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59 Posts
Discussion Starter #1 (Edited)

I have a 1967 GTO and it has a GM 12 Bolt in it out of a 1972 GTO. It is making a clacking noise sometimes from the rear and I think (maybe?) it is because I have too much axle end play. This started fairly recently. At first I thought it was a loose lug nut, it sounded like the washer was jostling back and forth between the lug nut and the Cragar rim but it's not that, I checked all lugs several times.

Here are the measurements I gathered this evening :

Axle play on passenger side = .040

Axle play on drivers side = .045

C-clip thickness is = 0.131

C-clip button end slot (where c-clip goes) = 0.145 (just installed new Strange 30 spline axles with new bearing and seal because I thought they would fix the issue, they did not fix it)

Center pin differential thickness where axles touch it is = 0.612

Do these gaps seem like they would cause this clacking noise I hear? I was considering getting new c-clips from Tom's Differential that are .143 thick to take up some of the slack. What about a new center pin, should mine be thicker than 0.612 ?

Other suggestions to debug this?




898 Posts

good morning
or at least morning for sure

I am not a differential guy
I have had real bad bearings on my axles b4 on my 10 bolts in years past
I dont ever remember a clacking sound per say

I had a differential rebuilt twice becuase if a clicking sound that would drive me nuts
at slow speed that would go away at 20mph in my 86 chevy 4x4
did brakes first still there did axle bearings still there
rebuilt the diff thinkin that swiss watch posi from GM was about to grenade nope
still there
u joints nope .definately coming from the rear under the truck
I finally had the shop owner drive my truck and I walked along side ,,,

yup coming from the wheel ... pop the wheel off 15x10 6lug Boydd alloy rims and 35" goodyears
I asked if we could rotate the tires andcheck the lugs and rim center

as he rolled the tire out to me for inspection
I heard clink in the tire

funkin a ... the dip sheet that mounted my new tires didnt install new steel valve stems at goodyear
when I had my 1200.00 MTRs mounted so when I asked why when I picked up my truck they replied
my old ones were fine... I said NO I requested new as I know the rubber washers deteriate on the steel valve stems
and they had been on the wheels for 2 sets of tires....

dip sheet left one of the rubber seals and its washer inside the tire when he replaced the valve stems as I waited after hours for him........

cost me over a grand for that bull krap..........

just sayin dont overlook the easy stuff I guess ..............


things that come to mind youve probably already checked

u joints
ebrake cable hangin up on front of driveline
brakes too tight
springs all correct
correct differential lube
had any work done at goodyear lately ?
squeeky hubcap or beauty ring center cap >

I hope you find it soon.... it looks like you have enuf light and access to make the job easier
seems carrier and axle clearances would be a clunk from side to side while driving

please keep us informed .........

59 Posts
Discussion Starter #3
Thanks BLK, I will check some of the items you mentioned and update this thread when I find the problem.

59 Posts
Discussion Starter #4
Well, I said I would circle back when I found the source of the clacking sound and I found it. I am posting this in the hopes that it will save some other poor soul the aggravation and money I wasted. I don't hear as well as I would like and could have sworn the sound was coming from the rear. This started me down a rabbit hole that entailed replacing both rear axles and my 67 being off the road for the better part of the driving season because I didn't trust it :(

It turns out the sound was coming from the front drivers side! I ended up taking off the tire and the dust cap that covers the nut that holds the hub on landed on the ground. I few taps with a hammer and it was snug again. Good grief.

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