thumping under truck
Logistics Pro
Joined: Feb 2000
Posts: 3,955
Likes: 50
From: Mesa
thumping under truck
I have this intermittent problem. When I have to brake hard, as in almost lock it up, I get this thumping, thudding sound from under the truck when I accelerate agian. You can actually feel it in the floor. It's almost like someone is under the truck with a rubber mallet. It happend a few times many months ago and then again this weekend. (I try not to have to brake hard) Once I get up to speed, it stops. At first I thought it was something in the tranny, like something didn't release. The first time it happened it really sounded like it came from there. But another thought is maybe driveline bind? Would this be possible if the braking action somehow rotated the axle downward and got the shaft out of line? I do have a little clunk when I take off normally so maybe my slip yoke does need lubed. I can reproduce the thumping by slamming on the brakes but honestly the noise scares the crap out of me. Otherwise the truck shifts & drives fine. Any ideas?
Post Fiend
Joined: Jan 2002
Posts: 5,859
Likes: 7
From: USA
thumping under truck
How many miles ?
I would lube the slip yoke. seems to be a common thing lately.
I'm assumming you chkd your u-joints and backlash in the rear dif.
any leaks around the pinon seal on the rear diff?
leaks are usually and indicator of rear pinon bearings begining to wear
thus the shaft seal starts to leak .
all your body mounts tight?
Just my thoughts
Rich
Ford Trucks Built Tough!
not with rocks
Watch out "X" Mayor of Truckville
I would lube the slip yoke. seems to be a common thing lately.
I'm assumming you chkd your u-joints and backlash in the rear dif.
any leaks around the pinon seal on the rear diff?
leaks are usually and indicator of rear pinon bearings begining to wear
thus the shaft seal starts to leak .
all your body mounts tight?
Just my thoughts
Rich
Ford Trucks Built Tough!
not with rocks
Watch out "X" Mayor of Truckville
Sit. Stay.
Joined: Oct 2001
Posts: 18,308
Likes: 20
From: Washington State
thumping under truck
Slip yoke.
Or someone tied a rubber mallet onto the bottom of your truck.
Your '99 more than likely doesn't have the updated driveshaft.
Check out what Rich said too!
Or someone tied a rubber mallet onto the bottom of your truck.
Your '99 more than likely doesn't have the updated driveshaft.
Check out what Rich said too!
Logistics Pro
Joined: Feb 2000
Posts: 3,955
Likes: 50
From: Mesa
thumping under truck
I did some searching and boy time flys when you're having fun. I found a yr old post where I was asking the same question. Been over 15k miles ago. Thanks for the tips. I'll grab a few beers and crawl under my baby and check her out. 
