Slight metallic sound when Auto shifts

So just bought a Mustang and noticed when the trans shifts into 3rd and I let off a bit at the same time the trans will have a slight metal sound (light chain being dragged on concrete for a split second) that I can hear through the AC vents. Is this the sound of my transmission losing 3rd? Should I find a used one and rebuild it just in case?

Update 10/5/17:
Second gear sounds like it has turbo. Downshifting when the transmission is warmed up makes audible metallic noises in lower gears consistently. I think I'm going to purchase a backup transmission with a warranty and start getting comfortable with the thought of swapping it out in a weekend.

stv_huff said:

So just bought a Mustang and noticed when the trans shifts into 3rd and I let off a bit at the same time the trans will have a slight metal sound (light chain being dragged on concrete for a split second) that I can hear through the AC vents. Is this the sound of my transmission losing 3rd? Should I find a used one and rebuild it just in case?

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Don't let off when you shift. 3rd gear bands are always the first to give out. I think because for some reason it needs a little more pressure to shift properly into 3rd. When you let off, the pump slows down. My 2nd to 3rd shifts tend to be a little slow under no and light throttle shifts. When the rpm's are up it shifts just as quick as the other gears. You might be getting hung up between gears without the pump pressure.

07 Boss said:

Don't let off when you shift. 3rd gear bands are always the first to give out. I think because for some reason it needs a little more pressure to shift properly into 3rd. When you let off, the pump slows down. My 2nd to 3rd shifts tend to be a little slow under no and light throttle shifts. When the rpm's are up it shifts just as quick as the other gears. You might be getting hung up between gears without the pump pressure.

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I'll keep that in mind. I was just coming up to a light when it shifted and got freaked out by the noise. Honestly it's not like I would do anything to fix it but if it is a transmission issue I would buy a backup first instead of buying another motor to build.

My trans sounds are getting worse. Original post updated.

Looks like your tranny is in self destruct mode. How many miles are there on the car?

Car has 60k miles.

When was the last time the auto tranny oil was changed ? Did you get the level checked ? If it's down in fluid, it will shift screwy. It may well be damaged. These 05-10 5r55s auto tranny's don't come with a normal dip stick, pita. I installed an aftermarket
(performance automatic) aluminum pan on mine, holds an extra 4 qts. Comes with a drain plug on the bottom. Dipstick is the locking type...come up by firewall on pass side. Big enough so atf can easily be added, if required. Swapped to RP synthetic ATF. Also added a JDM 5r55s catch can, gets mounted in the corner, on drivers side, near the firewall, but on the fender. The 5r55s when hard pressed, will heat up, the the atf pukes out all over the ground. And with no dipstick, you can't easily check the level. The dealer can, since 'dipstick' is on the bottom, it's a stupid oem setup. I also added a b+m auto tranny cooler, and plumbed it in series with the oem ford auto tranny cooler. I was trying to do everything I could to prolong the life of the 5r55s.

Pentalab said:

The 5r55s when hard pressed, will heat up, the the atf pukes out all over the ground. And with no dipstick, you can't easily check the level.

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The dipstick is the person who came up with that stupid idea.

stv_huff said:

Car has 60k miles.

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That's a low mileage for auto tranny problems to be occurring.