already described but in a little more crude of a fashion) over 10 years ago and put it in storage.
Again...take your time in cleaning all components using mineral spirits, brushes, etc. Thoroughly dry everything and lay it out. This is the perfect time to clean up your carrier/TT carrier and paint them. The items you see here were bead blasted, powdercoated, and clear coated (overkill, I know but this particular rear is going in a car that I have been building for almost 12 years).
Also clean up that gasket surface now that everything is apart. Don't leave that for later.
I always have my FSM and parts sheets handly on any rebuild of a CQ part.
Measure all the shims that you took off and record:
New Pinion Bearings:
I bought all new pinion bearings and oil seals from advance auto. Most are 'National' brand.
Sorry for the glare (cheap camera). See the zoom in's below:
Cup and Bearing for Inner Pinion (National HM89410 and HM89449)
Cup and Bearing for Outer Pinion (National M88010 and M88043)
Pinion oil seal (National P/N 224570)
Torque Tube Bearing:
I'll show the gear bearings/seals later on when we get there. Lets focus on just the pinion for now (the hardest and most time consuming part)
I did go ahead and purchase both inner and outer pinion shims from Mitsubishi. However I only used the inner shim kit....will talk about more later.
Torque Tube Assembly
Lets start with the torque tube assembly...the easiest...and get it out of the way.
Install the TT bearing, National 206FF, using the appropriate size bearing driver.
Drive it flush with the flange. You will see the notch for the C-clip.
Insall the C clip with your internal snap ring pliers...with appropriate size tips for the C clip
I like to grease up the bearing really good...even though this is a sealed bearing. I didn't show it, but I also greased up the full Torque Tube prior to placing in the carrier...this prevents corrosion down the road.
Install the torque tube, the flange (mated to your matchmarks...remember those?), washer, and nut. Bolt back on your angle iron and torque to factory specifications: 116-159 ft-lbs
Torque Tube rebuild done....for now. We'll revisit it when the differential is complete.
Posted 06 July 2012 - 12:55 PM
I always tap every thread when I'm rebuilding something. It is a good time to get this done early on. Why introduce more contaminates to the system.
Don't forget about the four tapped holes in the differential for the bearing caps (forgot to show a pic of them).
Cover placed over hole to prevent foreign material from entering the differential.
Bearing Cup installation.
Prior to mounting the carrier in the stand, I installed both pinion bearing cups. I always put a little 3in1 oil on the bare steel for installation....probably overkill but I like to have a very thin lubrication layer when press fitting something. Others may argue different but I firmly believe it helps more than harms.
Use approprite bearing driver and install the cones. I started with a mallet but had to switch to a hammer to install these.
Use an inspection mirror to verify the cones are fully seated <--- I CONSIDER THIS A VERY IMPORTANT STEP
You want those cones flush (metal-to metal) with the flanges. If they are not, you WILL have problems with pinion assembly.
Now mount the differential in your stand.
Posted 06 July 2012 - 01:01 PM
But if you are swapping internals or gear ratios, you need to make a decision. I fully believe that a good starting point is to use the appropriate shims for the CARRIER...and NOT the donor pinion. Reason being is that the pinion itself is lathe cut...which can be held to a very tight tolerance. The carrier is cast iron and then machined internally for the bearing cones. There is less chance of the carrier meeting as tight of a tolerance as the lathe cut pinion. I'd strongly suggest starting with the pinion height shim of your CARRIER and go from there. What sucks is that you won't know that you did it right until you fully assemble....which means you may have to fully tear down again to adjust. Now the FSM uses some mockups to help in shim selection....good luck in finding those....would be an easy task if you had a ford 9" or something, but not a CQ rear. But make your own determination. My choice was easy...start with what I took off.
I took advantage of my buddy's shop again and used his press to press on the pinion bearing. DON'T FORGET YOUR SHIMS!!!! You will be pissed if you do!
Ok now, I took a little gear oil. I'm not concerned on the viscosty/type/etc now. I'm just putting a little on the bearings to aide in assembly.
Next, install the factory spacer. NOTE: Did you know that there are two differrent length factory spacers? Well there are! Keep the stock spacer for your pinion and/or carrier and go from there.
Sorry for the fuzzy pic
Now for the next shim...the pinion crush shim. Well I kept the original carrier and original pinion/gear...so it should be the original shim right? I wish it were...I wasn't so lucky. However start with the original shim for your pinion.
Apply some grease over the spline of the pinion.
Rotate the carrier to horizontal (your stand will help). Install the pinion assembly from inside.
Install some gear oil on the brand new outer pinion bearing.
Install the bearing, the spline coupler, washer, and nut. DO NOT INSTALL THE OIL SEAL YET <----VERY VERY VERY IMPORTANT
Using your homemade tool and a torque wrench, torque the pinion nute to factory specifications: 137-181 ft-lbs
Now using an in-lb torque wrench, measure the starting torque of your pinion system. I bought this little wrench from amazon for $40
The starting torque with NO oil seal should be 1.3-2.2 in-lbs
Want to know what mine was? Try 30 in-lbs!!!! Bad news. My shim is too small. Time to take her apart.
Untorque your pinion nut, pull the spline coupline with the 3 jaw puller again and tap out the pinion.
I remeasured my original shim.
I opened up my pinion crush shim kit and measured and recorded every thickness:
Posted 06 July 2012 - 01:30 PM
Result: still way too high! over 20 in-lbs starting torque.
So I iterated, one mil at a time until I hit my target. Keep tearing it down and redoing it with .001 thicker shim each time. Don't jump on up high in size...you want to hit that point where it is the perfect balance between too tight and in spec.
Took me FIVE iterations until I was comfortable. After the 3rd try I was pretty confident I got it...but I experimented with a different combo on the forth try to split the difference by .0005" to see if it helped. Ended up going back to the 3rd combo for my final effort.
keep good notes and make your best determination of what combo works. In all honesty, you can do these iterations without the in-lbs torque wrench. You can easily feel when it is too tight. When you hit that perfect clearance, the pinion will spin with ease. One mil less and it is tight as heck.
Now tear it back down. I know, I know,,sucks but it is important.
Install your bearing again. Relube as required
Now install your oil seal. My seal drivers didn't work on this replacement seal...so I carefully tapped it in using a wooden dowel.
Grease up your seal and re-grease your spline.
Reinstall for what hopefully is the last time.
Now check your start-up torque with the oil seal installed. It should be between 3.5-4.3 in-lbs
And it was!
Now I'm going to check my pinion runout again. Same method as before.
And again on the spline
And mine was good...less than .004. If you fail this, try removing the spline coupling, flipping it 180 degrees and reinstalling. Also a good trick if you didn't have yours matchmarked. Keep turning the coupler on the pinion shaft until you meet specification. If you still don't meet spec, something is horribly wrong (bad bearing, non-seated bearing, cracked carrier, etc etc)
Posted 06 July 2012 - 01:39 PM
Now your need your gear bearings and seals (National KC-11445-Y and National 471847N). These bearings come together with both the bearings and cups. DON"T MIX THEM UP!!!
Applying my 3in1
Using the appropriate size bearing driver...install both bearings.
Store your cones appropriately for now (note they are labeled)
Used the cone side of my bearing press to start them on.
And flipped it over flat to drive them home.
inspect and make sure they are fully pressed on.
Now put a little gear oil on both bearings.
Posted 06 July 2012 - 01:43 PM
Again...same carrier...same ring/pinion....ie should be the same shims. How can I be wrong again, lol. But still always start with the ones you took out!
With the differential case assembly, bearing cones (on proper sides), and shims...install as one unit.
Tap the assembly down.
Verify it is down
Install caps (make sure they are on the correct sides...remember you marked them earlier?)
Posted 06 July 2012 - 01:53 PM
Same process are before....both sides of a gear tooth...keep your indication 2/3's up the tooth and perpendicular to the tooth face. Perform on three different teeth along the circumference of the ring.
it met spec.....005-.007 in! Good news...but not done yet.
Now to check contact pattern. This time I used the good stuff. YOU MUST USE THIS COMPOUND....IT IS THE BEST!!
Apply it as before.
Spin the gear until it contacts the pinion and then apply a small load with your palm on the pinion coupler while rotating the ring back and forth. Spin it back and check it out.
ITERATION #1: NOT A GOOD PATTERN
DAMN-IT!!! Not a very good pattern..note that it is high on one side and low on the other.
Well my shims were .126 and .122 for LH/RH respectively. I'm going to flip them...maybe I screwed up with my labeling? Good thought but doubt it...still going to try.
Remove the differential case assembly and flip the shims...reinstall....check backlash...check contact pattern.
Here is the pattern now.
ITERATION #2: NOT A GOOD PATTERN
Still don't like it. Plus my backlash exceeded the limit.
So now what....well how about splitting the difference in shim size. This actually means go with and equal size shim set at .124
I just so happen to have two shims of that size in my spare parts bin. Again disassemble/reassemble, check pattern, and backlash.
ITERATION #3: A GOOD PATTERN!!!!!
Check out that pattern!!! That is about as perfect as I could ask for!
it took 3 iterations:
Posted 06 July 2012 - 02:03 PM
I don't show this pictorally...but i did go back and check my contact pattern and backlash on three areas around the ring after torquing...everything SAT.
Last but not least....check my gear runout. Note: If you installed a new gear during the rebuild, you may have to swap phase to meet specification. I didn't have to do this because I never removed the ring. I simply just checked the runout again and verified it was in spec (I know, I know,,,its a crappy angle but it told me the story)
NOTE: IF YOU REMOVED YOUR RING FROM THE DIFFERENTIAL CASE ASSEMBLY...MAKE SURE YOUR APPLY THE APPROPRIATE LOCKTITE AND TORQUE THE RING DURING ASSEMBLY. It is very common for these bolts to spin out
Posted 06 July 2012 - 02:46 PM
Now for the cover.
I looked everywhere for the factory gasket...no luck! I even ordered one from rockauto and it wasn't correct. So I made one. Using gasket material, punches, and scissors/exacto.
Used red scotchbrite to 'scuff' up the gasket for a good bite.
Finally removed the differential from the stand.
Cleaned up the gasket surface on the cover.
I totally forgot to tap the cover bolt holes earlier. I don't like doing this at this stage but it needed done. Do this earlier prior to assembly. Looking back, I should have covered the internals while I was tapping...way too easy to get debris in the carrier.
REMEMBER....KEEP YOUR WORKPLACE CLEAN!! DUST/DIRT IS THE NUMBER ONE KILLER OF INTERNAL DRIVETRAIN COMPONENTS.
Final wipedown with acetone (cover and carrier)
Laying a nice consistent bead.
Place gasket on cover
Permatex on carrier. Probably a little overkill here.
This is the only time that I don't care about appearance...lol...I want this rear to be leaktite. I ran a bead around the perimeter once it was torqued.
Posted 06 July 2012 - 02:51 PM
Open it up like this and make sure it is cleaned out good.
Close it up
Apply the permatex...don't get it anywhere near the air vent!
Grease up the spline joint on both ends really really good
Grease the seals.
Now if it is going to be a little bit until the rear is installed, use a piece of household seran wrap to cover the holes
Well there you have it! Bolt her together.
Combined with OEM TT mounts, Stedebani rear mounts, and some new hardware....she is ready to install.
Posted 06 July 2012 - 02:56 PM
Note: It took me 6 weeks to rebuild this differential!! That was working on it a few nights a week. It is very time consuming and very frustrating. And should I mention; very expensive (bearings, shims, seals)
Sorry for the length of this thread...it could have been simplified drastically...but wanted to capture as much detail as I could. If you are planning on rebuilding your differential, print this thread out, study it and compare it to the FSM prior to starting.
Good luck in your rebuild. Please let me know if there is anything that I missed or have in error. I'm curious to hear other's experience and tricks.
Next to come: Axle Rebuild
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