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Discussion Starter #1 (Edited)
Hi all,

I recently purchased a '78 Sprint (97,000 miles) with a fried rear giubo (see pixs) and could really use some advice. In replacing the bad unit, I followed a Haynes workshop manual. I also have one from Autobook. The two are pretty consistent. What I hadn't read until later was Michael Harris' and Paul Mitchell's recommendations on alfagtv6.com and all the talk of how easily the driveshafts can be bent during removal, leading to shaft vibration. Do I have shaft vibration? I'm not completely sure. More on that latter.

International Auto was out of stock on the rear giubo so I ordered the FD 187 from Centerline. The new flex disk was slightly different than the original. Specifically, on the side facing the front of the car and engaging the rear driveshaft, the diameter of the centering hole in the machined center section was smaller in diameter and would not accommodate the old pilot bearing. Also, a much deeper chamfer is used on the new part and reaches almost to the outer edge of the center metal section. The side facing the rear of the car and engaging the clutch yoke appears identical. A call to Centerline Alfa went something like this:
Joe-CA: "Are you sure the car has the original driveshafts?"
Me:"No, but I also have no reason to believe they are not"
Me:"Are you sure this is the right part FD187? It wasn't in a part box"
Joe-CA: "As long as you have an after mid76, then yes, it's the only rear flex disk we sell" (Really, what do the GTV6 boys do? I though to myself. Or pre mid 76 for that matter)
Joe also added "We sold 13 this year and have had no complaints" (Really!) and "You know these are very difficult to find anymore. You should be happy we have any." That last quote might be paraphrased but that is about what he said.

So, in my mind, its got to have that pilot bearing. The designers didn't put it in for their health. The bearing doesn't quite look like the one pictured in the diagram attached. It, and the centering shaft on the driveshaft are a bit longer. Also the rubber seal is not attached to the flex disk as shown but is smaller in outside diameter and an integral part of the bearing. It seals on the smaller of the two concentric shafts, not the larger one pictured. The bearing seems to be a roller bearing. Since the driveshaft spider and the clutch yoke don't rotate with respect to each other (one hopes not anyway), it is curious that such a capable bearing was used (instead of just a bushing for centering). Anyway, I decided to find a machine shop and have the new flex disc bored out to accept the pilot bearing. They called back later to say that the metal is way too hard and that even with a carbide boring bar, the part just couldn't be machined. They did mentioned that it might be ground but that would be $$$$ but they couldn't accommodate anyway. Oh, by the way, they lost the pilot bearing to boot! They were very apologetic. I was very pleased.

So, at this point, the flex disc was installed despite these reservations. Does it vibrate? I'm not sure. At idle up to 5000rpm it is quite smooth with the exception of between 2500 to 3000 rpm. Here there is some resonance, maybe a vibration, it's hard for me to tell since I have no baseline with this car or any drivetrain of this type. Road tests have not been performed to date as a brake master cylinder also needs to be replaced.

So what are my questions after such a long description (sorry about that)?
1) Does this driveshaft seem consistent with a '78?
2) Has anyone else had similar experience?(where are you 13 others with FD187s?)
3) Should I look for an exact replacement and now, a new pilot bearing?
4) If so, where?
5) I can have a bushing made up out of oil hardened steel that could be pressed into the new flex disc and machined to accept the centering shaft of the rear driveshaft. Is this the way to go?
6) Should there be absolutely no vibration between 2500 and 3000 rpm? Even if coming from the engine or an exhaust resonance? I don't have an accelerometer but say one was to place a cup of water on the dash. In qualitative terms, how turbulent would the water be? (No, I haven't done this . Just seemed easy to do)
7) If so, are the alleged vibrations consistent with a bent shaft or missing pilot bearing, or would these cause vibrations throughout the rev range?

I appreciate any suggestions or comments

Thanks.
Gerry
Rear Giubo - front.jpg

Rear Giubo - back.jpg

Rear giubo views v2.jpg
 

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with the age of the car, I would have the entire prop shaft sent away and balanced, also have the flywheel balanced. I plan to replace my donuts soon, and I wont mess around, the whole lot will go off to be balanced.
 

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Gerry,

A few days after I spoke with you, we discovered that 3 out of 20 of our last shipment of this part were incorrect. This is very frustrating to us, as they have the exact same manufacturer part number cast into them, but the center section is completely different.

Give me a call on Monday and we'll get you a replacement for the disc you have.

Joe
 

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Discussion Starter #5
I don't believe the pilot bearing is pressed into the donut. It's actually on the driveshaft. You car is not a transitional car, so there is only one choice of donuts. The one in your picture appears to be the correct one.
Thanks ossodiseppia!

It's good to hear your positive vote for the driveshaft being original equipment, or at least the correct hardware for a '78, based on the pixs of the original giubo.

With regard to the pilot bearing, maybe pressed isn't the correct term (maybe overstated). The fit of the OD of the bearing to the donut was tight however. I used a drift to carefully but forcefully drive the bearing out of the donut center whereas the donut and bearing assembly slid off the driveshaft centering shaft relatively freely.

Thanks for your input.
 

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Discussion Starter #6
Gerry,

A few days after I spoke with you, we discovered that 3 out of 20 of our last shipment of this part were incorrect. This is very frustrating to us, as they have the exact same manufacturer part number cast into them, but the center section is completely different.

Give me a call on Monday and we'll get you a replacement for the disc you have.

Joe
Great Joe!
How funny and serendipitous for you to happen by this post. I'll certainly give you a call Monday.

Boy, this sure answers a number of questions. But not necessarily all.

Is this probably the source of the slight 2500rpm vibration/resonance? Or might the shaft still be bent?

At this point, it seems reasonable to install the correct part and see how smooth she is.

And lastly, where can I find another pilot bearing. I couldn't find one in Centerline's catalog. Does anyone else have a source?

Thanks.
Gerry
 

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The vibration at 2500-3000 rpm seems O.K. I just had my driveshaft rebuilt/straightened, balanced ( 83 GTV6). I get a slight vib around 2500 but disappears around 3000. I'ts smooth all the way to 5000. If you want a good drive shaft guy that's reasoanable, try Franks Driveshaft in SF. He did mine after all parts were installed for about 150.00
 
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