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Hello,
so know that I’m on the road I notice a horrible clunk sound from rear when I turn. When I jack car up from rear (on load) and turn wheels forward/reverse I hear it. no Play side by side on drive shaft but a decent amount turning it before rear engages if that makes any sense lol.any ideas on what could be?
thank you
joe
 

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More info is required on your rear suspension and differential type in order to offer any useful suggestions. There should be very little play in the in the differential rotating assembly.

Norm
 

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Here is link to a set of 8.8 differential installation instructions.https://performanceparts.ford.com/download/instructionsheets/FordInstShtM-4209-8.pdf

Hope This Helps
Norm
 

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Never the less, the rear is not dry! I've used 75W90 Valvoline synthetic in many cars with no issues. Could be excessive clearance between the pinion and ring gear.
 

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Disconnect the drive shaft and see if there is "slack" in the pinion to ring gear mesh. IF you have to turn the pinion a bit before it moves the ring gear, you have lost your clearances somehow. Pinion shaft loose or broken, pinion bearing(s) shot, carrier bearings shot, carrier bearing main caps loose. Is this a posi rear end? That adds more possibilities . . .
IF it only does it during turning, check your spider gears.

Doc
 

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If there is excessive slack pinion to ring gear, check the torque on the pinion nut...it may stand a little tightening. Like Doc said, pinion shaft could be (slightly) loose.
 

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Those are not the best way to check for pinion preload. With a pry bar or screw driver, see if you can move the pinion in or out. If it moves, then you have lost your pinion bearing preload.
Normally pinion bearing preload will create a whine, that will change under load and cruise.
Your noise sounds like it would be sync ed to one revolution of the wheel or ring gear.
A ring gear bolt is a possibility, but without hands on it is just a guessing game.
 

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Clanking in corners with quiet in a straight line is usually a Detroit Locker differential locking and unlocking.
 

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My wife had an 86 5.0 GT years ago. The small (posi) coil springs in the carrier got loose and went between the spider and side gears. I replaced it only to have it repeat almost immediately. Bext I went to the later single piece spring and no more trouble. Pull your cover off and look inside. You’ll surely see the issue.
 

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Did you not drill and bolt the left lower Panhard mount? There is clearly no bolt but there should be.
Phil,
Buttinz’s car is a Mk3 which has a welded in panhard bar mount. The bolt in version came about with the Mk4.

Jeff
 

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Hello,
so know that I’m on the road I notice a horrible clunk sound from rear when I turn. When I jack car up from rear (on load) and turn wheels forward/reverse I hear it. no Play side by side on drive shaft but a decent amount turning it before rear engages if that makes any sense lol.any ideas on what could be?
thank you
joe
Agree that pulling the diff cover and inspecting is the way to go. A little work to get a lot of info.
 

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Discussion Starter #19
destroyed carrier. Burnt out clutches,fractured spider gears and slightly twisted axles. I’m have a strange 9” built with billet centersection. Rear is 6-8 weeks out so I am rebuilding the 8.8. I installed the Eaton trutac centersection just waiting for new axles to come.hopefully this week.temp fix to get car back out lol.
thanks
 
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