Early GTV to late GTV driveshaft switch? - Page 2 - Alfa Romeo Bulletin Board & Forums
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post #16 of 48 (permalink) Old 04-25-2009, 09:33 PM
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As long as we're on the subjet of "****, I wish I'd tried that a long time ago" I had a 91 Spider that had a vibration that I just couldnt find. It would come and go. Replaced a ball joint, a suspect tie rod end, drilled and corrected the fact that the power steering gear only had two mounting bolts (what were they thinking, should be three of them), all to no avail.

Then I bolted on a set of track slicks and the problem went away. I ordered a set of Sumitomo tires and put them on and the car was then one of the smoothest Spiders I've driven. There was nothing wrong with the tires I took off and ran on a GTV (for many miles).

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post #17 of 48 (permalink) Old 04-25-2009, 09:35 PM Thread Starter
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Quote:
Originally Posted by 1166 View Post
How are your wheels & tires?
They're in good shape I think - but more to the point, when the car is run on jack-stands (its permanent status), if I take the wheels off, the vibe is still there. If I pull the half shafts out, it's still there.

Quote:
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...
It's got the polyflex busings all over - notably, both ends of the trailing arms and at the diff end of the T-bar. They're not those old fashioned hard poly ones - these are the squidgy blue ones, from Australia I think. Do you think that could be bad?

That's something new to think about.

-Richard
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post #18 of 48 (permalink) Old 04-26-2009, 04:58 PM
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...so with the car on jackstands and the driveshaft OUT - no vibration.

...and with the driveshaft IN - vibration.
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post #19 of 48 (permalink) Old 04-26-2009, 05:15 PM Thread Starter
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Today:
- reassembled the best driveshaft halves I have (all new parts and balanced as a whole)
- put that back on the car with the transmission output flange spider from my 1600 that seemed to have slightly less runout.
Tested it and....no change. Vibrates like a walnut-tree shaker at about 65mph (still on stands)

Then - checked that I do indeed have poly bushings at the rear, the conical ones in the T-bar to diff junction are poly - and the rear of the trailing arms are poly - but the front of the trailing arms are stock.

I don't have any stock bushings to swap in - so to simulate a bit more compliance I just loosened the big bolt through the conical bushing and tested that...no difference, still vibrating. The poly bush is still pretty solidly stuffed into the cone though.

Then did the same to the rear trailing arm bush-bolts - slackened them off and re-tested...no difference.

I still like this idea - so am toying with the idea of replacing the bushings properly. dunno, need a week of rest & relaxation at work not seeing the underside of this car.

One thing I noticed today was...I spun the wheels up to test and this time I switched off the engine and put my foot on the clutch to listen to it spin down...could definitely hear some sort of very soft knock, slowing with the wheels..seemed to be coming from the rear end, probably the diff - so this has me thinking about the diff again. I have, in the past, bought a used axle, swapped it in, found no difference and re-sold it...maybe I need to do that one more time with a known good axle.

cheers,

-Richard
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post #20 of 48 (permalink) Old 04-26-2009, 06:33 PM
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Can you have somebody else "drive" the car while you look underneath (very, very, very carefully and safely).

Have we also done both engine and gearbox mounts?

Best
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post #21 of 48 (permalink) Old 04-26-2009, 08:09 PM Thread Starter
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Hi Pete,

yes engine-mounts are new and I've replaced the rear gearbox mount twice.

In the past I've done what you suggest - set the drivetrain gently running and then gingerly look underneath - it all looks very normal, certainly no sign of the drivehshaft bucking up and down or anything like that. If I reach under from the rear and touch the diff's sump, I can feel the vibration - but then, you can feel it pretty much everywhere so that's not very conclusive.

What should I be looking for under there?

-Richard
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post #22 of 48 (permalink) Old 04-27-2009, 05:16 AM
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I know you checked it, but it still seems consistent with the pinion bearing to me, FWIW.

Paul

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post #23 of 48 (permalink) Old 04-27-2009, 04:40 PM
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I asked my father (an A grade mechanic for something like 50 years) about this and here are is comments:
Quote:
Originally Posted by PSk's Dad
Did I ever tell you the story of the 4 cylinder Commer truck I worked on in Whangarei. Well I went to work for the Hillman/ Commer agents after I came out of my apprenticeship. Another mechanic had done a pinion oil seal, previously. Anyway I got the job of repairing a cracked clutch housing. Got it welded put the truck back together and 3 weeks later it was back in with a cracked clutch housing. The driver then admitted that a vibration was there at certain speeds.what I found is that when the previous mechanic had knocked the pinion flange back in with a hammer he had burred the recess in the flange so that the driveshaft flange was not bolting squarely into it. Believe me it was only about a 20thou gap on one side of the flange but it created a big vibration.
Maybe the Alfa has a burr. or even an out of true flange and it can be minimal but it multiplies due to the length of the driveshaft. Just a thought.
I'd thus purchase or borrow a dial indicator and very, very accurately check both gearbox and diff flange run outs. I'd also double check the driveshaft flanges.

Best
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post #24 of 48 (permalink) Old 04-27-2009, 04:59 PM Thread Starter
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Hi Pete,

Hey I've been to Whangarei! I even sort of know how to pronounce it.

Very interesting story from your father. I did have the pinion seal done on this car - soon after I got it and by someone else when I wasn't able to work under the car (happy days...) . I do have a dial indicator and will have a go at the diff-flange measurement.

I have no idea how to measure the driveshaft flanges since they'd be flopping around on the end of the UJs. The gearbox drive flange is the 3-pointed spider thing, which I just swapped for no improvement, so if the problem is anywhere it's the diff-end.

I suppose the acid test would be to try a known good diff. There's a good one sitting next to this car on my perfectly vibe-free Giulia-Super, but I prefer not to dismantle things that are running well.....if I made that one vibrate I might just have to end it all.

Thanks for asking your father, much appreciated.

-Richard
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post #25 of 48 (permalink) Old 04-27-2009, 05:12 PM Thread Starter
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Quote:
Originally Posted by 1166 View Post
...so with the car on jackstands and the driveshaft OUT - no vibration.

...and with the driveshaft IN - vibration.
Sorry - I missed this on Sunday. I think I might have confused matters by talking about "half-shafts"

With everything on the car - it vibrates
remove the road wheels - vibrates
then remove the axle driveshafts (inside the axle tubes - I call those half-shafts..?) - still vibrates
disconnect the flanges at the center of the driveshaft - NO vibration
disconnect the transmission output flange - no vibration.

I'd love to be able to disconnect the driveshaft/diff flange and try it - but you can't really do that. My current best guess given my diff-suspicions is that there would be no vibration then either - but that's all hypothetical.

-Richard
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post #26 of 48 (permalink) Old 04-27-2009, 06:57 PM
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We haven't got a diff issue have we? ... re-reading the knock knock noise you can hear.

My GTV had 4 teeth of the pinion when I bought it . Maybe your pinion bearings have gone and the knocking noise is the rollers hitting the bit where the hardenings gone through the race?

Pete

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post #27 of 48 (permalink) Old 07-27-2010, 07:59 AM Thread Starter
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The saga

Those of you kind enough to have followed my multi-year tale of woe here might be interested in the latest chapter.

As a reminder, by April last year I had:
"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, 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...". By then I'd also tried lowering the (spacing) the transmission cross brace downwards to simulate the later brace...all the above made no difference.

later last year I:
tried a different rear-axle for the 2nd time i.e. this was the third axle tried...made no difference (noted to self "it's NOT the rear end...!" only less politely)

Tried the rear half of a different driveshaft - in other words different UJs, flanges, splines and tube on the rear half...made no difference

Then - I got all drastic, and pulled the entire engine/transmission - used the excuse to fully rebuild the engine with Richard Jemison cams (which feel terrific on the 20 miles I've driven them to date) and replaced entirely the transmission with a reconditioned unit. In other words - the car now has different transmission bearings, different output shaft and new 'olive' and is just plain new and...it makes no difference - still vibrates like one of those walnut tree shakers.

And - while I had that lot out, I replaced the motor mounts with new Heavy Duty Alfaholics models - because of a very interesting comment from Max Banks that he thinks these HD ones are now back to hardness of the old Pirelli mounts, and the regular ones you buy today are way too soft - that had me all excited because I could see soft mounts being the issue (it's such a low-frequency vibration that it has to be something big moving, like the motor/trans, and isn't a rattly/zingy metal-on-metal thing) - but of course...they made no difference.

And finally the new transmission of course has a new rear tranny mount. I couldn't decide whether to go newer (i.e. "hydraulic" mount with the voids) or older (much more solid, hole dead center) but in the end went with 'hydraulic'.....made no difference. One clue...When I have tried the solid mount in the past it may have improved the LF vibes but was unbearably zingy/buzzy.

So here are my remaining ideas before I dig a hole in my garden and lower the car into it.

- Rear trailing arms have standard bushing in front and blue-poly bushing in the rear - I could change those to stock (although I've tried to simulate that and it made no difference - but obviously it's not something you can really simulate)

- haven't tried a new front driveshaft section yet - bent flanges? Wouldn't the balance machine have seen that? (the support bearing and rubber carrier are all new - this is an old style center support with rubber horseshoe - tightening that or loosening it makes no difference - in fact tightening it makes it far worse)

- fill the voids in the rear trans mount with the yellow poly inserts from IAP (again) and see what happens - last time it vibrated (zingy engine vibes, not LF thrumming) like crazy so I took them out - but could be an indicator that too much compliance at the rear of the trans is the deep problem

- get a later (70s/80s Spider) transmission x-brace and try that - but as far as I know they only lowered the rear (having raised it by going to later bushing) - and I've simulated that by spacing mine lower - or was there any other geometry change with later mounts?

Then I'm out of ideas. Thanks for listening.

-Richard
1967 GTV - (object of hatred - hopefully temporary)

Last edited by GTV67; 07-27-2010 at 09:40 AM. Reason: spelling
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post #28 of 48 (permalink) Old 07-27-2010, 08:02 PM
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The 2 driveshaft pieces have to be aligned don't they?. Are we doing this?

What about the centre driveshaft support. Have we replaced that?
Pete

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post #29 of 48 (permalink) Old 07-27-2010, 11:23 PM
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could you not use a 1 peice driveshaft? also your gtv.. the old type.. front motor and trans or front motor and rear trans? i am running a 1 peice driveshaft in my spider..alumiumn( but i have converted to a t5 tranny) and the 1 peice is very smooth.. i made a 1 peice driveshaft( also the 1 peice steel driveshaft was lighter than the alfa 2 peice. when i had an alfa tranny in the car.. was not hard to make.. but i kept loosing alfa trannys,( input shaft bearings in the last one),it was very smooth in the car.. but you had to get the tranny and the rear end angle to 1 degree of each other.. to keep the tranny in line( the org.) new mount is very sloppy, so i addded a polly stiffener to the mount. kept the alfa tranny inline. then final adjustment on the angles.... went to a t5 design..

anyone can buy a Porsche, only Drivers drive a Alfa Romeo

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post #30 of 48 (permalink) Old 07-27-2010, 11:56 PM
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Quote:
Originally Posted by bianchi1 View Post
... but you had to get the tranny and the rear end angle to 1 degree of each other...
Impossible as the axle moves (up and down) as you are driving along.

The alignment issues with driveshafts are way over stated. When I built my last club race car I just pointed the gearbox so it looked like it aimed at the rear axle and then put a driveshaft in the gap in the middle. Never had a problem.

Yes you should have an angle so the UJ moves through a cycle but otherwise it just fills the gap between engine and rear axle.

Returning to this car: Have we watched the driveshaft as it is spinning and the vibration occurs? (safely, somehow)
Pete

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