GTV6-Milano Driveshaft Repair

Tech Session Notes

by Roger Medlin

Peter Krause held an excellent tech session for nine very interested Alfisti on the subject of driveshafts--items unique to Alfas in their design with the cast rubber doughnut couplings known as "Guibos." Peter started with the six cylinder models which are quite similar to the Alfetta and the Sport Sedan drive trains. The first usage of the De Dion suspension in Alfas was in the 8C 2900 and the tipo 159 race car, per Luigi Fusi. The De Dion axle arrangement dates back to the 1890's, where it was used in cars to reduce unsprung weight. and to keep the driving wheels parallel with constant camber (usually zero) to keep them perpendicular to the road. The concept was patented in 1894 by Albert, Comte de Dion and Georges Bouton. Because of the geometry of the system, the flex-joints are required. Only some high performance cars used the De Dion arrangement, due to the high cost of the design.

The driveshaft is divided into two sections. coupled with a guibo in the center of the design, bolting both halves together. This is mounted behind the center support at the rear end of the front driveshaht section. At each end of the assembly there are guibos connecting to the driveshaft-to-clutch yoke in the rear and to the flywheel-to-front coupling at the cngine.

The guibos are the usual items to fail. They are constantly stressed to transmit engine torque to the clutch flywheel in the rear mounted clutch/transmission/differential assembly. The guibos absorb rotational shock and allow the flexing of the driveshaft in other planes. They are made of cast rubber with inserts for the connecting bolts. The guibos have casting marks showing the date of manufacture and usually fail by loosing a chunk of rubber from between the mounting bolts, due to stress cracks developing over time. You can reasonably expect to have to replace guibos every three to five years. The failure is accelerated by usage and age. We all know that rubber hardens and looses resilency with time, and it certainly has been true of Italian rubber. You should be able to inspect your couplings and note cracks. and certainly broken sections. The problems are usually evident from driveability clues, such as vibrations at different speeds. A very serious problem associated with partially broken guibos is accelerated wear of the nose ends of the driveshaft, causing support bearing wear and possible distortion of the bearing shaft end in the driveshaft nose or the end where the support bearings are. This wear can cause vibrations at certain speeds due to either (or both) worn bearing races or a bent end of the shaft. This causes an elliptical or off-center rotation, "whipping up" vibrations.

The best way to replace driveshaft guibos is to remove the entire driveshaft assembly and do the work "out of the car". This also allows easy checking of the bearings at each end for wear and inspecting the center support bearing assembly. It is most important to mark the center guibo mountings so you can maintain the same relationship between the two driveshaft sections. Marking the front and rear guibos is not critical, since they are connected to the engine and clutch couplings, not to the other driveshaft. Removal of the driveshaft assembly is not easy, but with care it is within the home mechanic's scope. The best way to do the job is to remove the rear muffler section the heat shield, unbolt the shift linkage rod from the bottom of the gearshift lever, and remove the cross member from under the driveline. Loosen the nuts at the rear and forward guibos. It helps to have someone depress the brakes or put the car in a high gear to keep the driveshaft from turning.

Loosen the center support bearing bolts noting that the assembly goes in with the long side to the driver. The bolts are of different lengths at the different guibos, keep them straight. Now by jacking up the De Dion tube, the assembly is tilted forward and after finishing the guibo bolt removal you can slide the drivshaft assembly forward down and back for removal.

The center guibo. which vou have marked for proper realignment. may be unbolted so the front shaft propeller assembly can be taken off to get to the center support. The yoke is held by two thin nuts which are very vulnerable to damage, so be very careful not to burror damage the threads. Now the center support can be removed and inspected. The usual wear mode is not breaking of the rubber insert holding the bearing assembly but a sagging down so the bearing is not centered in the support. (A good time to probably replace it if the sag is evident).

The Milano and the GTV-6 use the same front and rear guibos, but different center ones. The guibos come with a band around the perimeter which allows for the bolt installation, and shouldn't be removed until the final steps, after the bolts are secured.

Speaking of the guibo bolt and nut assemblies, Fred Di Matteo has written that he has seen different thickness washers and doubled up washers used in guibo assembly, for balancing purposes. Peter said that he has never run into this, so be aware of the possibility and note so if found. There is normally one washer per bolt under the nut. Keep the nuts and bolts together because of their different lengths front and rear. Note that the old guibos have dust shields to keep dirt and moisture out. Replace the seals for proper wear protection. New guibos do not come with seals, use the old ones or order new ones if necessary. After Checking for wear on the components and replacing any worn bearings, etc. its time for reassembly. When reinstalling the driveshaft assembly, don't bolt everything up tight at first. This allows for alignment of the bearing sleeves and center support, and checking for proper free play. Do not forget to lubricate the driveshaft bearings and sleeves on reassembly. Pay particular attention to the splined shaft at the engine end, it only goes together in one way due to a flat key, but it must be lubed. When you are certain components are aligned and properly placed, bolt everything up according to specs and be sure you removed the guibo metal assembly bands.

We then spent some time on discussions the four cylinder Spider driveshaft, which is less complex but does have two universal joints that bear inspection. The universal joints have springs in the cross hub which runs in the needle bearing. On disassemble check out the spring locations and put them back there in the new universal joint assembly. The cntical thing is to be sure the two springs are ninety degrees apart to dampen vibration in both axes. In removal of the drivshaft, you can unbolt the gearshift under the car after removing the boot. This is better than having to realign the console which you must do if you work from the top.

Be sure you are ready for the job if you plan to do it yourself. A competent Alfa mechanic will require five to seven hours to do a driveshaft rebuild and replacement. Also be aware that no Alfa manual gives instructions for this job. I have found that decent instructions are included in the Haynes manual "Alfa Romeo Sedan & Coupe 1973-1980," chapter five. Be aware, however that the six cylinder cars are different. For the four Cylinder Spiders you can refer to Autobooks "Giulia 1750 2000 Owners Workshop Manual". The Autobook manual Cover cars from 1962-1976 but it is basically good for all Spiders.

Special thanks to Peter Krause for a great tech session, he has reviewed this for big errors, so it should be correct.

Milano-GTV6 Front Donut R&R

from Velocissima, Alfa Owners of New England, 1993

By Fred Di Matteo

Due to the number of requests for information about "how to" replace the front flexjoints the easiest way, I decided to do this article because, quite often over the phone some details are omitted or forgotten and it can become a bear of a job. If you don't have a lift you'll have to raise the whole car at least 18 inches!

Most Milanos have a drive shaft that does not have a splined coupling at the front end, I know of at least one that does however. The GTV-6s do. In either case, there is an easy way, after the exhaust system is removed.

If the last time the exhaust system was renewed or replaced, and no anti-seize was smeared on joints and bolts, you may very well be facing a rather sticky job. Applying plenty of penetrating oil over a period of a few days to joints and fasteners might loosen things a bit. If not, try local heat with a torch. Need I stress the danger and the need for plenty of fire prevention?

Remove the rear resonator and try to be careful and not tear the half-shaft boot. Remove the catalytic converter right up to the flange connecting to the manifold. I hope the nuts come off without breaking the studs, they tend to rust badly and errode enough to make them weak. Having spares on hand is wise.

If you're successful and don't break any studs, drop the pipes as far as you can and then tape or were the spacers up in place to keep them away from the pipe ends. Once that is done, being very careful not to damage the studs, twist and turn the pipes gently to find the combination to its removal. Brute force is NOT THE WAY!

Next remove the heat shield from above the converter and the gear shifting rod. Remove the 3 nuts holding the donut to the flywheel. Go to the rear flexjoint and remove the 3 bolts that connect the donut to the crow's foot (input shaft). Next remove the 2 bolts that hold the bell housing rear motor support. (the bar that goes through the round rubber busing). Go to the center support and remove 4 bolts that hold the cross-member amd remove.

Now remove the 2 nuts that hold the center bearing in place. Don't lose any spacers up there. Notice the shaft drops down a bit and vou can see it come away from the rear input shaft crow's foot. you are effectively shortening the shaft and when it clears the crow's foot, pry the rear motor support down enough to withdraw the front donut. If your car has the splined section mark the alignment before separation, loosen the adjusting bolt, spray the spline with WD40 or similar or withdraw and then separate.It's best to use a vise to hold the shaft while changing the flexjoint. DO NOT REMOVE THE METAL BAND until after it is put back in the car. DON'T FORGET TO CUT IT LOOSE AFTERWARDS!

For GTV6s and cars with the spline, leave the spline loose until you have let the engine idle through a few revolutions which will self adjust to the proper driveshaft length. Don't forget to tighten and use plenty of anti-seez. Before installing the shaft, grease both ends and keep it clean! Everything goes back in reverse order. Good luck!

If you ever have to separate the two halves, BE SURE TO MARK THE SHAFTS TO PUT THEM BACK TOGETHER IN THE PROPER ORIENTATION!

What will happen? Vibration, they're balanced at the factory.