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.
---
- Barney Gaylord <barneymg@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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