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79 Alfetta GT (Sprint Veloce)
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Discussion Starter #1
Trying desperately to truly complete our 30+ year 79 restomod I've posted about some here. Got new exhaust, and was ready to go have first real fun driving, but sigh - as the car gets load from clutch engagement or significant throttle once going, it's making a serious vibration/noise from the propshaft tunnel around the e-brake handle. So depressing.

We have maybe an hour total on the motor, and now 6 miles on rest. Running seemed smooth at first but has gotten increasingly vibrational, and now even to the point of this noise. Noise is removed and vibration settles some with low throttle, but still not smooth. Any significant acceleration through, and it's a scary sound/feel.

I'm mounting a plan of diagnosis and correction, and just wanted to validate it here and see if anyone has more guidance. I've read through all the topical posts on the board and they've been very helpful to establish a more complete knowledge base around the components and processes.

Facts:
  • Propshaft re-built as part of resto. Guibos, center bearing, etc. All OEM parts which were available in '89. Think done right, (all according to Haines manual), but not 100% certain about that at all.
  • So long ago we don't remember if we had it balanced at the time. It all sat for ~30 years (in good garaged environments)
  • Current installed inspection shows:
    • Front and middle guibos look good/new as they should.
    • Rear guibo looks new too, but can see some hairline cracks at the bolt joints.
    • No guibos look stretched lengthwise.
    • Middle bearing support is sagging from center noticeably; maybe more than one half inch.
    • Engine and trans mounts look good too; they were renewed.

Plan:
  • Remove the shaft and inspect completely for proper parts and configurations:
    • All parts in place as per exploded views from Alfa. All gaskets, bearings, etc. in good shape.
    • All guibo and bolt orientations correct.
    • Aligning bush/bearing in rear guibo properly fitting onto clutch shaft. Same at other joints.
  • Inspect guibos more closely and determine if age began breakdowns.
  • Inspect engine and trans mounts more closely and determine if age began rubber breakdowns.
  • Replace center bearing support.
  • Replace guibos and mounts as indicated (hate to refresh again what was refreshed 30 years ago)
  • Get shaft and new components balanced and blessed by a local driveshaft guy who has the equipment and experience with these shafts (we've got one in Bay area)
  • Reinstall carefully with attention to all orientations, bearing/bush fits, proper lengthwise fit, etc.
  • Pray for smoothness and check.
I've seen posts here about letting 6cyl driveshafts rev some and 'settle' with a loosened pinch bolt, and some ideas about doing the same with the guibo bolts (no pinch-bolt for this year). Would welcome further reports about that if anyone has any.

Any guidance welcome, including parts sources. Highwood and EB seem to have the guibos and cheaper than here. Got a $275 quote for rear guibo with bush from Alfa parts. Ouch.
 

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Trying desperately to truly complete our 30+ year 79 restomod I've posted about some here. Got new exhaust, and was ready to go have first real fun driving, but sigh - as the car gets load from clutch engagement or significant throttle once going, it's making a serious vibration/noise from the propshaft tunnel around the e-brake handle. So depressing.

We have maybe an hour total on the motor, and now 6 miles on rest. Running seemed smooth at first but has gotten increasingly vibrational, and now even to the point of this noise. Noise is removed and vibration settles some with low throttle, but still not smooth. Any significant acceleration through, and it's a scary sound/feel.

I'm mounting a plan of diagnosis and correction, and just wanted to validate it here and see if anyone has more guidance. I've read through all the topical posts on the board and they've been very helpful to establish a more complete knowledge base around the components and processes.

Facts:
  • Propshaft re-built as part of resto. Guibos, center bearing, etc. All OEM parts which were available in '89. Think done right, (all according to Haines manual), but not 100% certain about that at all.
  • So long ago we don't remember if we had it balanced at the time. It all sat for ~30 years (in good garaged environments)
  • Current installed inspection shows:
    • Front and middle guibos look good/new as they should.
    • Rear guibo looks new too, but can see some hairline cracks at the bolt joints.
    • No guibos look stretched lengthwise.
    • Middle bearing support is sagging from center noticeably; maybe more than one half inch.
    • Engine and trans mounts look good too; they were renewed.

Plan:
  • Remove the shaft and inspect completely for proper parts and configurations:
    • All parts in place as per exploded views from Alfa. All gaskets, bearings, etc. in good shape.
    • All guibo and bolt orientations correct.
    • Aligning bush/bearing in rear guibo properly fitting onto clutch shaft. Same at other joints.
  • Inspect guibos more closely and determine if age began breakdowns.
  • Inspect engine and trans mounts more closely and determine if age began rubber breakdowns.
  • Replace center bearing support.
  • Replace guibos and mounts as indicated (hate to refresh again what was refreshed 30 years ago)
  • Get shaft and new components balanced and blessed by a local driveshaft guy who has the equipment and experience with these shafts (we've got one in Bay area)
  • Reinstall carefully with attention to all orientations, bearing/bush fits, proper lengthwise fit, etc.
  • Pray for smoothness and check.
I've seen posts here about letting 6cyl driveshafts rev some and 'settle' with a loosened pinch bolt, and some ideas about doing the same with the guibo bolts (no pinch-bolt for this year). Would welcome further reports about that if anyone has any.

Any guidance welcome, including parts sources. Highwood and EB seem to have the guibos and cheaper than here. Got a $275 quote for rear guibo with bush from Alfa parts. Ouch.
I found a full set of the later giubos on eBay for $200, they appear to be brand new too.
 

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The only way I was able to smooth out my GTV6 driveshaft was to have it completely disassembled, have all perishable components replaced including the 3 giubos, center mount and bearing, both spherical bearings, and then have the entire assembly professionally balanced.
 

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79 Alfetta GT (Sprint Veloce)
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76 Posts
Discussion Starter #4
The only way I was able to smooth out my GTV6 driveshaft was to have it completely disassembled, have all perishable components replaced including the 3 giubos, center mount and bearing, both spherical bearings, and then have the entire assembly professionally balanced.
We're prepared to go that far, but want to look before we do since we did go that far in the restore and the only wear anything has is age. Age with no motion appears to have sagged the center mount and cracking rear giubo.

Having the car sit so long with everything fresh does appear to have affected some of the rubber components.
 

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So, if you rev the car in neutral in the garage then the vibration is also apparent?
 

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I’ve owned numerous transaxle cars from nice to clapped out. Replacing the components on a carefully marked driveshaft (front to rear) has always worked. I’ve never needed a balance. On my race car I even mixed and matched to run the Milano transaxle.
Id start by replacing the center bearing.
 

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79 Alfetta GT (Sprint Veloce)
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Discussion Starter #7
So, if you rev the car in neutral in the garage then the vibration is also apparent?
There's vibration from straight revving, but not anything like when it's engaged and under some acceleration. Load and acceleration and the flexing there seem to send things into shake mode. I want to test the engine mounts, but not quite sure how. I'm going to have someone look at them as I rev to see if they're stretching a lot or the rubber is separating from the metal in any way. The engine does not seem pitch or twist excessively when revving under no load.
 

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There's vibration from straight revving, but not anything like when it's engaged and under some acceleration. Load and acceleration and the flexing there seem to send things into shake mode. I want to test the engine mounts, but not quite sure how. I'm going to have someone look at them as I rev to see if they're stretching a lot or the rubber is separating from the metal in any way. The engine does not seem pitch or twist excessively when revving under no load.
If that rear engine mount is gone, the engine will torque backwards and decrease the distance between it and the transaxle and put downward pressure on the driveshaft. If you're under load, I'd imagine the engine is getting thrown back and doing that.
 

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Just a quick story. Many years ago I made a rookie mistake on my own car. After changing the center donut I managed to get the rear half of the tail shaft out by 120 degrees. Drove without much vibration until you opened the throttle and the car felt like it was going to vibrate apart. Took it to a specialist that helped me sometimes when I got stuck. He couldn't believe it was the tail shaft so we had a look at the clutch. It wasn't the clutch. It was indeed my mistake when I didn't match the tail shafts halves together.

Sounds like you have all your ducks in a row so I'm sure you will work it out.
 

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79 Alfetta GT (Sprint Veloce)
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76 Posts
Discussion Starter #10
I’ve owned numerous transaxle cars from nice to clapped out. Replacing the components on a carefully marked driveshaft (front to rear) has always worked. I’ve never needed a balance. On my race car I even mixed and matched to run the Milano transaxle.
Id start by replacing the center bearing.
Just a quick story. Many years ago I made a rookie mistake on my own car. After changing the center donut I managed to get the rear half of the tail shaft out by 120 degrees. Drove without much vibration until you opened the throttle and the car felt like it was going to vibrate apart. Took it to a specialist that helped me sometimes when I got stuck. He couldn't believe it was the tail shaft so we had a look at the clutch. It wasn't the clutch. It was indeed my mistake when I didn't match the tail shafts halves together.

Sounds like you have all your ducks in a row so I'm sure you will work it out.
A helpful anecdote, as your symptoms are exactly as your describing. I can't be sure it was all put together just right (I didn't do the work, and we've found other orientation issues in the resto), so we'll take it out and ensure everything is just as it ought to be going back in.
 

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79 Alfetta GT (Sprint Veloce)
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76 Posts
Discussion Starter #11
If that rear engine mount is gone, the engine will torque backwards and decrease the distance between it and the transaxle and put downward pressure on the driveshaft. If you're under load, I'd imagine the engine is getting thrown back and doing that.
I did have a look at the rear engine mount and it looked good but we'll give it a deep look and shake when we're down there. What you're saying makes sense. Of course something like this could have any 1-3 of a dozen possible causes.
 

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It’s the center mount. Get a new one and make sure you have the two mounting nuts down tight.
 
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I believe the center mount is the problem too... Their should be no "sag" in it. And you said yourself that you feel it at the E break....that's pretty much where it sits. And start looking for a new rear donut.. That crack will only get bigger with each drive....
 

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79 Alfetta GT (Sprint Veloce)
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76 Posts
Discussion Starter #14
Just a finishing post to this thread. Propshaft fully rebuilt and balanced in fully assembled state by 'Driveline services of San Leandro' (Bay Area). They'd dealt with 116 shafts before, but not this configuration so had to modify their machines which they did. I highly recommend them if you're Northern CA and have any sort of driveshaft needs.

Shaft much smoother, but still some low rpm (~12-1500) vibes and still a noise under load. Determined today that the shaft is actually bumping the e-brake mechanism when under off-the-line or strong acceleration load. Hard to know if the shaft is shifting position more than it should, or the e-brake stuff is in the way because mis-positioned on re-installation. May change trans mounts as they sat for 30+ years, and could be weak and others here have through bolt strengthened them. Anyway, I do want to thank the community for their thoughts and guidance here.
 

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79 Alfetta GT (Sprint Veloce)
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Discussion Starter #16
Do you live in the Bay Area? We should meet for a drive. I live in San Jose
I'm in Oakland, and we should do a drive together. Still need to sort a few issues out on this car, but would then welcome a Bay Area backroad drive.

By the way, do you know of experienced any Bay Area mechanics that still work on the old cars? I've spoken with Alfaman in Novato and may use him, but I'm wondering if any others that I might use. Really just looking for someone with a lift, knowledge of the cars to put another set of eyes on a couple of issues, specifically this vibration one.
 
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