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Discussion Starter #1
While driving home, I started to feel a weird feeling and shaking from what I think was the rear diff. It ran totally fine at speeds going up to 50-60 mph, but when I slowed down, it started to make a weird noise, so I just parked it for a day. The next day, I took it for a test drive. When slowing down and braking(around 5mph) the car started 'clunking'. I took the wheels off and the brakes look fine and there is plenty of oil in the diff. I put the rear end on jack stands and put it in 1st gear, 4th gear and reverse while running to to get the rear wheels moving to see if it would make any noise and any problems I can see and nothing.

Is there a test that I can do to see if the gears or my diff is messed up or another way to check it?

Thanks in advance!
Marc Andersen
[email protected]
 

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Discussion Starter #4
I hope that is the case as I know how to do a u joint and lube a slip joint... Differentials are a different story. Does it make sense that it would only do this on slowing down and not accelerating up to high speeds?
 

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considering the number of teeth, and the rpm of the differential, it would be more of a buzzing or vibration than a clunking. one clunk on slow down could indicate wear, a check for that would be to jack the car up and see how much slack between rotating the drive shaft and the wheels turning.
 

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Does it make sense that it would only do this on slowing down and not accelerating up to high speeds?
Classic symptom of a u-joint going bad.
When accelerating, the rear end squats a bit resulting in the u-joints having less of an angle to the diff. On decel, the rear unloads so the u-joint angles to the diff increase.
 

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Classic symptom of a u-joint going bad.
When accelerating, the rear end squats a bit resulting in the u-joints having less of an angle to the diff. On decel, the rear unloads so the u-joint angles to the diff increase.
Yup, I agree 100% with papajam. Focus on the driveshaft. Replace the Giubo too while you have things apart.

To answer your original question, one simple test for a differential is to drain the oil, and see if it contains any metal fragments. Fortunately, Alfa differentials tend to be pretty reliable as long as they are not allowed to run dry. The outer bearings will wear out over time, but they will signal that a problem is developing by making noise well before they fail completely.
 

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Simple test.
Fill the fuel tank, put some weight in the trunk and drive the car.
Did the symptoms change?
 

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Discussion Starter #9
OK, in looking at other posts, I will say that papajam has forgotten more about Alfas than I know, but there is no way in hell that he knew I was running on empty! I figured instead of filling up the tank and putting weight in the trunk, I just took all of your advice and just decided to replace the U joints, put lube in the slip joint and replacing the Giubo. I thought they are 25 years old, might be time to replace them anyway. With the new parts in, I just took the car for a spin and it runs like a champ! Jon, Alfacliff, Jay, Jim... You guys were right!

I want to thank you and all of the alfisti who contribute to this bulletin board. I have never met a group of people who are so helpful and provide such a wealth of information. Some times we never know the outcome of advice so I wanted to ensure you guys knew the outcome and a huge thank you comes with it. Now my soon to be 3 year old can ride in "fun car" again.
 
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