Slight thunk when shifting 6sp into 1st

[Instant Action]

This doesn't happen all the time with my GT PP 6sp, but when I'm sitting at a light, dead stop with the clutch out and I push the clutch to the floor, I pause for a second and select 1st gear, there is a slight thunk, more felt than heard but the strange part is it doesn't feel like its coming from the transmission, more like its coming from the rear as if the car had a transaxle, which it obviously doesn't. This happens maybe 8 out of 10 times.

Anyone else felt this in their manual GT's?

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[Zig]

This doesn't happen all the time with my GT PP 6sp, but when I'm sitting at a light, dead stop with the clutch out and I push the clutch to the floor, I pause for a second and select 1st gear, there is a slight thunk, more felt than heard but the strange part is it doesn't feel like its coming from the transmission, more like its coming from the rear as if the car had a transaxle, which it obviously doesn't. This happens maybe 8 out of 10 times.

Anyone else felt this in their manual GT's?

Yes, the same.

 

[Dena]

Sometimes when you press the clutch in, the gears are still turning for a short while. If you catch it fast enough that will happen. The other possibility is there is a little drag in the clutch, just enough to keep things turning.
in the days before synchromesh transmission, you needed the gears turning at the same rate to avoid grinding when shifting. It wasn't as much of a problem upshifting but when you down shifted you had to push the clutch in, shift to neutral, let the clutch out, give it some gas to get the gears spinning faster, push the clutch in, shift into the lower gear and let the clutch out.
Yes it was a lot of work so many people learned how to shift without using the clutch by running the engine at the correct speed to avoid grinding.

 

[Instant Action]

Sometimes when you press the clutch in, the gears are still turning for a shot while. If you catch it fast enough that will happen. The other possibility is there is a little drag in the clutch, just enough to keep things turning.
in the days before synchromesh transmission, you needed the gears turning at the same rate to avoid grinding when shifting. It wasn't as much of a problem upshifting but when you down shifted you had to push the clutch in, shift to neutral, let the clutch out, give it some gas to get the gears spinning faster, push the clutch in, shift into the lower gear and let the clutch out.
Yes it was a lot of work so many people learned how to shift without using the clutch by running the engine at the correct speed to avoid grinding.

It was called double clutching and I’m old enough to remember having to do it. I assure you, the clutch has been in long enough for the internals to stop turning before I shift into first But it still happens on occasion.
I had a ‘72 Alfa GTV that you couldn’t just drop it into first gear from a standstill. I always had to shift into second gear before selecting first gear. It becomes second nature after the first month or so or whenever I got tired of hearing that crunch without doing so

 

[Dena]

It was called double clutching and I’m old enough to remember having to do it. I assure you, the clutch has been in long enough for the internals to stop turning before I shift into first But it still happens on occasion.
I had a ‘72 Alfa GTV that you couldn’t just drop it into first gear from a standstill. I always had to shift into second gear before selecting first gear. It becomes second nature after the first month or so or whenever I got tired of hearing that crunch without doing so

Then that leaves the clutch drags just enough to keep things spinning. Things fit pretty close in the clutch so that can happen and it's probably nothing to worry about. If the gears grind or you have problems getting it into gear, that could be an issue.

 

[DCS]

Sometimes when you press the clutch in, the gears are still turning for a shot while. If you catch it fast enough that will happen. The other possibility is there is a little drag in the clutch, just enough to keep things turning.
in the days before synchromesh transmission, you needed the gears turning at the same rate to avoid grinding when shifting. It wasn't as much of a problem upshifting but when you down shifted you had to push the clutch in, shift to neutral, let the clutch out, give it some gas to get the gears spinning faster, push the clutch in, shift into the lower gear and let the clutch out.
Yes it was a lot of work so many people learned how to shift without using the clutch by running the engine at the correct speed to avoid grinding.

I agree with this explanation. Both are possible.
My method from the "old days" was (and still is), to depress the clutch, shift into 2nd and then 1st. Then let out the clutch.

 

[Instant Action]

I appreciate all the responses, all these methods will work to keep a person from grinding gears going into 1st from a stop, but this muffled thud noise comes from the back of the car, not the trans.

 

[Dena]

I appreciate all the responses, all these methods will work to keep a person from grinding gears going into 1st from a stop, but this muffled thud noise comes from the back of the car, not the trans.

The differential has play in it so when the gear grabs, it takes the slack out of the drive train. The gears need to be shimmed for the proper surface contact or they sing. If you were to get your hands on the drive shaft and the car was in neutral, you might be surprised at how much the drive shaft flops around.

 

[highvoltage]

Normal. Mine does it randomly. It’s not a harsh thunk or a loud one. My S550 did it too.

 

[Instant Action]

Ok then as it seems repeatable to others, I'll just chalk this up to a normal Mustang noise like the infamous engine tick. Thanks everyone for participating.

 

[Instant Action]

The differential has play in it so when the gear grabs, it takes the slack out of the drive train. The gears need to be shimmed for the proper surface contact or they sing. If you were to get your hands on the drive shaft and the car was in neutral, you might be surprised at how much the drive shaft flops around.

I would agree with you if it happened as I let the clutch out but since it happens with the clutch in and there is no decernable clutch drag, I believe then it must be something else.

 

[SAL-E]

My 2019 GT did that. Nothing to worry about.

 

[REV745DH24]

Sometimes when you press the clutch in, the gears are still turning for a shot while. If you catch it fast enough that will happen. The other possibility is there is a little drag in the clutch, just enough to keep things turning.
in the days before synchromesh transmission, you needed the gears turning at the same rate to avoid grinding when shifting. It wasn't as much of a problem upshifting but when you down shifted you had to push the clutch in, shift to neutral, let the clutch out, give it some gas to get the gears spinning faster, push the clutch in, shift into the lower gear and let the clutch out.
Yes it was a lot of work so many people learned how to shift without using the clutch by running the engine at the correct speed to avoid grinding.

What??? …. Yes it was a lot of work so many people learned how to shift without using the clutch by running the engine at the correct speed to avoid grinding.

That would blow the transmission not using the clutch when upshifting the gears!!!! Never done that on my shifting in Mustangs!

 

[BrianJ77]

My '24 PP GT does this also. If the car is rolling even a little there is no thud. At a full stop it comes and goes. I've actually found a way to mitigate it by holding the clutch in for a couple seconds, and then slowly pushing the gear shift into first letting the synchros mesh slowly (this seems to lessen the frequency). If I'm in a hurry and push the clutch in and shift rapidly into first its gonna thud almost every time. I agree with the above posts I don't think it's anything to worry about. Transmission shifts smooth in all 6 gears (and reverse) and the rear end is quiet. You could have the service dept look at it, but in all likelihood they're going to say that is normal operation.

 

[Instant Action]

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