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Discussion Starter #1
I have just recently bought a 1988 bronco and when I am driving down the road, if I let off the gas pedal it makes a clunking noise. I suspect that it could be bad U-Joints but I am not for sure. Does anybody have any idea of what it could be?

The Tennessee Warden
96 XL, 5.8L, E4OD, BW1356, 4.56 gears
2,813 Posts
I would try lubing the slip shaft on the rear driveshaft first. Do you get a clunk when taking off from a stop also? Remove the driveshaft, make marks with a paint pen or marker on either side of the slip joint so you can put it back together EXACTLY the way it was. Remove the dust cover accordion piece and throw a bunch of grease inside the slip joint and on the male end also. Then put it all back together. You can use zip ties to reattach the accordion dust cover, or the metal cinch clamps like OEM. If that doesn’t do it, it’s probably u joints or maybe an engine or tranny mount.

Super Moderator
23,882 Posts
Yo BroncoNamedReptar,

As MS88Bronc advised, Good info!

Driveshaft Slip Spline Lubed by Trucky18
"Inspect the driveshaft slip yoke seal for rips, holes or deformation. Replace if necessary.
Using a suitable cleaning fluid, clean all dirt from the driveshaft slip yoke internal splines and the driveshaft slip yoke. Carefully inspect the driveshaft slip yoke splines for wear or evidence of twisting. Check the operation of the driveshaft slip yoke.
Using a brush, coat all surfaces of the coupling shaft front slip yoke splines with Premium Long-Life Grease XG-1-C or -K or equivalent meeting Ford specification.
Using a clean long handle (stencil type) brush apply Premium Long-Life Grease XG-1-C or -K or equivalent meeting Ford specification ESA-M1C75-B, spread evenly on all the female splines of the driveshaft slip yoke."

"Place the vehicle on a frame hoist and rotate the driveshaft by hand. Check for rough operation or seized universal joints. If the universal joint shows signs of seizure, excessive wear or improper seating, scribe alignment marks on the driveshaft and rear axle companion yoke (or flange). Remove the driveshaft and remove and replace the universal joint. Install the driveshaft in the marked original position." by Ford
"The driveshaft should have very little rotation when in gear. Lock the transfer case or lockouts in to test the front shaft." by BigBlue 94

To check u-joints while the drive'shaft is installed, set the parking brake, chock tires, shift to neutral, and see how far you can rotate the transfer case output back & forth without moving the rear axle yoke/companion flange. Also see how far up and down you can push the driveshaft. Less is better.

"...DC is double cardan joint which is at the front side of the rear drive shaft. It's basically two ujoints couples together to allow more angle without vibration.
To check it; Jack the back axle up so tires are off floor.
Take it out of drive.
Go under and work the joint back and forth with your hands - there should be no play between one side of the joint and the other.
Also check the single ujoints on the axle side of the drive shaft.
If either have any play, you should replace them."

; "...could be a few things.. U-joints going out on the driveshaft, slip shaft needs greasing or 3rd member is warn and loose. get under and see if there is any side to side movement with the ujoints on the shaft, there shouldnt be any side movement at all; than grease your slip-joint (search) and go from there... by Sikedzombies
& by ElKabong, "When you check the u-joints as Spiked described, park it on a flat spot, block the wheels & put it in neutral. That way the driveshaft will be free to move if the u-joints are bad..."
(1988 Bronco Dealer Brochure

Free registration for some wiring diagrams (86 through 96) and Technical Service Bulletins, (80 through 96), same as by Ford @ BBB Industries- Premium Alternators, Starters, Power Steering Products | TSB's & Wiring Diagrams
Let me know if the registration/log-in process works for you becuse I can't, log-in anymore and they haven't respnded to my e mails.

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