Re: [alfa] Re: alfa-digest V10 #150

["The Baylys" <dabaylys@xxxxxxxxxxxxxx>]

George,

The suggestion of using the laser level is a good one and something I
considered when I was looking at setting up an Alfetta driveline in a
spaceframe chassis. After all one cannot possess too many shop tools ! There
are certainly some cheap and accurate resources available to us which would
have been cost prohibitive or simply unavailable when our cars were new.

This chassis project is still in the back of my mind but during my
investigations I was advised by more than one 'expert' that having a
propshaft in perfect alignment was not optimum in the real world.  These
guys were referring to standard low-speed propshafts with uni-joints but it
got me wondering if the same wouldn't apply to an Alfetta propshaft.

The theory goes that the propshaft must be slightly off being dead
straight/square or it would induce harmonic vibrations to the driveline
under low power conditions (highway speeds).  The shaft should be offset in
a certain way dependent on the direction of rotation and power application.
Sorry, I can't recall which way it should be offset.

I'm not a qualified engineer and simply toss the theory out there for
consideration/discussion/disapproval.

Beatle
'67 Duetto
Oz
----- Original Message ----- 
From: "George Graves" <gmgraves@domain.elided>
To: <alfa@domain.elided>
Sent: Sunday, June 13, 2004 11:56 PM
Subject: [alfa] Re: alfa-digest V10 #150


> Alfetta drivelines will often do this if  the engine isn't absolutely
> level with the input to the clutch housing. I.E. if the engine output
> coupling is angled down because the rear mount of the engine has sagged
> and/or if the input shaft of the clutch is pointing slightly down, the
> drive-shaft might seem to have pulled them straight when all
> tightened-up but they aren't. On getaway, the torque of the engine
> against the stationary rear driving wheels will cause the drive shaft
> to momentarily 'jump-up' at the junction between the fore and aft shaft
> as both the back of the motor and the clutch take up the slack at the
> moment of inertia. The only way to check this is to pull the drive
> shaft and while holding a bubble-level hard against the triangular
> Giubo (doughnut coupling) mounting flange on the flywheel check the
> angle of the vertical spirit bubble; it should be dead-center or pretty
> damn close. Do the same with the giubo mounting flange on the nose of
> the clutch input shaft as well (without the giubos in both cases,
> obviously). An even better method would be if one has one of those new
> laser levels. Choose one with a perfectly square side directly opposite
> the light source. That way, when you hold the level flat against the
> engine output giubo flange, the laser beam ought to hit the input giubo
> flange on the clutch assembly dead center and when held against the
> clutch input shaft giubo flange it should hit the engine output giubo
> flange likewise, dead center.  If either are significantly out of
> level, that's your problem. There can be several reasons for this. The
> most obvious would be a bad motor or transmission mount but you say
> that they are all new, so I would suspect an incorrectly mounted deDion
> traingle assembly. It's either loose somewhere or something is bent. I
> really don't see how an engine with new motor-mounts can sag in the
> back, but perhaps the front mounts were incorrectly installed. Maybe
> one of your new mounts was defective out of the box (don't exclude the
> possibility of the hanger bearing being defective, either). Of course
> unless you measure the level of both the transaxel assembly and the
> engine you'll never know. I realize that this is a lot of work. The
> drive shaft is not easy to remove and refit, but you can't do it with
> the shaft in place.  Good luck and let us know what you find.
>
> George Graves
> '86 GTV-6 3.0 'S'
>
>
> On Jun 12, 2004, at 4:09 PM, alfa-digest wrote:
>
> > From: owner-alfa@domain.elided [mailto:owner-alfa@domain.elided] On Behalf
> > Of Mark
> > Denovich
> > Sent: Saturday, June 12, 2004 12:30 PM
> > To: Alfa Digest
> > Subject: [alfa] thumpin' milano (again)
> >
> > So I'm hoping for some insight from the digest with regards to a Milano
> > driveshaft problem.
> >
> > Symptoms:  On a hard launch (not tire squealing, but quick) the
> > driveshaft seems thump against the tunnel, felt as if it was under the
> > E-brake console.  Otherwise no driveline issues...  very smooth.
> >
> > What I've checked done:  During the engine swap to my new Verde (last 8
> > months or so) I replaced the following:  all engine mounts, all donuts,
> > center support, all transmission mounts, poly dedion bush...
> >
> > I've been underneath, and it all looks good and tight.   The
> > transmission mounts have not separated (yet) and I don't see any
> > clearance concerns.
> >
> > I really don't know why my driveline is getting so out of line...  any
> > guesses as to where I should look next?
> >
> > - --Mark
> > The Alfa Wiki: http://alfa.denovich.org
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