Metallic "clunk"--please help!
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Metallic "clunk"--please help!
My 1988 F150 4x2, 302, AOD, 3.55 Limited Slip axle, 76,000 miles, has just started to make a metallic clunk (like a wrench hitting a pipe), which comes from the rear of the truck when I shift from park to reverse, or to drive. I had the differential rebuilt at 72,000 miles, and the dealer replaced two u-joints to try to fix this problem, but it persists.
Is there something other than differential and u-joints that can cause this, or is it possible that the recent repairs were not done correctly--ie. a faulty u-joint installed, etc.
Otherwise the truck drives fine, shifts through the gears well, etc.
I am taking the truck back on Monday to the dealer that did the previous work, so any advice would be very welcome. I have generally had good service from this dealer, and think they are honest and usually competent. Depending on what they determine, I am a bit tempted to ask for a complimentary service (like a free oil change, or tune-up) for the extra hassle of having to bring the truck back in for the same initial problem--does that seem reasonable?
Thanks for any advice.
Frank.
Is there something other than differential and u-joints that can cause this, or is it possible that the recent repairs were not done correctly--ie. a faulty u-joint installed, etc.
Otherwise the truck drives fine, shifts through the gears well, etc.
I am taking the truck back on Monday to the dealer that did the previous work, so any advice would be very welcome. I have generally had good service from this dealer, and think they are honest and usually competent. Depending on what they determine, I am a bit tempted to ask for a complimentary service (like a free oil change, or tune-up) for the extra hassle of having to bring the truck back in for the same initial problem--does that seem reasonable?
Thanks for any advice.
Frank.
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Joined: Jul 2003
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From: Colville, Washington
Frank-try putting the truck in neutral, setting the prak brake and blocking the wheels and then trying to rotate the driveline. If the driveline turns more than about an inch, the rear axle was done wrong, unless the u-joints are loose. I test by holding the driveline at the rear end and twisting. You might also check for axle mount/u bolt problems that allow the axle to move when pressure is applied.
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What the dealer said....
The dealer said that mechanically everything is sound--ie. differential, u-joints, etc., but the drive shaft apparently has a "fibre" or something inside (this information from a drive shaft specialist) which can gradually begin to separate in older vehicles. Apparently that can result in a metallic clunk when shifting into gear and putting the drive shaft under load. He said it doesn't usually get any worse, or do any damage; in a small number of cases, it does get worse, and then can cause vibration when driving, requiring a new/rebuilt drive shaft.
Does anyone know anything about this or have any experience with this situation?
The dealer did not charge me anything extra for this extra check/information.
Thanks,
Frank.
Does anyone know anything about this or have any experience with this situation?
The dealer did not charge me anything extra for this extra check/information.
Thanks,
Frank.
