|1990-1996 U.S. Z32 300ZX Urethane Differential Bushing Replacement
Write-up by Mike Smith, Jan 15th, 2003 all rights reserved. Use this information at your own risk, there is no guarantee that any or all steps have been included, nor that any have been excluded. There are no guarantees that damage will not occur to your vehicle due to anything included/excluded in this write-up, poor quality tools, poor lighting, lack of mechanical ability, or any other unforeseen, unaccounted for, or uncontrollable factors. This information may be copied, in whole or in part, to be distributed for personal use only. Please include all rights and disclaimers if this information is copied. That said, let’s get on with it.
This job went pretty smoothly, but took quite a while and you need to have the right tools on-hand or you could be there for a while. The factory differential bushings on my 1991 NA 5spd with 170,000 miles on it had seen much better days, and my differential would "clunk" loudly whenever you got on or off the gas...really annoying, especially in traffic. Plan on the job taking at least a couple hours, if everything goes smoothly, I would say it took us about 5 or 6 hours over 2 days. I have heard other people mention needing presses to press out the bushings, or having to burn them out, etc. I did not have to do anything near that destructive nor labor intensive as removing the subframe....the tools I used were:
1/2" drive socket set
box/open end wrench (14 mm??)
drill and bits
heavy hammer =)
1/2" X 8” bolt
various washers and spacers
First chock front wheels, apply handbrake, jack up car, put on jack stands.(Please be careful here guys, you need to do some cranking on stuff pretty good, and will have to be mostly under the car to move the differential and all, so chock the wheels really well so the car can't roll forward.)
Unbolt and remove the two mufflers.
Remove the hangers from the back end of the "X" or "H" pipe. I have a GReddy PE and could leave it’s H-pipe attached to the cats and just had someone push down on the rear ends a little to give me the clearance I needed to unbolt the front differential support(mustache bar).
At the rear of the car looking forward you will see two small(10mm?) bolt heads, one on either side of the rear differential mounts towards the top of the subframe. Remove these and the brackets that they attach to the subframe, and undo the connector. These go to the ABS sensors on the half shafts on the differential.
Put floor jack(using pieces of wood as needed) under differential and lift it slightly to take the weight off the mounts.
MARK THE FLANGES ON THE DRIVESHAFT AND ON THE DIFFERENTIAL SO YOU CAN PUT THEM BACK TOGETHER IN EXACTLY THE SAME ORIENTATION SO YOU DON'T GET THE DRIVETRAIN OUT OF BALANCE.
Undo the 4 nuts(14mm?) holding the driveshaft to the differential. There were 4 bolts on my NA, but I think TTs may have 6.
Undo the 4 bolts(17mm?) that hold the support under the front of the differential(mustache bar) to the subframe. This is where your "X" or "H" pipe may or may not be in the way too much if you have left it attached to the catalytic converters.
Front Bushings Removal:
Now comes removing the front bushings from the differential. I am not really sure how they are supposed to look as mine literally fell out of the differential when I removed the lower support bolts. The little metal sleeve in the center of the bushings had broken free and worn most of the rubber off the inside of the metal sleeve that makes up the outside of the bushing.
The bushings are supposed to be one-piece. That is, there is a center metal sleeve that is bonded to some rubber which in turn is bonded to an outer metal sleeve that is a press fit into the front “ears” of the differential. I used a socket that was just smaller in OD that the outer metal sleeve of the bushing was attached to an extension as a driver and used a hammer to knock them(the outer metal sleeves) out of the differential(out of the front “ears”). They come out from the bottom up and mine came out nice and straight, and didn't get sideways or anything. Not too difficult to do at all. In the first picture below, you can see the sleeve being hammer out with the socket. It has a flange on the top side of the differential “ear”, you can see the flange is about ¼” clear of the “ear” in the picture. The second picture shows the front ears of the differential from below. On the left side of the picture you can see that the sleeve has been knocked out, on the other side it is still in place. The third picture shows my bushings and sleeves after they were removed. You can see how badly deteriorated they were.
Picture 1: Using a socket and extension to knock the outer sleeve out of the differential.
Picture 2: On the left the outer sleeve is removed, it is still installed on the right side.
Picture 3: A picture of my old bushings and sleeves as they looked once they were removed.
MARK THE FLANGES ON THE HALFSHAFTS AND ON THE DIFFERENTIAL SO YOU CAN PUT THEM BACK TOGETHER IN EXACTLY THE SAME ORIENTATION SO YOU DON'T GET THE DRIVETRAIN OUT OF BALANCE.
Undo the 5 nuts(14mm?) holding each half shaft to the differential flange using a wrench. The clearance is too close to get a ratchet on, and the wrench alone will not give you enough leverage, so you have to use another, larger wrench on the end of the 14mm to get enough of a lever arm to break them free. Even then they are still on tight, it helps to have someone pushing and someone pulling if you have the luxury of a helper. It is also useful to have a helper to put on the handbrake for you when you are under the car, and release it so you can rotate the shaft to the next bolt. The brake has to be on for you to break the nuts free, but you can only get to two nuts at a time, and have to keep releasing the brake and turning the axles to get to the next 2 nuts. The shafts should fall away easily once unbolted. They are sealed, no oil or grease will come out when the half shafts come away from the differential.
Undo the two nuts holding the differential in thru the bushings in the rear subframe. These nuts attach to studs that are part of the differential housing and the studs pass through the rear differential bushings.
The differential should now be totally free and supported only by the jack. You can get it out without removing the anti-sway bar. In fact I found it useful to leave the anti-sway bar installed and use it as a place to hang the front of the differential when try to get it back into the rear bushings on re-installation. You will need to move the differential forward to get the studs to clear the rear subframe bushings so you can lower the differential out of the car. Gently lower the differential using your floor jack and pull it out from under the car. See pictures 4 and 5.
Picture 4: The differential removed from the car.
Picture 5: Here is what your car will look like with the differential removed.
Sit back, relax....go grab a cold beer and admire your differential sitting there on the jack :)
OEM Bushing Removal:
Next turn your attention to the larger bushings in the rear subframe. These bushings are similar to the front bushings in that they should be one-piece. There is a central metal “cup” that is bonded to rubber which is in turn bonded to another metal out sleeve that is a press fit into the subframe. On my car, one of the little metal "cups" at the center of the bushing was only held on by two tiny places where the rubber was left intact and twisted out easily using my puller bolt passed the hole to twist the inner cup(see pictures 6 and 7). On the other side, I used a drill to drill thru the rubber between the inner cup and the outer sleeve in several places using about a 1/8” bit. Then, insert the 1/2" bolt that you will use as your puller later, and use it to wrench and twist the inner cup free. Don't damage the inner cup as you will need to re-use it later.
Picture 6: A look at the old rear bushings. You can see how my left side bushing was completely shot.
Picture 7: This is a close-up of the right side bushing that was not destroyed. Notice the thick walled inner metal cup, this is the part you want to save. Outside of that is the rubber section(a little thicker than the inner cup wall) that you want to run your drill through to separate the center section. You can see the distinct outer “lip” of the outer bushings shell also. It is the thinner, third ring out from the center. The large, rounded over outer circle is the actual subframe. Don’t damage it!
To remove the outer metal sleeve and residual rubber, I used a chisel to curl in the lip of the outer metal sleeve of the bushing and knock it thru. I held the chisel so that the blade ran vertically and placed it on the lower edge of the metal sleeve so that it met the sleeve at 90 degrees. As you hammer on the chisel, you will start to curl the metal sleeve in on itself towards the center of the bushing. Once you get it folded in on itself enough, the sleeve will knock right out of the subframe without damaging anything. It feels like it is in there really good when you first start hammering on it, and it will make a very unnerving solid sounding “chunk, chunk” as you first start hammering on it. That is OK, keep going :) See picture 8.
Picture 8: Using a chisel to knock out the outer sleeve of the OEM bushing.
Take the little metal cups that were in the center of the rear bushings and clean them up, paying careful attention to remove all the residual rubber on the outside of them. I used a propane torch to char the rubber and it crumbled right off, then used a wire wheel to clean off the rest. Something to note here, DO NOT get the cup too hot with the torch or the metal will loser its heat treatment. You only need to char a bit of the rubber at a time and it will come right off using a utility knife , wire brush, or similar tool.
Picture 9: One of the metal “cups” you need to save, with the OEM rubber still bonded to it. This was the left side on mine that was already ripped apart on the car.
That's it for removal........clean up your differential now if you like. I thought the ABS sensors were optical for some reason and was worried about getting crap on the sensor when cleaning it. Anyway later when I thought about it I figured the sensors were probably Hall effect sensors or some other type of magnetic sensor that is not affected by crap getting on it, after all it's environment is under a car. Point is, feel free to degrease it without worry of damaging it. Someone correct me if that is wrong, please.
Energy Suspension Urethane Bushing Installation:
The front bushings are dead easy to put in. The go in with the "mushroom" head on the top and just press into the differential “ears” using a piece of wood to tap them in. Just to reiterate it, they fit into the differential so they look like a mushroom growing out of the ground, stem pointing down and cap on top. Next put the new metal sleeve(supplied with kit) thru bushing and slide the large flat urethane washer on the bottom. Do not try to put the sleeve into the bushing first and then try to hammer it in, as you will find it most difficult. When you push the center sleeve through the bushing it expands it.
Picture 10: The urethane front bushings installed. The flat urethane washers are on the underside of the “ears” and not visible from this angle.
The rear bushings are not quite so easy, however. The method I used was to rig up a puller to pull the bushings into the subframe. I found on my coupe(2+0) there was not enough room between the subframe and the gas tank to get a decent swing with a hammer. A 2+2 might be different, but by the bushings very nature, they absorb the blow rather than get moved by it anyway. The bushings are inserted from the rear, and the chamfered outer edge is the one that goes in first. The inside tapered end is supposed to face the rear so it will be easier to insert the metal cup into it. I used a 1/2" X 8" bolt and some galvanized pipe pieces and washers from the hardware store. Make sure to get some BIG washers(like 3" or 4" if possible) that are bigger in diameter than the bushings outer diameter. Put something that is larger than the hole in the subframe on the front side of it(I used a rusty pulley I found in the shed in the pictures, lol). Slide the washers and spacers over the bolt to get the spacing right so you can tighten the nut and draw the bushing into the subframe without running out of threads too fast on the bolt, and slide the bolt from the front to the rear thru the bushing. Put a big washer or two over the bushing and put the nut on the end. As you tighten the nut, the bushing will be pulled into the subframe. Once it is most of the way through, you will not be able to use your puller setup anymore, unless your spacer on the front side of the subframe has a larger inner diameter than the outer diameter of the bushing. Basically the bushing bottomed out on my pulley I was using on the front side of the subframe, and I had to figure out a way to get the bushing the last 3/8”-1/2” through the subframe so it would “pop” though. In hindsight, a piece of pipe on the front side of the subframe that had a larger ID(inner diameter) than the OD(outer diameter) of the bushing would have let you pull it all the way into place through the subframe. I ended up using the puller assembly as a lever to push and pull the bushing, and it popped thru on the forward face without too much drama.
Picture 11: The puller setup I used to “draw” the rear bushings into the subframe. Left is forward in this picture.
Roll the differential back under the car and lift it using your jack. Lift the front of the differential, the driveshaft flange, over the anti-sway bar and push the whole differential forward. This should give you enough room to rotate the back end up and align the studs on the differential with the holes in the rear bushings(Don't put the little cups back in yet....) Move the differential as far back into the rear bushings as you can now. Move the differential by lifting it on the floor jack and moving it side to side by hand until you get the studs pretty much centered in the bushings. Tap the metal cups over the studs. The inside of the cup should face you(face the rear of the car) as you are tapping it on. Once it is on far enough, start the nuts on each stud. Leaving things loose, turn your attention to the front of the differential. I had to remove the floor jack to get enough room to slide the front differential support into place, but you may not have to. Move the differential slightly as needed to get the 4 bolts started, no alignment problems at all here! Loosely tighten all 4 bolts and 2 nuts holding differential into place.
Find your alignment marks on your half shaft flanges and driveshaft flanges, and reinstall driveshaft and half shaft fasteners. This will require putting the handbrake on and off and tightening 2 bolts at a time just like in the removal sequence.
Reinstall ABS brackets and mounting bolts, and reconnect the connector.
Tighten the 4 bolts and 2 nuts holding the differential into place.
Picture 12: This shows the urethane bushings and the differential installed.
Picture 13: Close-up of the rear bushings installed. Note the ABS sensor brackets and mounting screws near the top of each bushing.
Reinstall exhaust system hangers.
Reinstall you mufflers.
Lower car, remove jack, sit back, and let out a big, contented sigh =)
Congratulations, you’ve just finished your differential bushing replacement.