Hey guys, I got this clunk when I take my foot off the brake after sitting at a light. I hung upsidedown out the drivers door to see what was happening. When coming to a stop, the whole diff housing pivots (pinion flange points more toward the ground), then when I take my foot off the brake the diff pivots back into place (pinoin flange perpendicular to the ground). I'm sure someone else has experienced this. Is this due to worn leaf/shackle bushings? This is buggin' me out.

 

Is it the whole axle assy moving up and down or is just the pinion flange doing this? Also, what rear do you have?

Barry

 

I've got a 9 inch diff. It's not going up and down, as the brakes are applied, the whole housing tries to roll forward. As I let off the brake, the rear-end goes back to the correct position.

 

I'm taking a guess and would say that maybe your u-bolts are loose or that the springs are weak? I've heard of this before, but I'm not 100% sure of the cause. Also have you been tough on the rear lately and maybe snapped the 2 spring pin bolts that hold the leaves together? They also lock the rear end into position also. I've also have seen the tops of these rust away. Just some guesses.

Barry

 

Bobby,

There are a few causes for this phenomenon that I know of.
Most common is broken spring leaves and or bad Big End (read front) bushings.

Next is incorrect, stretched or loosened U Bolts. By NOT using Genuine OEM FoMoCo U-Bolts, the axle tube "kinks" and it rotates under the U Bolts just as you describe.

OEM Us' have the radius flattened or missing off inside of the arc where it makes "U". Being "Flat" OEMs don't stress, kink, damage housing tube, but instead compress evenly all along the run of the
U Bolts' radius. This keeps spring perch tight & flat to spring leaf &
locating center bolt.

I'll add 2 more points to this. . . . If you make "BIG POWER" and use aftermarket, or non OEM U Bolts it is possible to "circumsize" axle tubes like you used a "tubing Cutter. It is a nasty experience you do not want to go through! It's one reason I use those link type traction bars, along with OEM Ubolts of course!.

Also FWIW, I will use used OEM U bolts from a salvage Yard B4 I'd use new non OEM, Aftermarket U Bolts. OEM FoMoCo are Grade #8 tensile strength, while some replacements aren't even grade#3 in the aftermarket.

If you did "Kink" axle tube, real deal repair is replace the housing and use the OEM Bolts. I have to go to a U-Pull-It yard & take a 30" X 1/2" breaker bar, a 6" or 10" X-tension, deep 6 point socket
& a fresh can of PB Blaster & unwind them. Junk yard dogs just torch them (what a waste!)
FBp
Next is broken welds on the perch plate itself.

 

Sorry guys, maybe I haven't given enough info. The rear-end housing, leafs and u-bolts are all stock. The housing is not rotating inside the u-bolts, the whole assy(housing, leafs, etc.) is rotating forward. In the sitting still position, on level ground, the rear shackles are leaned toward the rear. When I'm hanging out the door, under braking, I can't see the shackles, but I'm guessing they're probably in the straight up, verticle position. That's the only thing I can think would be causing this (worn shackle bushings). As far as I can see the front bushing on the leaf is still in the center of the hole that it sits in. Not sagged out.

 

I am experiencing a similar problem but mine occurs only occasionaly when I take my foot off the gas. The rear end makes a clunking noise. I have decided that it is a worn out ring and pinion: when I take my foot off the gas the deceleration takes up the slack and clunks. I haven't absolutely isolated it but I can turn the drive shaft probably 10 or 15* with my hands before the wheels start to move. I'll find out soon because I am getting a new axle assy and replacing u-joints.

 

It's common for the slop in your rear end to be the pinion bearing. THey are worn badly. I'll bet if you take the diveshaft off, you will be able to move the yoke and pinion up and down. When I worked at the Ford dealers in the 70's, I alway kept front and rear bearings, and races, crush sleeves, pinion nuts and pinion seals in my parts room on hand. We would do 3-5 of these repairs every week. If a ring and pinion is worn badly, usually it will howl on de-celeration and not under a load. Wheel bearings on a 9" will also make that noise. Sometimes it's easier and faster to get a complete chuck and swap it out.

Barry

 

Like I said, first, most common thing is bad big end spring bushings.
FBp

 

I have the same problem with the 8.8" on my 89 F150. I have taken it to every garage and shadtree mechanic I can find and none of them have been able to figure it out. The truck still runs perfect and it does not seem to get worse so I have just come to accept it. The only difference is that with mine you don't have to roll just put it in gear (switching from forward to reverse) to hear the sound.

 

THat's common in the later year trucks. If your rear has normal play and the u-joints are good and properly lubed, what you hear is the noise from the play in everything( dr.shaft yoke splines, rear splines. etc..) echoing thru the shaft tube. These new tubes are thin and some are even aluminum now. In the late 70's we had a TSB from Ford on the shafts in the Granada's making noise and also having a clunk. We were told to remove rear u-joint and drill and tap hole in the end to recieve a bolt. Then fill with speedi-dry. WE then sent them out to be re-balanced. THis would deaden the sound. These cars also had the 8.8 rear. Some were so bad that the tubes actually split the length of the tube wide open.


Barry

 

jj292,

FWIW, when FoMoCo came out with the last F100 in 1980, which became the F150 in 81 & up they stopped using their GREAT Ford 9 Inch Rear End ***'y. & opted instead to go with a Dana-Spicer, Rear Loading, Salisbury Style ***'y similar to the infamous Brand X 10 or 12 bolt rears.

Dana uses a slightly different design for "spider" gears, or more correctly carrier pinions in their non-traction device rears. Dana uses a radical parabola or convexed thrust washer as a shim, in between pinions and case, on their spider gear shaft. These tend to both distort & wear severly and fast.

If the back differential case cover is removed with vehicle in the air, the case can be rolled until you can see in it, if you hold one wheel and turn the free play out of the other, you can see these carrier pinions move on their shaft.

My 88 F150 has 1/16 to 3/32 an inch "slop" per gear so I end up with 1/8 to 3/16 play in carrier assembly. It translates to about 1/3 a driveshaft turn or rotation. Letting off at road speed in 4th or 5th = a hard clunk. Or in traffic, letting off, or accelerating both clunk at any speed in proportionate gear for speed I'm doing.

I repaired the problem in a clients truck by using a Bowtie Spider gear set, thrust washer/ shims & new shaft. I have not done my own however, because I will wait til it "pukes" & stick a real Rear under the truck. I can buy 9" truck rears locally for $100. That's less that the cost of parts to repair the stupid Dana Spicer!

PS: I only have 150K - 160K on the 88 F 150 total. It had good PM service, and all that, besides it's only got a 4.9L I-6 EFI engine and is nothing like the 460 in my 66 which has no rear end problems and well over 200K miles on the 9" behind it !

FBp

 

I figured out what is causing my clunk. My rear suspension is so worn out that it has pulled the slip yoke most of the way out. It kind of make me wonder if this is the right drive shaft though. It seems like ford would engineer it so that when the suspension is compressed the slip yoke would still engage a good bit of the output shaft. This looks like it is getting ready to fall out some time soon. I better get to work on the coil over rear huh.

 

Sometimes the C6 will not shift to low until you touch the gas after a stop. Makes a clunk as it goes in. Try stopping, starting again and stopping immediatly before the trans upshifts to 2nd. If on the second try the clunk is not present its your C6 doing it. Mine does this all the time.