[Mgs] Drive shaft balanced

[melfrankus at carolina.rr.com]

Like Hans I have a 71 BGT.  My fellow MG owners have observed my mechanical ability and cautioned I would commit sucide with a wrench.  So when my UJ's wobbled and driveshaft wiggled, it was safer for me to just buy and install a whole new assembly.  The cost was under $200 from several available US suppliers and the exchange was straighforward, simple, quick and fairly idiot proof.  Mel.
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- Barney Gaylord <barneymg at mgaguru.com> wrote: 
> There are three different propshafts for MGA, and you didn't say 
> which model car. See here: http://mgaguru.com/mgtech/propshaft/ps101.htm
> 
> 1.)  Don't assume anything.  Always check the facts.  It there is any 
> perceptible freeplay in a U-joint replace it.  See here: 
> http://mgaguru.com/mgtech/propshaft/ps202.htm
> 
> 2.)  If it is a late 1500 or 1600 type with 2-piece propshaft (fange 
> at front), there might be wear and freeplay in the sliding spline 
> just aft of the front U-joint.
> 
> 3.)  The spline joint may also be assembled wrong.  Axis of the two 
> U-joints have to be aligned in same plane to avoid vibration,  See 
> here: http://chicagolandmgclub.com/driveline00/0404/drshafts.html
> 
> 4.)  It is possible to install an early 1500 propshaft with a mid 
> 1500 gearbox.  In that case the coupling spline is a mismatched size 
> and wil not be engaged far enough, which can cause very odd wear on 
> the spline.  That itself should not caue vibration, as the front yoke 
> is carried in a sleeve bearing that is same diameter for either 
> propshaft.  However, the short engagement length can lead to 
> premature wear on the sleeve bearing.
> 
> 5.)  The sleeve bearing is very commonly worn.  I suppose every early 
> or mid 1500 type gearbox needs to have the sleeve bearing repalced if 
> it has not been done before.  Running clearance is originally like a 
> crankshaft bearing, 0.002" on the diameter, or 0.001" clearance on 
> the radius for oil film.  When the sleeve bearing is worn the front 
> yoke of the propshaft can wobble around with exactly same results as 
> a loose U-joint (vibration).   The radial motion will also make oil 
> seals fail prematurely.  When the sleeve bearing is badly worn it can 
> make the propshaft yoke and gearbox tail housing catastrophically 
> self destuct (same as having very loose crankshaft bearings).  If the 
> front U-joint is tight but the yoke moves, then the sleeve bearing 
> needs to be replaced.  See here: http://mgaguru.com/mgtech/gearbox/gt104.htm
> 
> Barney
> 
> 
> At 11:01 PM 9/8/2012 +0200, Hans Duinhoven wrote:
> >....
> >After some tests at several revs of the engine and speed I finally 
> >found, that some vibrations between the speed of 50 and 70 m/h are 
> >caused by I think an unbalanced driveshaft between the gearbox and 
> >the differential gear.
> >What is the cause of this?
> >Can this be rebalanced and if so - how?
> >Is it easier to replace the driveshaft with a used one instead of 
> >rebalancing the one, which is on the car?
> >....
> 
> At 09:17 AM 9/9/2012 +0200, Hans Duinhoven wrote:
> >.... the vibration is in for many years ....
> >....
> >Play in the UJ's is always verified as part this safety test, so I 
> >assume the joints are ok.
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