Thud sound
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Joined: Sep 2020
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Thud sound
1973 F100 4x4 4 speed. When I let off the clutch there is a thud. I can “feel” it in the pedal. Does not sound like it’s in the drive shaft. Any info where the thud is coming from would be great.
Grumpy goat
Joined: May 2017
Posts: 3,058
Likes: 594
My first thought is excess pinion backlash. But check your bellhousing to engine bolts, bellhousing to transmission bolts, transfer case adapter bolts, or if you've got a divorced transfer case you check the intermediate driveshaft.
Back to pinion backlash, it's fairly easy to check. Chock the truck, put transmission in neutral, grab the rear driveshaft and see how much it rotates in both directions. If that isn't it, you can do the same thing for the transfer case & transmission. Except this time you'll put it in gear, remove the driveshaft from the rear end only or jack the rear end off the ground, and then turn the driveshaft back and forth to check for excess play. Do that in all four gears.
Back to pinion backlash, it's fairly easy to check. Chock the truck, put transmission in neutral, grab the rear driveshaft and see how much it rotates in both directions. If that isn't it, you can do the same thing for the transfer case & transmission. Except this time you'll put it in gear, remove the driveshaft from the rear end only or jack the rear end off the ground, and then turn the driveshaft back and forth to check for excess play. Do that in all four gears.
Thread Starter
|
New User
Joined: Sep 2020
Posts: 22
Likes: 0
My first thought is excess pinion backlash. But check your bellhousing to engine bolts, bellhousing to transmission bolts, transfer case adapter bolts, or if you've got a divorced transfer case you check the intermediate driveshaft.
Back to pinion backlash, it's fairly easy to check. Chock the truck, put transmission in neutral, grab the rear driveshaft and see how much it rotates in both directions. If that isn't it, you can do the same thing for the transfer case & transmission. Except this time you'll put it in gear, remove the driveshaft from the rear end only or jack the rear end off the ground, and then turn the driveshaft back and forth to check for excess play. Do that in all four gears.
Back to pinion backlash, it's fairly easy to check. Chock the truck, put transmission in neutral, grab the rear driveshaft and see how much it rotates in both directions. If that isn't it, you can do the same thing for the transfer case & transmission. Except this time you'll put it in gear, remove the driveshaft from the rear end only or jack the rear end off the ground, and then turn the driveshaft back and forth to check for excess play. Do that in all four gears.
More Turbo
Joined: Feb 2020
Posts: 633
Likes: 84
From: AL
My truck does the same thing. It's got excessive pinion backlash,and also some wear in the slip yoke, allowing some movement there as well.
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Grumpy goat
Joined: May 2017
Posts: 3,058
Likes: 594
Good luck with it!
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