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Old 06-29-2020, 02:19 PM   #1
WannaBe68
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The Elusive KLUNK!

Has anyone ever found the problem of the mysterious KLUNK to be in any one of the input / output / adapter with the arrows in this picture - or a combination?
Tap the gas peddle on and off and the KLUNK from hell is still happening. All U joints are new, Transmission has fluid, tie rods/ends are tight, motor mounts are a year old... BTW - not my picture - I pulled it from another thread.
Thanks in advance!
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Last edited by WannaBe68; 06-29-2020 at 03:18 PM.
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Old 06-29-2020, 09:02 PM   #2
gmc684x4
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Re: The Elusive KLUNK!

I found my sm420 to rockwell tcase coupling very worn after i had a gear let go in my tcase took lots of scrounging to find anouther 420 setup

Detriot lockers when driven hard on the street can make a good bang too
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Old 06-29-2020, 09:48 PM   #3
WannaBe68
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Re: The Elusive KLUNK!

Sorry, I should have mentioned it's a stock th350 4x4 auto transmission/adapter/np205.

Thanks!
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Old 06-30-2020, 02:20 AM   #4
gmc684x4
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Re: The Elusive KLUNK!

Yes the parts differ
the way they couple is the same two male shafts connect with a female coupler in an adapter

Yes the adapters and shaft splines wear out over time and abuse

I think abuse is the bigger factor in wear and tear
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Old 06-30-2020, 10:39 AM   #5
SunSoaked
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Re: The Elusive KLUNK!

Please elaborate on the mysterious clunk. I have a mysterious clunk in my 85 K20. It's happened there times. Go to take off from a stoplight and when I give it gas....thud...and off she goes.

My truck is completely rebuilt with less than 1200 miles. New engine, rebuilt th400, rebuilt 208, new u-joints and inspected and serviced Dana 60/14ff w Detroit locker.

I'm stumped. When it happens, it's fairly hard and feels like it travels thru the frame.

I know Detroit lockers are noisy and all that. I'm just curious if this is expected from time to time? Is it just play in the locker that lets loose under certain conditions, i.e., creeping and stopping at idle then taking off?
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Old 06-30-2020, 11:27 AM   #6
WannaBe68
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Re: The Elusive KLUNK!

Well, my klunk isn't something I would expect to be normal. It happens when I put it in gear forward or reverse. When I'm doing about 10-20mph I can lightly push the gas pedal on and it klunks loudly...then let off on the gas pedal and it klunks loudly. The pitch is a bit higher than a klunk - metal pang is more like it. But I can do that to the gas pedal - on/off - on/off - on/off and it will klunk loudly with each on and with each off of the pedal.

I guess I'll have someone look at the coupler in the adapter.
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Old 06-30-2020, 02:21 PM   #7
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Re: The Elusive KLUNK!

Yes Detroit lockers are known to make noises on street usuage usually more of a bang hence Detroit bang bang nickname
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Old 06-30-2020, 05:33 PM   #8
Ironangel
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Re: The Elusive KLUNK!

What kind of backlash does the rear end have? That's where I'd look...
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Old 06-30-2020, 07:20 PM   #9
WannaBe68
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Re: The Elusive KLUNK!

The klunking was there before I had the rear end rebuilt/gears changed out about 6 months ago and that didn't fix it either. Thanks
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Old 06-30-2020, 08:01 PM   #10
sweetk30
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Re: The Elusive KLUNK!

my first 205 reman i didnt get the lash set correct on the idler gear set in the t-case and it clunks BAD . . . .

this will drive you nuts for sure . i do need to pull it and reset it before this winter .

posted in your other thread also .
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Old Today, 03:15 PM   #11
gmtech68
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Re: The Elusive KLUNK!

GM did have a problem for a while with the driveshaft slip yoke splines sticking but that would also make noise just after coming to a stop. A loose or separated engine or trans mount can do it.
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Old Today, 05:36 PM   #12
WannaBe68
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Re: The Elusive KLUNK!

Thanks gmtech68,
Still haven't spent any time underneath yet, but will soon - hopefully!

I've been to Devon! Spent a lot of time in Edmonton and Calgary and once played golf in Devon right there next to the river. I fly fished all over Alberta and had a few good days of fishing in the NS river not too far from Devon. Nice place!
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