Mystery clunk

[Diseazd]

Just fixed another mystery clunk. My 72 (green) just developed the dreaded clunk. No problem, I've got a R/T mount so it's got to be the half shaft u joints. I pulled 'em off and had them replaced. Took her for a drive looking for a nice quiet ride......not. The clunk was still there. I put it back on the lift and wrenched the driveshaft around......must be in the drive shaft. While it was up on the lift, I checked for loose bolts. The mustache bar (two vertical bolts) were tight as a tick as well as the big control arm bolts. The two bolts from the back of the diff were pretty tight too, I could only get a quarter of a turn. I decided to drive her again before pulling the drive shaft to replace those u joints.......clunk is non existent. A tiny back off of the two diff bolts had caused a good clunk. Just a heads up to anyone who is blaming their clunk on diff, driveshaft or half shafts. Check torque on all major nuts in the rear......could save time and money.

[madkaw]

Yep,

I just posted this the other day. It only takes just less than a 1/2 turn on the diff mounting bolts to create a clunk. The ONLY way to tell is get a wrench out. I think folks like me that have had the diffs out on several occasions find that the STUDS are actually loosening causing the nut to be loose. Time to get the loctite red out and squirt those studs in place.

[Diseazd]

Right Steve.....that's what amazed me......barely a 1/4 turn of tightening.....it sounded like a bad u joint. I would never have thunk it! Good advice on big red.

[olzed]

I have a persistant clonk, so I'll be checking on my diff nuts.

Any idea what the torque on these nuts should be?

[ninjazombiemaster]

If I had a dime for every clunk my car made, I could afford to repair them....

[Johnny wick]

I have a clunk sound that appears whenever i lift the accelarator pedal at slow speeds. I believe it comes from the rear suspensión. Could this be transmission mount seal? I will take the car to the mechanic so he can lift it on the elevator. Any clues??

[Persimmon240]

olzed, 

 

My shop manual indicates that the "Gear carrier to rear differential mounting member lock nuts" should be torqued to between 54.2 and 68.7 ft-lbs - or, if you prefer metric, 7.5 to 9.5 kg-m

[Johnny wick]

So i must verify the rear differential mounting seal??? To be sure its tight enough?

[rcb280z]

Diseazd, when you say "clunk", when were you hearing it? I have a clunk sound now but not all the time. Mostly when making right turns, when there is less torque, while driving over uneaven rough roads, and those little round dome shapped lane dividers (don't recall the proper name). Trying to find where mine is coming from but already checked everything mentioned and then some. Even looked for a busted strut.

[Zed Head]

classiczcars people! jalexquijano has resurrected this thread, from dead.  The last post was October 2012 before he began resuscitation.  ~2.75 years ago.

[EuroDat]

jalexquijano, I think you should be checking all the bolts are tight and the diff mount for starters. If the diff mount is old it will sag and cause these kind of noises. The two big nuts on the back of the diff cover often cause this noise.

[Johnny wick]

Taking the car to the elevator this friday and will let all of you know!! Will take pictures while there!