Knock knock knock...
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Mountain Pass
Joined: Oct 2010
Posts: 155
Likes: 1
From: Marin County CA
Knock knock knock...
Hi folks. I have a 1965 f100 with a rebuilt 352, 3-speed C-6 transmission and 9-inch rear end. Recently I noticed a ticking sound when I was turning hard left from a dead stop, but didn't think much of it. Now there is a steady knocking coming from the rear end. The steady knocking is present when I coast in neutral with the engine off. It appears to synchronize with the drive train and not the wheel rotation... about two knocks for every wheel rotation. It sounds like tapping on a body panel. I had the rear brakes inspected and everything is solid. The knocking Igoes away when I brake moderately and when I accelerate. There is also a noticeable vibration on deacceleeeration above 20 MPH. I'm likely going to bring her to a local transmission shop next week for inspection but was wondering if anyone here had an quick fix, opinion or.armchair diagnosis? Thanks in advance! --Rob--
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Mountain Pass
Joined: Oct 2010
Posts: 155
Likes: 1
From: Marin County CA
Checked u-joints and seem tight and I don't have any drive shaft supports. I'm taking it up to a drivetrain Specialist in Santa Rosa Friday Morning, hopefully it's something simple.
Laughing Gas
Joined: Oct 2015
Posts: 992
Likes: 114
From: Dallas, OR
It's kind of hard to see in the picture, but that looks like it has a bolt on cover on the back of the differential- that would make it a Dana, not a 9". On a F100, it should be a Dana 44 if I am not mistaken. I know the Dana 60 was used in later years, but I'm not 100% sure with the slicks.
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Mountain Pass
Joined: Oct 2010
Posts: 155
Likes: 1
From: Marin County CA
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Mountain Pass
Joined: Oct 2010
Posts: 155
Likes: 1
From: Marin County CA
Will do, didn't think of that! The u-joints look fine upon visual inspection, and I'm considering swapping in new ones just to complete the process of elimination. The rapping sound has decreased but is not gone. The noise is coming from the drivetrain but for the life of me I can't pinpoint it. I've has several mechanics scratching their heads too. Walking along side the rig coasting in neutral with the engine off, there is a thump thump that coincides with the rotation of the drive shaft. There is a slight but visible shutter at the rear of the truck that also coincides with the thumping. The vibration at deceleration has also decreased, but is still noticeable.
Laughing Gas
Joined: Oct 2015
Posts: 992
Likes: 114
From: Dallas, OR
Good plan. The other bearing can't be far behind in wear and Murphy says it will fail when you are farthest from home or on the hottest/ coldest day of the year. Probably raining too. 
Usually wheel bearings are more of a constant humming rather than a thunk sound, so that one is a bit of a surprise to me. Glad you were able to sort it out.
Usually wheel bearings are more of a constant humming rather than a thunk sound, so that one is a bit of a surprise to me. Glad you were able to sort it out.
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Feb 2, 2013 03:54 PM