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Discussion Starter · #1 ·
For a while I've been getting a slight thud when I leave a stoplight and sometimes when I initially release the brakes from a stop. U-joints and carrier bearing are new and in great shape. I did lube the slip joint with grease recently when I changed u-joints, it made no difference. Ring & pinion lash is within spec as well.

I read threads a while back where this was happening a lot but no one posted a definite cause. Is it the transmission getting worn (245k miles on vehicle) or a worn bushing somewhere? Many thanks
 

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Leaf springs slapping? Been a while since I had stock springs on my 6.0 so I don’t remember if they had the plastic spacers between the leafs. Check for broken leafs. If auto the tq converter will load drivetrain so all backlash would be taken up. Because of that I would focus on suspension.
 

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Discussion Starter · #3 ·
I have been getting a loud metal clanking sound from the rear when I go over speed bumps, wonder if that is related. I will check the leaf springs closely when I get a chance.
 

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2005 Ford F-250 Lariat Crew Cab FX4
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Could be the 4WD locker acting up. Do you have the ESOF or floor shift 4WD? Also could be front u-joints. My assumption is the thud sound is the 4WD hub locking and engaging and then disengage on its own. Maybe jack up the front and spin the wheels by hand to see if you notice anything unusual
 

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Discussion Starter · #5 ·
ESOF. Front shaft u-joints have not been changed yet but I have new joints ready to go in, will definitely check there. The thud is very subtle and is only felt and not heard, almost like some slack is being taken out of the driveline somewhere when I release my foot off the brake or take off gently.
 

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ESOF. Front shaft u-joints have not been changed yet but I have new joints ready to go in, will definitely check there. The thud is very subtle and is only felt and not heard, almost like some slack is being taken out of the driveline somewhere when I release my foot off the brake or take off gently.
Did you find the cause yet?
 

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Discussion Starter · #8 ·
Did you find the cause yet?
Not yet. Cab mounts are good since they were just changed by me last year, bushings in the leaf springs look good...maybe some micro cracking, nothing major. Rear sway bar end links seemed tight.

It is definitely in the driveline, like there is a little bit of 'slack' at certain times. I will change the front drive shaft u-joints when time allows, but I think it may be the transmission. I will pack even more grease into the slip joint for giggles, but doubt it will help. Who knows.
 

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I've read that the slip joint on the driveshaft can be picky about which grease/lube it likes
 

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Front shafts should have nothing todo with this, unless you have the hubs or T-case locked in

Check the U-bolts , spring leafs for cracking, spring hangers, shock mounts -- looking for rust streaks on the brackets, as a sign of movement
 

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Discussion Starter · #11 ·
I've read that the slip joint on the driveshaft can be picky about which grease/lube it likes
I'm about to the point of squirting expanding foam into it and shoving it back in quickly.

Thanks Hydro, no cracks on the leafs, will check closely for movement.
 

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My f250 was foing what sounds to be the same thing with only 24,500 miles. I askedthe group and came with a ton of possibilities. I change carrier bearing and all three u-joints with grease fittings and lubed slip joint. Seemed to stop.Left Astoria Oregon to Greenbackville Va literally Ocean to Ocean 4200miles the route we took.Now a year later the thud or bump is back not as bad but I can replicate it with the throttle pedal. I think maybe slip joint needs lubed again as I used a high dollar waterproof marine grease(that's all dude had at his shop he was letting me use).Hope this helps.....Popi
 

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Often the cause is the driveshaft slip yoke needs a new Teflon grease coating formulated especially for it.

Liquid Fluid Font Drink Gas
 
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Jack
Greetings. Thank You for Sharing. I will try to find a tube for the next upcoming Lubing! Hey if you are ever on my side of the pond would admire to buy you lunch sometime and of course glean all the wisdom that you are willing to Impart. I live very near Chincoteague Va.
 

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There may be other things that are causing it, but I solved it twice on two different trucks doing that.

The grease is expensive for what it is. When I had my deep discount years ago, I bought the can of it.

The brain cells with any knowledge are dying off quickly.
 
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