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MG MGA - Help - Ratlle at the rear

Help. I went out on Thursday and on pulling away from some lights the car developed a rattle. The rattle only occurs under acceleration and seems to come from the rear end of the car.
The rattle sounds like putting a metal tube against a 4 blade fan, my guess is it is running at a 2 - 4 beats per wheel rev.
At high speed, coasting and light acceleration it is okay(only the usual rattles
Today I took apart the drum brakes and found nothing loose and I checked the exhaust was nowhere near anything where it would rattle. I then continued my investigation by removing the diff which seemed the only thing left. On inspection there is no visible damage to the diff and no metal droppings in the diff casing. There is just a small noise when I turn the input shaft coming from the bearing cover that seems to touch slightly the diff housing.
I am baffled. Any ideas more than welcome.

Neil
Neil

MGA 1500's through Decmber 1958 (and part of January 1959) have a sliding spline coupling between gearbox and propshaft. There are two models with different splines. The early one is 1 inch 10-spline, later one 1-1/16 inch 10-spline. See photos here: http://mgaguru.com/mgtech/propshaft/ps101.htm

The early propshaft has a welded dust cup surrounding the gearbox rear seal area. The later propshaft has a stamped steel dust cup with a small bell flange in front. This dust cup is press fit onto the propshaft front yoke. If it comes loose is can rattle around and make noise, especially at low speed. With the right conditions the dust cup will sometimes re-seat itself on the front yoke and stop rattling for a while, particularly at moderate road speed. The cure is to tap it back into place and add a couple of tack welds at the sides between the cup and yoke.

This is the most common MGA gearbox and propshaft, covering about 40,751 cars.
Barney Gaylord

Barney. Thanks for the tip but I have the later style propshaft fitting. I looked in a parts book and see what you are saying but unfortunately it is not the answer to my problem.

Still wondering.

Neil
Neil Purves

Two more 'thoughts':
1. Could it be the muffler knocking against the fuel tank?
2. How's the U-Js? My TR-2 used to knock on the tunnel under hard acceleration. Yes, they have to be pretty bad to do that!!!
Look for 'rubbing' points between gubbinses. Stuff that's apparently far apart in static conditions get very chummy under running conditions.
Cheers! Fraser
Fraser Cooper

I traced a strange noise that only happened under acceleration to a too long seat belt bolt, the ones into the tunnel. As the back axle moved it brought the prop shaft up far enough to just touch the bolt. The clue was the paint scratch that ran round the shaft.
Malcolm Asquith

The noise sounds like UJ knocking but UJ's are in good order. I will look further for any marking.

Neil
Neil

I know this seems unlikely.........
I had a rattle that was hard to find - and discovered it was my rear license plate vibrating in the holder.

Bent the plate and holder a bit and fixed..........
S
Steve

Another 'thought'. I was talking with some friends yesterday (Triumph owners!). Coincidentally, they mentioned a similar noise which was eventually traced to an engine mount. Seems the engine would rock enough under acceleration to cause a knocking from the rear of the car.
Fraser Cooper

This thread was discussed between 10/06/2006 and 12/06/2006

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