The Top DSM Community on the Web

For 1990-1999 Mitsubishi Eclipse, Eagle Talon, Plymouth Laser, and Galant VR-4 Owners. Log in to remove most ads.

Please Support Fuel Injector Clinic
Please Support Morrison Fabrication

1G 1990 AWD Rear Differential Inspection and Replacement

I have been tracking down a horrible grinding noise on decel. I started to notice this noise after all the rear subframe work and rebuilding the driveshaft. Now that all of this was new and in good working order, the noise leads me to the rear differential. I started reading the manual and found that there was an easy test to check the total backlash of the diff. When I performed this check I got a .5 inch of backlash. The Service limit is .2 inches, sssooooo I have somehow obtained 2.5 times the amount of acceptable backlash. With this information and an angry tiger in my hatch on decal, I embarked on this next adventure of going through the rear differential. This particular rear is 3bolt LSD out of a 1990 AWD Talon.

When working on the rear, I find it easier to remove the whole subframe. Yes you can remove just the rear and axles, but I am going to drop the whole subframe. Start by draining the rear diff and catching all the fluid to examine for metal chunks. Support the car as high as possible on jack stands. Getting the car high is the key to being able to clear the gas tank once the subframe is down. Remove the tires, e-brake cable, and calipers. Attach the calipers to the shock via a zip tie or other material to prevent brake line damage.

Remove the exhaust and be careful not to scratch your expensive pieces of tubing.

You must be logged in to view this image or video.


Note: There are very few bolts that hold the subframe in, so you will want to support the diff via a floor jack and be prepared to balance the assembly with your free hand once it is loose.

Remove the lower shock absorber bolts.

You must be logged in to view this image or video.


Remove the 10mm brake line bolt that is easily accessible.

You must be logged in to view this image or video.


Do not forget about the 10mm bolt holding the brake line from the top. This bolt is not easily accessible and can be removed later, BUT you must remember this bolt or your subframe will be dangling by your e-brake cable.

You must be logged in to view this image or video.


Make mating marks on the drive shaft and the pinion flange. Then remove the four bolts and separate the driveshaft from the pinion flange.

You must be logged in to view this image or video.


This is a good time to test your LSD if you have one. Slowly rotate one tire in a forward motion and the tire on the opposite side should move in the same direction. If it does that is one test down, If it does not, then that starts to point a finger at the LSD. This test can also be referenced in the FSM. Also in this picture, you can see where I made the marks to measure the backlash of the rear diff.

The bolt on the right in this next picture should be removed first. There is one of these on each side.

You must be logged in to view this image or video.


Now there are only four bolts left holding the subframe on. IF YOU HAVE NOT SUPPORTED THE SUBFRAME YOU NEED TO DO IT NOW. The nut on the left in the picture above holds the front portion of the subframe on. There is also one of these on each side.

The last two nuts are for the differential support.

You must be logged in to view this image or video.


Once these are out, your subframe will be free. You will now need to remember about those upper e-brake cable bolts if you did not remove them before. Also, be aware that the sway bar will catch the drive shaft!!!!! The trick is to lower the subframe just enough to clear the mounting bolts, then slide it towards the gas tank. Then, while balancing the subframe with one hand, push the driveshaft towards the transfer case to clear the rear sway bar. After the driveshaft is clear, you just have to wiggle the subframe and pull it out on your rolling jack. This is of course easier said than done.

Now removing the diff is quite simple. Remove the 6 axle nuts (3 on each side for this 3 bolt). To separate the axle from the cup, use a metallic (metal) hammer. TAP on the cup while pulling on the axle and the shock from the hammer will make them separate. Now that you have both axles separated, you can remove the two side bolts holding the diff in. The bolt is already taken out in this picture, but gives a reference of how to find it.

You must be logged in to view this image or video.


This access hole is between the lower and upper control arms.

Now remove the two upper bolts holding the diff in.

You must be logged in to view this image or video.


Now the differential will be loose. If it is still on the jack, just roll it out. Be sure to support the rest of the subframe when removing the diff.

You must be logged in to view this image or video.


Now you will need to separate the axles. It may have been smarter to do this with the diff still bolted up to the subframe, but as you can see I did not. Get your favorite pry bar and place it as shown in the next picture. Apply some pressure to avoid slippage and give the pry bar a good whack with your free hand. This will pop the retaining clip loose so that you can remove the axles.

You must be logged in to view this image or video.


You must be logged in to view this image or video.


Take your axels and store them to avoid damage. Tape the splines as a precautionary measure with masking tape.

You must be logged in to view this image or video.


Now the fun begins 

Start by placing the diff inside of your vice. This is not the most conventional way as they do make a stand to hold differentials, but not everyone is going to have that special tool, so the next best thing is a vice with some cardboard spacers to prevent case damage. Also, make sure if you use the vice that you have it locked down nice and tight. Any time you are using a hammer, be sure to check the diff every few whacks. IF YOU DO NOT THE DIFF COULD FALL OUT OF THE VISE!!!!! Ask me how I know 

You must be logged in to view this image or video.


Start by removing the 14mm outer case bolts.

You must be logged in to view this image or video.


The cover will be sealed on and will not just lift off. Grab your hammer and a punch. There are two holes that go through the diff housing where you can insert the punch to push on the back side of the diff cover. This makes easy work of removing the cover.

You must be logged in to view this image or video.


You will end up with something like this. YUM!!!!

You must be logged in to view this image or video.


You must be logged in to view this image or video.


After the cover is off, you will need to start a battery of test. The first one I chose was drive gear run out. The Service Limit for run out on the Ring Gear is .002 of an inch. You will need a magnetic base of some kind, a dial gauge good to at least a .001 and some patience. Clean the surface where you plan to make your measurement to insure accuracy. Setup the dial gauge so that it is as close as possible to 90* of the part you are measuring. On my gear there was a shoulder that was perfect for the task.

You must be logged in to view this image or video.


You must be logged in to view this image or video.
 
Last edited by a moderator:

BoostedBeaver

Moderator
950
252
Aug 15, 2009
Augusta, Georgia
Now rotate the pinion and watch the dial gauge. Make a few rotations if necessary until you see the points of max and min. It does not have to be zeroed out on the gauge; you just need to know how much is between the max and min points. For picture purposes, my gauge was zeroed to show total run out.

You must be logged in to view this image or video.


Next up you need to check the backlash. This will test the health of your shims and preloads on the bearings side bearings. Again you will need your dial gauge setup. Since there are many contact points, you will want to make multiple measurements around the gear. I made six and got the same measurement each time.

Clean the surface to be measured, and again set up the gauge and base so that it is as close to 90* of the part as possible. Also you need to make sure that the gauge is preloaded at least one revolution. The service limit for backlash is .004" - .006".

You must be logged in to view this image or video.


Now the manual says to lock the pinion in place. I did not find an efficient way to do this. What I did find is that you are measuring backlash. This is free play, so start by placing your thumbs 180* across from each other or 1 thumb 90* from the measurement surface on either side. Since the measurement is of free play, you can apply minimal force with your thumbs back and forth to get the measurement. If you rotate the pinion, you pushed too hard. This may take a few tries to get accustomed too, but you can do it. It would also help if you had a buddy to hold the pinion still while measuring. Again, the gauge does not have to be zero; you just need to know the difference between the extremes. For picture purposes, my gauge was zeroed and the reading is the actual backlash for that tooth.

You must be logged in to view this image or video.


The next test will consist of a little painting. This will check your pinion gear height and also double check your bearing preloads. You will need to get some gear marking compound. NAPA sells some Permatex Prussian blue marking compound, but it is a very dark blue making it hard to read. There is also a yellow compound. GM dealerships normally keep some 1 oz tubes on the shelf. The part number is 1052351 and runs about 12 bucks.

You must be logged in to view this image or video.


You will need some small paint brushes to apply the compound to the gear teeth. This set was 2 bucks.

You must be logged in to view this image or video.


Clean the teeth as much as possible. You may want to rotate it and clean them again. Just make sure that the surface you are painting is clean. Q tips are really nice at this point.

You must be logged in to view this image or video.


Use your disposable brush to apply the compound to the clean teeth. A little compound goes a long way. The manual says to paint all the teeth. I choose to paint a quarter or more just to do a test upon disassembly. If I were putting this back together, I would advise painting all the teeth to be certain the contact patch is acceptable.

You must be logged in to view this image or video.


After you have painted the gear teeth, you will need to get your contact patch. To do so, you will need to use a pry bar (or something similar) to load the gears. You only want to apply a slight amount of resistance; you do not want to hang off of the pry bar and try to turn the pinion.

You must be logged in to view this image or video.


While loading the gears with one hand, turn the pinion until the ring gear makes a full rotation. Now move the pry bar to the opposite side, load the gears, and turn the pinion one complete revolution in the opposite direction.

You must be logged in to view this image or video.


You must do a rotation in both directions to get a contact patch on the Convex (drive) side and the Concave (coast) side of the rear diff.

You must be logged in to view this image or video.


You must be logged in to view this image or video.


This contact pattern can tell you if you pinion gear is too high or too low, or if you have excessive or inadequate backlash. You want to see a contact pattern that is mostly centered, but refer to the FSM that you can download HERE ON TUNERS for the explanations of the contact patterns.

Now that those tests are done, we can take some things apart. First you will need to remove the 4 14mm bolts that hold down the bearing caps.

You must be logged in to view this image or video.


Once they are loosened, you can remove them just like cam caps. Pull the bolt up about half of its travel and squeeze them together with one hand now take a non metallic hammer and lightly tap each side 2-3 times. Then alternate. Rinse and repeat until the cap is loose and comes off. DO NOT PULL THE BOLT OUT SO FAR THAT YOU ARE PRYING AGAINST THE THREADS OF THE BOLT. This could cause damage to the threads and render the bolt useless.

You must be logged in to view this image or video.


Now with the caps removed, look for heat marks, pitting, or anything that look out of the ordinary. The dark black marks on the outer race wiped off with a rag and some elbow grease.

You must be logged in to view this image or video.


Now it is time to take out the LSD. The bearings are preloaded with shims, so this will take a little effort. The manual wants you to use two wedges, but this method ended in failure for me. I opted to use a BRASS punch and a non-metallic hammer. Notice the word BRASS!!!! The metal must be soft enough to prevent damage. I place the brass punch in the axle hole at an angle to catch the very beginning of the LSD. I then tapped the brass punch with a non metallic hammer 2-3 times. Then I alternated to the other side. I used this method to walk the LSD out of the Diff. When placing the BRASS punch inside the LSD, do not place it directly onto the splins. Instead catch the outer portion to avoid damage.

You must be logged in to view this image or video.


NOTE: Left side parts should be kept separate from right side parts. In other words, the shims are side dependent, and unless you are changing them they must be installed back into the same hole they came out of.

With the LSD loose, lift it out of the diff being careful not to drop the outer races or spacers. The easiest way for me was to stick my finger through the spacer, outer race, and bearing and then lifting it out.

You must be logged in to view this image or video.


Clean the races and bearings and again check for pitting, heat marks, and other abnormalities.

At this point, for LSD differentials, you are supposed to check the side gear backlash using a feeler gauge. They ask for a .0012 inch feeler gauge and a .0035 inch feeler gauge. The smallest feeler gauge that can be had locally is a .0015. This would have been fine as you just want to make sure the backlash is within tolerance, but the slot that you stick it in is about half the width of my finger???? This was so small that the feeler gauge would not fit width wise. I am sure there are feelers available that will fit, there was just nothing local on the weekend. It was also considered to just cut my feeler gauges to width, but this could effectively change their thickness making them useless. With that being said, I did not do this test and will not be further discussing it. If you would like to look into this, please refer to the FSM for further guidance.

With the LSD out, remove the 8 14mm bolts holding the ring gear on.

You must be logged in to view this image or video.


Tap down lightly on the ring gear in a circular motion using a non-metallic hammer. A few rotations and the gear will come right off.

You must be logged in to view this image or video.


With the ring gear off, you will be able to see two machine screws that hold the LSD cover on. Using your vice and some pieces of cardboard, clamp the LSD into the vise with the screws visible.

You must be logged in to view this image or video.


I had an impact driver that made easy work of these machine screws. Without this tool the chances of stripping these screws out will increase but it can be accomplished.

You must be logged in to view this image or video.
 
Last edited by a moderator:

BoostedBeaver

Moderator
950
252
Aug 15, 2009
Augusta, Georgia
Make mating marks on the cover and LSD case.

You must be logged in to view this image or video.


Then grab the cover bearing and pull up. The fluid has created suction and may make this somewhat challenging, but it will budge. Everything past this point should be kept in order!!!

You must be logged in to view this image or video.


You will be looking down at the viscous coupler and a thrust washer.

You must be logged in to view this image or video.


Remove the thrust washer and then pull the viscous unit out of the case.

You must be logged in to view this image or video.


Clean the viscous unit and check the teeth, axle splines, thrust washer surface and sides of the unit for signs of abnormal wear or discoloration.

You must be logged in to view this image or video.


You must be logged in to view this image or video.


You must be logged in to view this image or video.


You must be logged in to view this image or video.


Clean the cover and thrust washer while checking them for abnormal wear or discoloration.

You must be logged in to view this image or video.


You must be logged in to view this image or video.


Now you will see the cross shaft, differential pinion gears, and the thrust washers.

You must be logged in to view this image or video.


Slide this unit out carefully to keep the components in order.

You must be logged in to view this image or video.


Clean and inspect the gears, thrust washers, and cross shaft for abnormal wear or discoloration.

You must be logged in to view this image or video.


You must be logged in to view this image or video.


You must be logged in to view this image or video.


The last thing to pull out is the side gear. This will also have a thrust washer under it and will more than likely be suctioned to one side or the other. If you have a difficult time removing it, use the access holes on the side of the case to get it started.

You must be logged in to view this image or video.


You must be logged in to view this image or video.


Again, clean and inspect the teeth and thrust surfaces for abnormal wear or discoloration.

You must be logged in to view this image or video.


Now you should inspect the wear surfaces inside the case. In particular you should check the 6 thrust washer surfaces, the cross shaft slots, and the viscous unit walls. There is a great diagram in the FSM for these points.

You must be logged in to view this image or video.


You must be logged in to view this image or video.
 
Last edited by a moderator:

BoostedBeaver

Moderator
950
252
Aug 15, 2009
Augusta, Georgia
My work bench now looked something like this.

You must be logged in to view this image or video.


The last portion to test and remove is the pinion gear.

To test the pinion gear preload, you need an inch lb torque wrench (needle or dial type, not the clicker or digital type) and a 27mm or 1 1/16 socket.

You must be logged in to view this image or video.


What you want to check is the rotational force. Extensions are discouraged, but I did not have a 1 1/16 socket in a 3/8 drive. Place the socket and torque wrench on the nut. Turn the pinion using the wrench and read how many inch lbs of resistance you have.

You must be logged in to view this image or video.


Unfortunately, my inch lb wrench is graduated in 5 inch lbs so I was only able to get a good approximation of 6 in lbs. For specifications, refer to the FSM. I say this because there are specs with the oil seal, without the oil seal, with lube, and without lube.

After this final test is complete, make matting marks on the pinion flange and threads of the pinion gear. Use that same socket and an impact to remove the nut. You also use a pry bar and two bolts to hold the pinion while you removed the nut and washer.

You must be logged in to view this image or video.


Simply pull up on the flange to remove it.

You must be logged in to view this image or video.


Inspect the splins of the flange and pinion gear shaft.

You must be logged in to view this image or video.


Next take a non metallic hammer and press the pinion gear through the case. Once the shaft has broken loose and started to move, tilt the diff and hold the gear with one hand while finishing the job with the other.

You must be logged in to view this image or video.


You must be logged in to view this image or video.


Once the shaft is out, you can remove the spacer shim and spacer from the pinion shaft.

You must be logged in to view this image or video.


You will now notice that there is an oil seal holding in a bearing. You will need to pull the oil seal out in order to retrieve the bearing. I found no way possible to preserve the seal so destruction was a must upon removal.

You must be logged in to view this image or video.


With the seal removed, retrieve your bearing.

You must be logged in to view this image or video.


Clean all of the pinion gear parts and check them for abnormal wear or discoloration. Also check the condition of the pinion gear itself.

There are two things that I did not cover and those are removing the LSD bearings and removing the pinion shaft out races. The LSD bearings will need to be pressed off, and the pinion shaft outer races will need to be pulled out using a slide hammer and a bearing puller both rentable from AutoZone. While the bearing puller there does work, I purchase a miller tool for 12 bucks when re-doing the tranny and it works much better. The part number is Miller 9664. I will get this number when I get home.

Another thing to note is that the pinion nut is not reusable. It is a convex lock nut and should be replaced when being removed.

At this point you should have a good idea of the health of your rear and hopefully find the problem you where looking for. In my case, everything looks fine and I cannot find anything that is making my growling noise. HHMMMMMM...

Stay tuned and please use the RATE THREAD button!!!!! Any and all suggestions/comments/ constructive criticism is welcome.

Robert
 

Attachments

  • IMG_2833.jpg
    IMG_2833.jpg
    167.3 KB · Views: 19
Last edited by a moderator:
Support Vendors who Support the DSM Community
Boosted Fabrication ECM Tuning ExtremePSI Fuel Injector Clinic Jacks Transmissions JNZ Tuning Kiggly Racing Morrison Fabrications MyMitsubishiStore.com RixRacing RockAuto RTM Racing STM Tuned

Latest posts

Build Thread Updates

Vendor Updates

Latest Classifieds

Top