"Thunk" on takeoff
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Read a book..
Joined: Mar 2012
Posts: 31
Likes: 1
From: Nashville
"Thunk" on takeoff
Hi everybody. I have an '89 F150 Custom, 302 2wd, AOD trans, H9 differential. For the past couple of years, I've noticed a little "thunk" when I would be taking off. It's gotten very noticeable now. Especially at takeoff, when the transmission shifts (unless I really let up on the gas as it's about to shift). The U joints are all less than 3 years old. Last week, I did trans fluid change (even though it had been less than a year since I last did it), and changed the differential gear oil. Still about the same. I've been hearing some differential whine over the past few months. Could it be the slip yoke, or more likely something inside the differential? Thanks.
Member
Joined: Jan 2018
Posts: 11,256
Likes: 1,770
From: Memphis, TN, Earth, Milky Way
Clean the stuff out behind & under the seat, and in the bed, and in the glove box.
Air up the spare, and tighten its holder.
(phone app link)
Check the engine mounts - at least one is probably broken:
(phone app link)
...and the transmission mount. Inspect the radius arm bushings:
(phone app link)
...and the other suspension bushings, and the body mounts, and the rear pinion nut, and read all these captions about the frame:
(phone app link)
When you're sure all that is good, if the noise is still there, open the diff:
(phone app link)
Air up the spare, and tighten its holder.
(phone app link)
Check the engine mounts - at least one is probably broken:
(phone app link)
...and the transmission mount. Inspect the radius arm bushings:
(phone app link)
...and the other suspension bushings, and the body mounts, and the rear pinion nut, and read all these captions about the frame:
(phone app link)
When you're sure all that is good, if the noise is still there, open the diff:
(phone app link)