Slight thunk when shifting 6sp into 1st

[Aramis76]

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

Any manual transmission can be shifted without clutch or damage when done properly. (aside from full stop obviously)

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[GT 4 LC]

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.

Interesting to say the least. I haven't experience this as I have the REV MATCH on and down shift so I can't remember experiencing this issue. Maybe give it a try!!!!!!

 

[Dena]

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!

We rebuilt a 1950 ford pickup and the transmission didn't have synchromesh. My father passed it on to my brother and soon he was driving without a clutch. We know a truck driver and he talks about doing it as well.
I drove the pickup a little but didn't really have the time to master than transmission so I would agree, I am not going to try it on my mustang either. It probably wouldn't damage the gears but it would put excessive wear on the synchromesh clutches.

 

[P2]

My 2015 GT Premium 6 speed did this as well. It's nothing to worry about. If you don't like the "thump" then push the clutch in, wait 10 seconds and then shift into first. You won't hear/feel it then.

 

[dusman59]

Just thought. Ford is very adamant about fluid level in the MT. Make sure its at the proper level. For the transmission the manual specifies a fill level that is 10mm ± 3mm below the plug opening. Waiting 5 or 10 seconds for a smooth shift into 1st tells me something is still spinng. Maybe try changing the fluid to something like Redline.

 

[Instant Action]

Just thought. Ford is very adamant about fluid level in the MT. Make sure its at the proper level. For the transmission the manual specifies a fill level that is 10mm ± 3mm below the plug opening. Waiting 5 or 10 seconds for a smooth shift into 1st tells me something is still spinng. Maybe try changing the fluid to something like Redline.

I ran Redline oil in the transmissions of both my E92 M3’s and it really made shifting slicker than snot. I would love to use it in my MT86 trans but Redline doesn’t list a compatible oil for it yet on their website, but if and when they do it’s a no brainer to switch.

 

[JDR09]

My S650 GT PP also does this. Only from a dead stop to 1st; never in any other condition.

 

[Aramis76]

Totally normal.
Gear lash.
It's the transmission getting momentum from the gears spinning that loads up the driveshaft and that in turn loads up the differential.
Since the gear is engaged but clutch not released, it has no strength, but it still has enough torque to come rest against the gear.
I'm sure someone can explain it better with more mechanical terms.

All my rear wheel drive manual cars have exhibited this.

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