C6 Coastdown clunk.

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Joined: Thu Jul 24, 2014 10:24 pm
First Name: David
Last Name: Prior

C6 Coastdown clunk.

Post by actionmanmelb » Mon Aug 19, 2019 7:13 pm

Working on a late 60's Mustang with a 427 big block and a C6 auto.
Motor has been worked, has a moderate cam and as a result has low vacuum at idle.
Customer would like to get rid of annoying coastdown clunk when coming to a stop.
I figure that he is feeling the 3-2 shift as in theory the 3-1 or 2-1 should not be felt as the one-way would just over run.
Idle vac is about 12 inches. I have connected a vacuum pump to the modulator line and tried different vacuum settings.
The clunk is gone when the vacuum is over 14.5 inches.

Any suggestions as to fixing this?
David Prior
Action Auto Transmissions
Melbourne, Australia.

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Posts: 1139
Joined: Mon Oct 28, 2013 3:43 pm
First Name: David
Last Name: Hritsko
Location: Walton Hills , OH

Re: C6 Coastdown clunk.

Post by dhritsko » Tue Aug 27, 2019 10:52 am

they make a modulator for low vacuum , I believe the black stripe 36160B is the one
Dave Hritsko
Transtar Industries
Technical Service Manager

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