>>>My Bronco, as well as another I know of does this same
>>>thing. When taking off from a stop, as the back end of the
>>>Bronco goes down, there is a clunking from the rear, if you
>>>give it a bit more gas and the back goes down more, it'll
>>>clunk again.
>>>
>>>I have, however, removed the rear driveshaft and verified
>>>that the double cardon and rear u-joint are a-ok. I have
>>>just put the whole thing off as being the leafsprings, as
>>>the axle twists on them, they move and bind slightly,
>>>causing the sort of clunk, as the axle twists. If you
>>>notice next time, it feels like it is binding, and then when
>>>it gives, it makes the noise, and happens in steps.
>>>
>>>If anybody else has experienced this, and knows the cause
>>>FOR SURE, and how to fix it, SPEAK UP!!! Thank you
>
>

THE FIX TO ALL MY CLUNKS !!!

I also have a Ford bronco 1991. 218k+ miles. When ever It
>makes these clunking sounds I have the drive shaft rebuilt.
>I also see where a gentleman mentioned removing his
>driveshaft to check for end play. I also did this and found
>the drive shaft joints to be tight as can be. However you
>can't possibly simulate the same stresses that the rest of
>your drivetrain puts on the driveshaft which is several tons
>of torsional twist. It is only under these severe conditions
>that your drive shaft components will make sounds or show
>fatigue. Also make sure that you use an extremely high
>quality EP grease with no soap bases of any kind. The reason
>for this is that greases with these soap bases tend to wash
>out of the bearing when subjected to any kind of water
>submersion leaving your U-joints or other bearings
>completely unprotected. adamk1974
>

 

Mine makes a clack as i come to a stop. What it turned out to be is the frame twisting due to the added torque of the lift. The frame kinda flexes, and then releases, which makes the most god-awful sound youve ever heard. Dunno if its related at all, but thats my clanking contributions.

 

[updated:LAST EDITED ON 11-Nov-02 AT 01:51 AM (EST)]Ok, guys. I don't know if has been mentioned yet but the constant velocity (double cardon) U-joint has a centering ball and spring operation that can and does (source of my clatter, clank, clunk, etc.) wear and allows the driveshaft to jump around under high torque situations i.e. take off from dead stop. The centering ball and spring keep the two U-joint cardons (spiders as some refer to them) in centerline with each other hence allowing there to actually be three pivot points in the rear shaft without the need for a support between them. When the centering portion wears the weight of the shaft causes it to drop when not spinning and thus creating a binding until the centrifugal force of the spinning shaft compensates for the "sag" allowed by the worn centering ball and spring. The clatter is the joints and shaft bouncing up and down until it reaches a high enough RPM to center up on its own. There are obviously a host of other possibilities but dropping the shaft and checking into this possibility is a matter of removing eight bolts. Ten minutes to save money, your sanity, and get the truck to shut up.

Please note that U-joints are more likely suspects but my machinist said that my U-joints actually weren't that worn. I had him replace everything anyway.

 

You CAN find a worn U-joint by hand - I've done it plenty of times. Sealed bearing U-joints are stronger & more reliable than greasable ones, and Spicer Gold is the best. A clunk from the rear is probably a loose pinion nut (it needs to be at about 250 ft-lb) or loose U-bolts holding the axle to the springs. I recently destroyed an axle tube that way.

 

It is definately a good idea to check the pinion nut as long as you are looking for the suspect of a clunking problem. I have had them come loose on both of my broncos. I even blew out the rearend on one of them, and that was an expensive repair for something that could have easily been avoided.

 

One very common cause of the big "clunk" on shifting from drive to reverse is a poorly-lubricated slip-spline in the driveshaft.

The best thing to do for this is to disconnect the axle end, fully extend the slip joint and grease it up good. The grease fitting alone doesn't do a very good job of getting grease everyplace you want it.
And the slip-spline can be completely worn-out, in which case you'll need a new driveshaft assy.
Regards,
- R