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I have a 289 4-speed conversion Can worn or loose motor mounts be the cause of a clunk felt and heard when starting of in first gear or reverse only.
Transmission is newly rebuilt by Toplaoder Heaven and the clutch is a new Centerforce.
Previous transmission that was installed did the same.
 

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If you have a broken motor mount then the engine will go up and hit the hood when you take off. That would make a clunging sound. I would take a serious look at that.

Look for paint rub marks on the hood or have somebody watch the engine while you put it in first and give it a bit of gas with the brakes on. That will be enough torque to make the engine lift, if that's what it's doing.

Ask me how I know.....................

Greg.
 

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Where does the sound come from?

If it's the back of the car it may be your gears are in need of attention.

It may also be u-joints. You would notice the problem primarily when taking off, as that's the only time you are not already moving.

It could be motor mounts too, but that would not likely cause a clunk sound, unless the engine is hitting something, but then it would not happen in both 1st and reverse. If you want to check the mounts you can put the e-brake on, open the hood, put the car in 2nd (1st works too, but the car will likely move) and gently let the clutch out while revving the engine. The driver side of the engine will lift if forward gears and the passenger side in reverse. If either side lifts you have a broken mount.

I would be inclined to say it's either u-joints or rear gears. Most likely u-joints.
 

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Where is the sound coming from? My '69 was clunking from the rear in 1st, 2nd, and reverse; turned out be be a broken exhaust holder. The pipe was clunking on the gas tank when I started up--easy fix!
 
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