Early GTV to late GTV driveshaft switch? - Alfa Romeo Bulletin Board & Forums
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post #1 of 48 (permalink) Old 04-20-2009, 10:53 PM Thread Starter
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Question Early GTV to late GTV driveshaft switch?

Next step in my multi-year quest to remove driveline vibration is to try another driveshaft.

(Because what's left when you've already tried new UJ's, new donuts, replacement transmission-output bushing, new driveshaft nose-bushing, new center support bearing, new center bushing, greased splines and nose bushing, balanced shaft once, then re-tubed(!) and re-balanced driveshaft again and it's STILL there... replacement rear axle, rear transmission mount, new engine mounts and rebuilt transmission and lightened gears...and it's phased correctly, and I always re-assemble it the same way it came apart).

In fact I should have tried this swap ages ago. But, the only other driveshaft I have available to try is from a 74 GTV with the beefed-up center bushing/bearing. There used to be a beautiful exploded diagram on the web somewhere of how the early and late driveshafts differed and how you could swap parts from one onto the other. Does anybody know where that picture might be, or could otherwise explain how to do that job?

Thanks for any advice,

Richard
Scotts Valley, CA
1967 GTV (on stands...)
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post #2 of 48 (permalink) Old 04-21-2009, 11:26 AM
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Is the vibration at engine RPM or road speed? Does it go away with the engine off an the car coasting?
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post #3 of 48 (permalink) Old 04-21-2009, 12:51 PM
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Richard, am I glad I'm not experiencing your anguish!!

It sounds like you've tried almost everything.

I have had some success on the pre 1969 chassis in working with washers or spacers to adjust the angle of the transmission to the driveshaft, IE: lowering the rear mount incrementally to put the transmission and driveshaft in the angle that they "like".

Hope this helps. George

George Willet


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post #4 of 48 (permalink) Old 04-21-2009, 02:20 PM Thread Starter
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Hi George,

Quote:
Originally Posted by George Willet View Post
I have had some success on the pre 1969 chassis in working with washers or spacers to adjust the angle of the transmission to the driveshaft, IE: lowering the rear mount incrementally to put the transmission and driveshaft in the angle that they "like".
That is helpful, and actually I think we've discussed this before. You confirmed for me that the more modern transmission-rear-bushing (also known as the 'hydraulic bushing') which is looser and has the inner sleeve offset downwards, causes the rear of the transmission to sit between 1/4" and 1/2" higher in the car, affecting the working angles of the donut and U-joints etc.

So I tried spacing the trans-mount downwards both 1/4" and 1/2" and neither made any difference I'm afraid - that was very disappointing because it was the best theory I had heard in a long time. I also liked the idea because the vibration does seem affected by the 'ride-height' of the rear of the transmission - I bought a set of those yellow, polyflex inserts that you can shove into the voids in the hydraulic bushing (thereby slightly lowering the trans) and the main problem..very low frequency vibration..did seem reduced - but newer and even more annoying buzzy vibrations from the engine/trans were introduced so I gave up - might be time to re-visit this idea again.

To the other question asked...This is road-speed related. The car is up on jacks with the rear axle on the stands to simulate correct diff-driveshaft angle. Very low frequency, very high amplitude vibration experienced at about 60mph+. It's hard to talk in the car due to 'thrumming' vibration - it's a bit like when you're on the freeway and the sunroof is open the wrong amount.

Some other experiments I've done - may trigger some ideas...
- Remove the rear wheels...still vibrates (i.e it's not rear wheel balance)
- Remove the rear axle half-shafts...still vibrates (nor is it a bad rear halfshaft)
- Remove the donut (ie disconnect the driveshaft)...no vibration (suggests the problem is between donut and diff, but the transmission is completely unloaded here, so the experiment is suspect)
- split the driveshaft at the center bearing (ie disconnect the rear half of the shaft...no vibration, but again, front half + trans is no longer loaded)
- Hoseclamps on the rear half...still vibrates, possible to slightly improve, and drastically worsen vibration, suggesting the problem lies here, but could NOT tune out the vibration altogether (this shaft is perfectly balanced off the car...so I don't like hanging hoseclamps on it, but I'm desperate)
- Put foot on clutch while vibration is happening - it does not go away.

I spoke to Dan Marvin yesterday, who told me a story of how he once bolted a driveshaft together wrongly and damaged a flange, and the shaft was never the same - and he ended up replacing it. Very interesting...the flanges (a little like grandpa's axe) are the only original thing I have left on the shaft, having replaced tubes, UJs, bushings and bearings. Maybe I just need a different axe.

again - any suggestions gratefully received. Thanks,

-Richard
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post #5 of 48 (permalink) Old 04-21-2009, 08:32 PM
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Does it still have the low-speed vibration it had years ago, or just the high-speed one? It seems to have moved up the speed range. Has the intensity changed over the years? Out of curiosity, can you get it in both 4th and 5th at the same road speed? Interesting what Mr. Marvin had to say.

Please let us know what finally fixes it. When I read all your old threads on the subject, others similarly afflicted never reported back the results of the board suggestions. I've never seen anyone suffer so long, and try so much to fix the thing. Have you considered calling a priest for an exorcism?

Good luck,
Paul

Gone but not forgotten: 70 GTV, 76 Alfetta, 82 GTV6 Balocco, Step front GTV race car. Current: Giulia Spider Veloce race car, 105.51 GTV race car to be.
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post #6 of 48 (permalink) Old 04-21-2009, 09:46 PM Thread Starter
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vibes

Hi Paul,

Quote:
Originally Posted by ciscotex View Post
Does it still have the low-speed vibration it had years ago, or just the high-speed one?
ahh, now, I was worried about this, that someone would go back and look at the old posts and discover incosistency in the reporting. I'll assume by 'low-speed vibration' you mean vibrating at low-roadspeeds (and not low frequency) and say that, it's there, but you have to be really concentrating (and be neurotic, paranoid and super-sensitized, as I now am and always will be) because it's such a low frequency plus lower amplitude that it's harder to feel. I think this shows that it's a first-order vibration...1 x the rotational frequency of the driveshaft. Has it changed? I don't _think_ it has, no.

Quote:
Out of curiosity, can you get it in both 4th and 5th at the same road speed?
Yeah I think that one was a rat-hole...I thought it might not be as bad in 4th, but it is. Yes it's at the same roadspeed in 4th or 5th.

Quote:
Have you considered calling a priest for an exorcism?
Tried that - didn't work either.

The more I think about it, the more I realize I need a different driveshaft to try. And yes, when I fix this, I will report it in painstaking detail.

-Richard

Last edited by GTV67; 04-22-2009 at 07:26 AM.
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post #7 of 48 (permalink) Old 04-22-2009, 09:39 AM
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Richard, more thoughts:

I think you said that you checked and replaced the steel pilot bushing in the front of the driveshaft and replaced it. Correct? I stick my finger inside and feel for any wear grove, and replace that bushing if necessary. Did you lube the inside of the bushing and have the rubber stop/seal that goes over the output flange nut in place?

Have you: 1) checked the diameter of the transmission outputshaft's "olive"? It should be .707" and round; and 2) have you checked to ensure that the output shaft isnt bent?

Are you using any kind of a "donut saver", or just the donut?

George Willet


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post #8 of 48 (permalink) Old 04-22-2009, 10:48 AM Thread Starter
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vibes

Quote:
Originally Posted by George Willet View Post
I think you said that you checked and replaced the steel pilot bushing in the front of the driveshaft and replaced it. Correct? I stick my finger inside and feel for any wear grove, and replace that bushing if necessary. Did you lube the inside of the bushing and have the rubber stop/seal that goes over the output flange nut in place?

Have you: 1) checked the diameter of the transmission outputshaft's "olive"? It should be .707" and round; and 2) have you checked to ensure that the output shaft isnt bent?

Are you using any kind of a "donut saver", or just the donut?
Hi George,

Yes the steel bushing in the driveshaft nose is brand new - no sign of wear in it that I can detect, but then there are almost no miles on it apart from diagnostic runs. Yes, I keep it well greased and the rubber grease-stopper is in place

The olive was replaced before I rebuilt the gearbox, so it has maybe 1000 miles on it - should therefore be round. But, no, I have never checked the output shaft isn't bent. The one thing I have checked is whether the output shaft flange (spider? - the three pointed flange with donut bolts at the tips) is bent - Just this weekend I put a dial gauge under each bolt and they seemed to be within about 0.015" of each other so I took that as being OK - but now I will check the olive is centered and not on the end of a bent shaft - good idea...do they get bent? I suppose it could be dropped on a shop-floor etc. I like that idea - I'll check that next.

No, no donut savers, just a brand new donut (the 2nd one I've tried).

Thanks George and everyone else for the ideas...please keep them coming.

-Richard
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post #9 of 48 (permalink) Old 04-22-2009, 11:19 AM
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How do the output shafts get bent? Pull out the trans with the front section of driveshaft on it and hold onto the end of the driveshaft. Maybe let it slip and have the driveshaft hit the floor. It will do a nice job...

The dounut must also have the washers under the nuts as you tighten them up. If they don't, you can have the nut bite into the AL on the dounut and twist it as you tighten, thereby twisting the dounut in ways it wasn't meant to be twisted . There are plenty of ways to screw up the easiest tasks...
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post #10 of 48 (permalink) Old 04-23-2009, 09:15 PM Thread Starter
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Not exactly easy to measure whether the output shaft is straight - or at least that the olive has minimal runout. The bolts on the flange get in the way, if I pull the flange out then the transmission fluid will run out - and I'm not sure whether the seal would ever seal again? If anyone knows a good way (or can suggest the perfect tool) to do this, please let me know.

but as far as I could tell with the dial gauge on a base and moving it around the bolts...it's straight. darn.

still need to try another driveshaft.

-Richard
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post #11 of 48 (permalink) Old 04-23-2009, 10:47 PM
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You may be able to borrow a dial indicator where the 'probe' moves back & forth as opposed to up and down. Then the bolts won't matter.

If the back of the car is higher than the front, no fluid will run out and yes the seal should be fine.

WHAT type of center support do you have. I have seen people with the early style (D shaped rubber) try to 'reinforce' it with all sorts of things (siliconed on fan belts...) - always to bad effect...
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post #12 of 48 (permalink) Old 04-23-2009, 11:08 PM
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Are you sure your exhaust is not expanding when hot and touching the body work or something, that will cause a vibration boom noise through a car.

Best
Pete

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post #13 of 48 (permalink) Old 04-24-2009, 08:34 AM
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Are you sure your exhaust is not expanding when hot and touching the body work or something, that will cause a vibration boom noise through a car.

Best
Pete
Or are the exhaust hangers too rigid, causing a harmonic in the chassis? (We're streching here, but trying to help ). George

George Willet


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post #14 of 48 (permalink) Old 04-25-2009, 08:56 PM Thread Starter
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Thanks for the recent replies - first of all, here's what I've done in the past couple of days.

The original topic of this thread was how to swap the center-mount parts from a newer drive shaft to an older one so that I could try a different driveshaft. While staring at both this week I realised that the tail section of the shaft, with both UJs and the spline-joint, is identical on both. So today I swapped that in - the only difference is 8mm bolt-holes on the later shaft (I think 69-71 they came with beefed-up center mount but still 8mm holes) - my car has a later limited-slip diff, so at some point was converted to all 9mm holes, thus this other shaft fit to my car when kludged together with the 8mm bolts (just for a 15 minute experiment..!)

Anyway, it made no difference whatsoever, this tail-section feels just like my other one <sigh>

So, this afternoon it was back off with this hybrid shaft and a closer look at the trans-output shaft, 'olive' and 'spider' (3 bolt output flange). Annoyingly, I realised I was wrong earlier when stating that I had replaced the olive when rebuilding this transmission. I was confusing it with another transmission I rebuilt. This one I had measured and found to be fine so stuck with it. I removed the spider and then could properly measure at the olive - diameter was 0.707" on the micrometer - and runout on the olive = zero, or maybe 0.001"...definitely not a bent output shaft (am I unique in being depressed that I don't have a bent transmission shaft??)

Then I compared the spider to one I have from an old 1600 transmission - measuring to see if it could be bent at one bolt or something. The one from the 1600 does seem to be more uniform, ie the outer radius of the bolts is very uniform - maybe +/- 0.002" ...whereas the one of the car is more like +/- 0.007. So I will re-assemble tomorrow with this 1600 spider - but this doesn't exactly feel like the smoking gun.

The exhaust idea - thanks for that, yes I've looked into that before. There is certainly nothing obvious touching the car. I can swing on it in all directions when cold and nothing touches. When the car's cold it has this problem right away...but!...I have noticed that at the start of a journey it sometimes feels good and has deteriorated by the end, which does suggest something soft heats up and moves. There are new bushings on the exhaust mount on the rear of the transmission, but right now that's disconnected for access and the vibes are still there. I know what you mean about low freq. resonance-type vibes from an exhaust problem, but this does feel more mechanically induced. Hard to explain, it's the way it comes and goes with wheel-speed as well.

Oh and the center mount is the old D-shaped rubbery type - very loose. I've tried tightening it up, and as 1166 suggested, it just made it worse.

So, the search goes one - please keep all the ideas, from obvious to crazy, coming.

Thanks,

-Richard

Last edited by GTV67; 04-25-2009 at 09:01 PM.
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post #15 of 48 (permalink) Old 04-25-2009, 09:19 PM
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How are your wheels & tires? I had one car with 9 month old tires that had a terrible vibration. It turns out a tire slipped a belt and was NFG. I spun the wheel with the car up and noticed the tire had a lump in it. Replaced the tire and all was fine again.

Bad tire?
Bent wheel?
Bent axle flange?

What bushings do you have in the car? A friends spider had ploy bushes in the trailing arms and it had an odd vibration. Replaced the poly bushings with stock and problem solved...
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