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Weird "clunk" when in gear and off the throttle

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Old 07-28-2022, 08:11 PM
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Car: 1988 IROC-Z/G92
Engine: 5.0
Transmission: T-5
Axle/Gears: BW 3.45 Eaton Truetrac
Weird "clunk" when in gear and off the throttle

Hello,

Curious situation here, prominently I notice this in 5th gear, however I would have to check again for the other gears.

If I am coasting, about 30 seconds after letting my foot off the gas, the car will sort of "surge" or "jerk" a bit as the engine speed is slowing down.

Only happens when in gear and coasting.

I have a tunnel mounted torque arm at the moment.

Any idea what the problem could be here?
Old 07-29-2022, 06:18 AM
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Re: Weird "clunk" when in gear and off the throttle

DFCO being deactivated?

RBob.
Old 07-29-2022, 06:36 AM
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Re: Weird "clunk" when in gear and off the throttle

Originally Posted by RBob
DFCO being deactivated?

RBob.
Im not familiar with DFCO, what is it?
I notice it does not seem to happen if its in neutral.
Old 07-29-2022, 01:30 PM
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Re: Weird "clunk" when in gear and off the throttle

DFCO (decel fuel cut off) is just that. On long decels from speed the ECM cuts the fuel to the engine. Then as the vehicle slows along with the engine slowing fuel is resumed. It is at this point the drive line can jerk. More so on a modified vehicle.

RBob.
Old 07-29-2022, 03:26 PM
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Re: Weird "clunk" when in gear and off the throttle

Originally Posted by RBob
DFCO (decel fuel cut off) is just that. On long decels from speed the ECM cuts the fuel to the engine. Then as the vehicle slows along with the engine slowing fuel is resumed. It is at this point the drive line can jerk. More so on a modified vehicle.

RBob.
Agreed.
...plus even a Tranny Mount in combination.
Old 07-29-2022, 04:25 PM
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Re: Weird "clunk" when in gear and off the throttle

Interesting! I imagine I notice it more due to the tunnel mounted torque arm?
Old 07-29-2022, 06:32 PM
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Re: Weird "clunk" when in gear and off the throttle

Originally Posted by T.L.
My guess is tranny mount..

Hmm, I just replaced this when I put the new torque arm on...

I wonder if it's loose or something. Ideally I'll be getting under the car when I get off tonight.
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