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Discussion Starter #1
I've been slowing dialing in my long term resto project and have a decent amount of vibration in the driveline. I thought a rubbing exhaust was contributing but I fixed that and I still get some NVH.

I can't say that my scribe marks lasted the ~7 years it took to restore the car. I generally trust no shops and did just about 100% of the work myself. What type of shop would you look for to balance a driveshaft? I suppose its a pretty conventional driveshaft, right? Any vibration issues unique to the alfa?

I did replace the bearings and guibo I did not replace the UJ.
 

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There are darn few good driveshaft shops left. Find a place with a machine that runs as fast as possible. Truck shops are good, have seen it all, but their machines often are low rpm, because that's all trucks need. An Alfa shaft in theory can be turning 21% faster than redline, in fifth, if you have the power. A lot of machines don't go over 3000 rpm. Ask around, maybe with the big 4WD and hotrod guys, since they do a lot of modifying.

Andrew
 

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Discussion Starter #3
Thanks. Maybe a dumb question but physically how is a driveshaft balanced? Tabs welded/clipped on? Are there adjustments to be made @ UJ or bearing?
 

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The do straightness and balance. First they'll check the sliding spline is good, not sloppy. And the u-joints, not tight or loose. If all good, they put it on the machine, check it for runout, hit it to straighten it. Then finally dynamically balance, yes, welding on washers typically. They need the whole thing, donut, hardware and all. At least my shop does. Most of the shops around here have gone out of business, these guys in San Leandro do trucks, heavy equipment, farm stuff. They see all the BMWs, Alfas, Mercedes around and a fair number of hotrod specialty jobs.

Last job I had, my Super's spline was too loose, as were the three or four others I had lying around. They cut it off, welded in a standard American one that would fit within the tunnel. An upside is the front u-joint is now standard too, so any shop can replace it.

Andrew
 

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Discussion Starter #5
When you did this did you bring the car or just the parts?


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No, this is just a machine and fabrication shop, basically. You bring it all to them. If you're not capable of the work, I guess you'd have to go to a mechanic to remove it, then a second trip to the driveshaft shop. Forgot to say, when it's out is the time to judge the condition of the center bearing and its carrier. That's a toughie to replace, a very tight tapered fit. And like I said, the donut, and the condition of the centering bushing in the front piece, and the matching "ball" on the trans output shaft. You're looking for wear and off-center pounding.

Andrew
 

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Discussion Starter #7
Got it, thanks. I did replace all these parts but am now questioning their quality as I bought them many years ago from IAP before I ‘knew better’.

If anyone reading is in CT and knows a good shop, let me know.
 

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Well, with driveshafts it's not always the parts, it's often how the work was done. Changing u-joints can be tricky. Also, some u-joint kits that were sold by many places didn't really fit right. IAP was not alone, if in fact that's the problem. The bushing/ball fit on the output shaft can be very important. The donut just transmits the rotation, doesn't do the centering. If it's off center, no way it'll balance.

Also, I've had this shop do work, had to bring it back. Without a high speed machine and a patient mechanic, you can get less than perfect results. It's kinda thankless work.

Andrew
 

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Discussion Starter #9
Promising...

IMG_4573.jpg


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Discussion Starter #10
Yes understood its not strictly a ‘bolt on’ application of parts. I also include the trans mounts in that category and have been wondering if they have also been contributing to my slightly off exhaust fit on account of the trans to exhaust downpipe connection.


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A place that gives a hoot is a real find. Yes, hotrod guys. Could be pricey, but it's essential to be right or the car will bug the heck out of you.
Driveshaft issues to me are the most recurrent 105/115 mechanical problem.
Andrew
 

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Sure. The fit of the exhaust and the condition of the motor mounts comes into it. A first thing to diagnose is whether the vibration is road-speed related, or rpm-related. That separates it into the driveline (road speed) or engine/trans (rpm). Not always easy. I had an rpm-related buzz, in the rear axle, which was being transmitted by slight contact with the exhaust pipe.
Andrew
 

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Give Overland a try. I took my GTV driveshaft to them last year. A yard full of big rigs and the guys that work on them are the only ones that know anything about driveline work. They were unfazed by my tiny car parts. Turn around time was about a week. They’re in an unlikely location on a rural two lane miles from any truck route. I found them via a sign at Thompson Speedway.

Having said all that they didn’t cure my imbalance problem even after replacing the universal joints. I’m now waiting for the weather to warm up a bit so I can replace the giubo and rubber center bearing mount.

Mike
 

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Discussion Starter #14
Having read a few prior threads on driveshaft balancing I decided to check the phasing of the universal joints. Visually they look correct and I used my phones angle finder to confirm that at least to its degree of precision they are the same. Does everything look OK with regards to the bolts and orientation in my photos?

IMG_4644.jpg IMG_4645.jpg IMG_4646.jpg IMG_4647.jpg
 

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My big problem was finding a shop that could bolt up to the driveshaft flanges just to mount it in their machine. I finally found a shop that let me take their mount home so I could make an adapter to mount the driveshaft ends.
 

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Discussion Starter #16
Hey all I never got round to solving my driveline buzz but have been driving my car a bunch this fall and come to realize I have a particular resonance/vibration in 4th gear, at a given road speed that I do not have in other gears. Really not sure which direction that points me. I haven't used a mechanic for anything on this entire rebuild so I really do not know who in the New Haven area I would contact to look at the entire car, not just the driveshaft, w/r/t this vibration.

I suppose It doesn't hurt to have the driveshaft balanced as a first step, regardless?
 

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Hi Rus, Maybe something else to look at is if you used the correct transmission mount. I had a driveline vibration and swapped out my mount for the earlier type and the vibration disappeared.
 

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Discussion Starter #18
Thanks Pete. I am fairly sure I have the correct trans mount but I recall alot of confusion about which side the nuts, double nuts went on. I will photograph it when I disassemble the driveshaft to bring to the balancing shop.

I presume you aren't saying you swapped to early style as a 'mod' but that early style was correct for your early car?
 

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Discussion Starter #19
Pulled the dshaft and took some photos of the trans mount.
IMG_3106.jpg
IMG_3107.jpg
IMG_3108.jpg
IMG_3106.jpg
 

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Have you considered that you may have a driveshaft alignment problem? If it is out in either the horizontal or vertical plane it can cause vibrations. I quickly found a post about vertical plane alignment - https://www.alfabb.com/threads/prop-shaft-alignment.664854/#post-8285122
To check the horizontal plane alignment you hang three loops of thread each with a nut in the loop. One around the engine pulley, another around the gearbox output shaft and a third around the differential input shaft. You the sight down them to verify that they are in a straight line. Correction is made by slotting the holes in the tranny mount so that it can be moved from side to side.
 
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