Loud CLUNK going into reverse.

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Aug 6, 2012 | 06:50 PM

Nick Greer

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From: Athens, GA...it rocks.

Loud CLUNK going into reverse.

My 73 F100, 390, C6 transmission has a loud clunk going into reverse. When I move from reverse to any forward drive gear, the noise is almost not there...Any ideas what could be causing this noise, and if it's anything to worry about?

Ng

Aug 6, 2012 | 06:53 PM

77 2wd

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i have a 77 f100 with a 302 and c6, and it does the exact same thing, sometimes only when i put it into reverse and hit the gas right after, but doesnt do it on any other gear whatsoever

Aug 6, 2012 | 06:55 PM

mikeo0o0o0

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From: Stanley, VA

Check the U-joints but it could also be excessive backlash in the rear....U-joints, if bad replace. Excess backlash, I wouldn't worry too much about it.

Aug 6, 2012 | 07:02 PM

77 2wd

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well i know its not the u joints because, but whats the backlash thing?

Aug 6, 2012 | 07:05 PM

fmc400

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From: Austin, TX

Quote:

Originally Posted by 77 2wd

well i know its not the u joints because, but whats the backlash thing?

Because...?

Aug 6, 2012 | 07:15 PM

77 2wd

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oh haha i guess it didnt write it, but its because when i put my donor rear end i bought new u joints, because i had to change them because of the driveshaft, long story short, they're brand new

Aug 6, 2012 | 07:39 PM

PRIMERED79 SHORT BED

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Mine does the same thing, and i know for a fact its not a u-joint problem( just replaced them)

I have to agree its a backlash problem to, matter of fact my rear end makes noises now after changing the both rear outer axle seals and bearings and adding new fluid with the trac lock additive.

Shes just getting old.

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Aug 6, 2012 | 07:44 PM

mikeo0o0o0

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From: Stanley, VA

Quote:

Originally Posted by 77 2wd

whats the backlash thing?

Backlash is the clearance between the ring and pinion in the differential. Usually it's a few thousandths of an inch but years, mileage, abuse, etc. cause it to increase allowing the pinion to "bang" when put into gear.
Like I said, not something I would really worry about.

Aug 6, 2012 | 07:47 PM

#10

kobaltblue

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From: Sweet home Alabama

broken engine/Transmission mount with the hood up put it reverse watch the engine does it move?

A 4x4 you'd see the transfer case stick jump....2X theres nothing inside the cab to move.

Aug 6, 2012 | 09:36 PM

#11

bamaf150

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From: Mississippi

I've owned 2 of these trucks with automatics and both made the same clunk going to reverse and this when they weren't that old. I've heard many others all make the same noise, all automatics.

Aug 6, 2012 | 09:42 PM

#12

79FordBlake

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From: Wingo, Ky

I've drove many of these trucks with automatics and I believe part of the problem along with to much backlash is that they engage to hard into reverse to begin with.

Aug 6, 2012 | 10:19 PM

#13

bamaf150

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From: Mississippi

Quote:

Originally Posted by 79FordBlake

I've drove many of these trucks with automatics and I believe part of the problem along with to much backlash is that they engage to hard into reverse to begin with.

I'm inclined to agree, I have often thought it must be something inherent to the C-6