By Brian Ruiz
Do you feel a "clunk" when you let out the clutch? Or does your car jump and/or clunk when changing into drive from reverse or reverse from drive on your auto tranny? Well, it's guibo changin time!
Following is the detailed recounting of my own experience changing the guibo (or more commonly known as the flex-disc) and center support bearing (CSB) on my '84 318iA. I claim no responsibility for a difference in procedures necessary to complete the project on other models, although the procedure will be relatively the same on all '84/'85 318i models - whether automatic or manual - and other E30s. I also claim no responsibility to injuries incurred while carrying out the following procedures. Although I will try my best to warn you of unforeseen potentials for injury, I cannot list every possibility. I recommend printing this out and taking it with you to your chosen location to carry out the occult procedures that follow. You may want to read through the procedure that follows before dedicating yourself to the job, as well as to become familiar with the intricacy of the tools and labor necessary to do a thorough and complete job. Otherwise, bring the car to your trusted mechanic.
Sorry for the lack of pictures;
I only realized I could have taken them after I reinstalled the driveshaft.
Materials Needed
2) Chock both forward and behind your front wheels, or if not enough chocks are available, the front of one wheel and the rear of the other. Be conscious of the possibilities of injury while under your car and take measures to prevent them. (I can just see the headline now: "Man dies while attempting to replace rubber under his car.") Begin by removing the exhaust system. Work from the back to the front when removing exhaust components; believe me it's easier. Also, be patient; they can be very rusty and worn and you'll certainly regret your impatience when you need to have a new flange welded on or a bolt drilled out. On stubborn rusted nuts/bolts, don't forget your WD-40. There are (4) 14mm nuts holding the exhaust pipe to the exhaust manifold, and (3) 13mm nuts holding the cat. flange to the downpiping. Remove other screws/bolts/nuts that you may have holding your exhaust to the frame. Once it is all out, be sure to put it in a safe place where it won't fall and where nothing will fall on it. Remove the four 10mm bolts holding on the rear heat shield (directly in front of the differential). Then remove the (6) 13mm bolts securing the aluminum heat shield above where the catalytic converter and downpiping were. You will also need to remove the (6) bolts securing the crossmember just rear of your transmission to fully remove the heat shield without damage. AAAH, there is the driveshaft in all it's glory!! Pause a moment if you wish to allow your elbows to relax...aaah doesn't that feel good? Using this time, you may want to inspect other areas under your car: metal fuel and brake lines, short sections of rubber fuel hoses near the fuel pump forward of the rear wheel, and rust beginning to form in areas where the undercoating has been worn through or deteriorated due to prolonged oil saturation. Take charge of the commonly ignored undercarriage health of your vehicle. :)
3) Using a small pipe wrench or large channel-lock pliers, loosen several turns but DO NOT remove the coupling securing the two sections of the driveshaft together, just rear of the CSB. Mine was particularly difficult to loosen; I insisted I could remove the driveshaft without removing the cat. converter (my downpipe and muffler were already removed due to other problems), so I had limited space to loosen; I soon gave up and removed the rest of the exhaust, realizing the CSB would not fit between the cat. and the underbody.
4) Assuming you took my advice and sprayed the guibo and differential nuts & bolts the day before you disassemble everything, get out your 17mm combination wrench, and with your car left in gear with the parking brake on tight (if a manual, or in neutral with an automatic...of course this is with the rear end on jack stands - if you can fit under the car with all wheels on the ground and have enough elbow room, this is better), loosen the nuts on the transmission output flange and on the rear driveshaft U-joint to differential input flange. This may take a while, so be patient and keep a good watch on everything. If possible in your situation, to loosen the guibo mounting nuts and bolts, you can place a large hose clamp around the guibo and tighten it slightly to aid in the removal AND later installation of the nuts and bolts. I don't have a hose clamp that huge (don't know many people that would) so I personally did without this - after a minor amount of fussing I was able to remove all of the bolts from the guibo.
TIP: If the guibo bolts are particularly stubborn, and if the car is on jack stands or on very level ground, when trying to loosen some of the more stubborn ones, put the tranny in neutral and take off the parking brake. Put your socket (17mm) on the bolt head, and use a combination wrench to loosen the nut. Turn the driveshaft slightly by hand until the handle of the ratchet locks up against the edge of the tranny hump (you might not understand what I'm saying, but you will when you see everything under the car). Make sure that the socket has a good grip on the bolt head, or as soon as you start torquing the nut off, the ratchet may slip off, hitting your precious noggin (ask me how I know).
5) Paint an alignment mark across one of the flange arms on the rear driveshaft U-joint to differential input flange. Once you have removed the guibo nuts/bolts and the rear driveshaft U-joint to differential input flange nuts, loosen the 13mm bolts holding the CSB to the underbody. BE SURE to support the weight of the driveshaft with blocks or with your body (don't worry it's not very heavy) once the CSB bolts are out. Bend the driveshaft down at the CSB, slide towards the rear, and pull the front section off of the centering pin on the transmission output flange, then off of the differential input flange. Be extremely careful not to drop or dent the driveshaft; doing so results in an unbalanced driveshaft, and causes BAD vibrations if it is reused; this will necessitate driveshaft replacement - an expensive part to say the least, not to mention transmission or differential damage that may be incurred due to high and prolonged vibration if you use a dented driveshaft. Remove the old guibo and discard.
Just a little note: You may find it easier to lay the driveshaft down closer to one side of the car, then get out from under the car and pick up the driveshaft from there, rather than trying to lay it down all the way out from under the car.
6) Being the clean freak that I am, I opted to spray down the easily accessible sections of the driveshaft with degreaser, then to rinse after letting it soak in for a bit. It does dull the driveshaft finish, but if there's as much oil leaking onto your undercarriage as there is on mine, you'll replace that dulled finish with nice gleaming oil by the time you're done handling it.
7) By now, you should have taken the guibo completely off of the driveshaft and transmission output flange; if not, go ahead and try to finish taking them off, but you might need an assistant to hold the driveshaft while you try to loosen the tight bolts.
NOTE: if you are planning to replace the transmission output shaft oil seal as well, now is the time to do it.
8) Before disassembling the two sections of the driveshaft, mark their alignment with paint or gold/silver marking pen ALL THE WAY across the coupling sleeve to the threads on the other end (the coupling sleeve turns, so only marking to that will not show the proper alignment). Loosen the coupling sleeve completely and pull apart the two sections of the driveshaft. You may wish to clean the splined ends of the two sections with degreaser before reassembly to eliminate wear due to excessive dirt. Let them dry thoroughly.
9) Use a pair of C-ring pliers to remove the snap ring on the outer end of the driveshaft. Once it is off, remove the metal dust cap. If you don't have C-ring pliers, you can also use a pair of regular needle-nose pliers to pull the ring off, after lifting it up with the edge of a screwdriver. If your new center support bearing comes with the rubber mount (mine did), the removal of the old bearing is aided by cutting off the rubber part of the mount with scissors (the arms of my puller didn't fit around the mount AND bearing). Since mine was fairly well worn and cracked, cutting was extremely easy. Take note of the orientation of the CSB on the shaft before removing it. Using a puller, pull off the old rubber bearing surround, being careful not to pull on the integral dust cap too; the bearing surround is very narrow, and very close to the dust cap. If you don't have a puller, borrow one. If you can't get one, you can remove the bearing after removing the rubber bearing surround using a large picklefork and hammer, or if that's not available, a large flat-ended nail punch and hammer. Pound with the nail punch on opposite sides of the outer race of the bearing to slowly slide it off the shaft.
10) Once the bearing is removed, clean off the shaft where it was mounted. Put a light coat of grease on the shaft to assist bearing installation, and if you didn't take note of the bearing orientation prior to removal, the side of the mount with the wider opening goes down (facing the dust guard). Press the new bearing down onto the shaft by your desired method, taking care not to smash your fingers if pounding methods are employed. I placed the inner race of an old wheel bearing around the shaft, and pounded on it using a flat-ended nail punch and hammer. Be VERY careful not to damage the bearing, the bearing seal, or to gouge the shaft. Take the dust cap you removed previously and clean any loose grit, oil, grease, or other debris from it using a good degreaser. You want to reduce the possibility of premature failure of your bearing because of dirt contamination. My manual says the rubber bearing surround should be flush with the integral dust guard on the driveshaft. Once you finish placing the bearing on the shaft, place the clean dust cap on top and try to replace the C-ring. If it is too tight, don't bother forcing it. The dust cap and C-ring must NOT be tight against the CSB. Give the dust cap a few good turns to be sure that the cap isn't rubbing too tightly. If it is rubbing, you'll have to push the bearing a little further down on the shaft, taking care not to push it so far that the U-joint begins to rub on the rubber bearing surround instead. The cap should be loose enough to either turn along with the driveshaft without too much friction on the CSB, or to stay in place against the CSB. If the dust cap is too tight, it will turn with the driveshaft and begin to melt the rubber mount around the CSB. (As if you need to ask me how I know).
11) Get out your new guibo and mount it to the three-armed end of the driveshaft. Use three of your new locknuts. The arrows MUST POINT TOWARDS THE FLANGE ARMS, NOT TOWARDS THE BOLT HEADS!! Tighten the nuts and bolts to 34 ft-lbs if they are (M10) grade 8.8 bolts, 53 ft-lbs if they are (M10) grade 10.9 bolts, and 90-91 ft-lbs if they are M12 bolts.
12) Lube up the splines of the two driveshaft sections with moly-based grease. Align the marks you made before disassembly, and slide the splined section of the driveshaft into the other section. Tighten the coupling sleeve just enough to prevent the driveshaft section from falling off - DO NOT tighten completely. You will need to loosen the coupling once you remount it on the car if the driveshaft doesn't reach the transmission output flange or differential input flange. If you only now realize that you didn't mark the two driveshaft sections correctly, then position the two sections so that the U-joints are in the same plane. If, once you have reassembled and reinstalled the driveshaft, you experience abnormal vibrations, the U-joints are 180 degrees out of balance. Repair will necessitate the removal and separation of the two sections of the driveshaft, rotating one section 180 degrees, and reinstalling - in other words, take care not to align the two sections improperly. If in doubt, ask your mechanic or gearhead friend.
13) Once you have the guibo mounted on the driveshaft, the splines lubed, and both driveshaft sections reassembled, apply a light coat of moly-based grease to the centering pin on the transmission output flange. Time to get under the car again! Place the driveshaft within comfortable reaching distance from under the car, and slide on under your baby.
14) Position the driveshaft against the differential input flange first, slide it onto the centering pin on the transmission output flange, then push up the driveshaft at the CSB and loosely install the mounting bolts, but don't tighten them yet. Make sure you align the mark you made on the rear driveshaft U-joint with the mark on the differential input flange. If the driveshaft doesn't reach the tranny output flange once it is on the differential input flange, loosen the coupling sleeve off of the threads on the front section of the driveshaft, and pull it until it will reach the centering pin on the transmission. Ensure that the arrows on the guibo are pointing towards the driveshaft flange arms, then use (4) of your new locknuts and place them on the studs going through the differential input flange. Don't tighten them yet. Take the other three guibo mounting bolts and place them the same direction (the only way they'll go on my car) through the three remaining mounting holes in the guibo through the holes on the transmission output flange. Tighten the nuts to 34 ft-lbs if they are (M10) grade 8.8 bolts, 53 ft-lbs if they are (M10) grade 10.9 bolts, and 90-91 ft-lbs if they are M12 bolts. Again, a hose clamp can aid in the installation of the bolts, but I didn't use one. I only needed a very minor amount of fussing to get the bolts through. Go to the rear of the car, and using a 17mm crow's foot, if you have them, tighten the nuts to 53 ft-lbs. I couldn't get my crow's feet to properly tighten the nuts, so I just tightened them by hand with my trusty combination wrench.
15) Get back under the car where you can fuss with the CSB comfortably. My manual says to "preload the center bearing by pushing it forward 5/32"-15/64" from it's unloaded position and tighten the bolts to the torque listed in this Chapter's Specifications." I have NO idea of the use of doing this, and I wasn't about to sit under the car and measure 5/32"-15/64" forward of the CSBs unloaded position, so I just pushed it forward a tad and tightened the bolts to 16 ft-lbs. I hope it doesn't hurt anything. :-O
16) You can now retighten the coupling sleeve to 13 ft-lbs (if possible), but otherwise just tighten it to what you think is 13 ft-lbs. Make sure all the bolts on the guibo and driveshaft input flange are tight and flush before tightening the sleeve, however.
17) The remainder of installation is basically the reverse of removal. I torqued the nuts on the exhaust manifold to pipe connection to 15 ft-lbs. I figured it'd be enough, but I'd recheck after they heat up and cool down again.
18) In case you have forgotten, the (6) bolts with the cutouts on the end (self-tapping) go on the heat shield that goes above the cat. and downpiping. The (6) regular (and longer) bolts go through the crossmember and into the underbody.
RESULT: A replacement guibo and CSB will help your car feel A LOT tighter, especially if the old ones were in bad condition.
Revised: 3.5.2001 7:32:33
