Manual Trans. Thud when shifting

[Buhbuhj]

not planning on buying a manual, dont currently own one

however

i have seen the video of the stock diff bushings slopping around. any chance thats the source of the problem?

This is from a couple pages back but I installed the BMR diff lockout and it actually made the thud louder. So the rubber was actually helping to mask the shock through the driveline.
My tranny has been getting louder since it's getting colder and I'm going to be putting in some RP in hopes it quiets it down a little. Also going to try the Steeda insert to see what it does with the thud.

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[dallas70]

At idle, there isn't any pressure pushing fluid through the trans, it's a lubrication bath.

The clutch may be fully disengaged, but input shaft of the transmission may still spin in neutral until a mechanical resistance is applied (shifting into first) due to aerodynamic forces inside the clutch mechanism. If it's in neutral with the clutch out, then you push the clutch in, the input shaft will still spin for a time because it carries some rotational inertia, until you slam it into first.

During all of this, one half of the synchronizer assembly is spinning at idle RPM (or slightly lower since you pushed the clutch in a half-second ago), and the other is stationary.

When shifting while the car is moving forward, one half of the synchro assy is moving at engine speed, the other is moving at wheel speed X Rear gear ratio.

The whole thud-while-shifting is not a transmission internal component issue, it has more to do with the stiffness of the transmission mount and shifter mount to the body of the car transmitting feedback from the synchro units back into the body and cabin.

Google "transmission synchronizer" to see the details of how these work. If someone has a better theory, feel free to put it forward. If you're having grinding, hard-to-engage gears, or missing shifts, then you have a problem. This is just a NVH issue inherent with the remote shifter design as far as I'm concerned. More likely a by-product of beefing up the shifter mounting design due to issues with the 11-14 cars. I also read somewhere that Ford had Getrag beef up the synchros for the '15, so there "shouldn't" be an issue there anymore.

New to this particular forum, but thanks for what looks like a good explanation of what's happening. I haven't heard of any real catastrophes related to this transmission thud scenario so I'm not worried about it anymore. Thanks for the details.

 

[5ABI VT]

It's definitely related to the synchros and or the input shaft of the trans. Here's a simple thing people can do to produce the 'thud':

Car on idling in neutral clutch disengaged. Push in clutch and go to first right away. = thud

If you push the clutch and wait 3 seconds, the input shaft in the trans which was previously engaged with the clutch and spinning at idle .. Slows down and stops. Push into gear = totally silent.

 

[mjribeiro]

I have the thud in 6th gear, as soon as I release the clutch.

 

[Asharus]

probably because it had to drop your revs significantly when u shifted from 5th to 6th

 

[fogus]

Very separate issue than what we're experiencing. We get a thud when we push the stick into gear before we release the clutch.

 

[gsxr1300]

If I wait a sec before putting it into first there is no thud.

 

[Asharus]

same with all of ours

 

[gsxr1300]

Then close this thread. Lol

 

[Asharus]

nah, we gotta wait for all the 2016 owners to chime in saying that it's unacceptable, etc.

 

[fogus]

Then close this thread. Lol

What? We should wait 1s between shifts to make then smooth? Other cars don't require this. I'm getting fast at shifting now, and I don't want to slow down!

 

[gsxr1300]

No only when stoped and you put the clutch in wait a second then put it in first, no thud.

 

[fogus]

No only when stoped and you put the clutch in wait a second then put it in first, no thud.

We get this when we're moving also.

 

[Buhbuhj]

So I put some RP syncromax in my trans this weekend and also installed the steeda bushing. Pretty huge improvement. Thud is muffled if not completely gone in some cases and there's more feel through the pedal. Shifter is no longer notchy when cold as well(not that this has anything to do with the thud). Definitely recommend the bushing and if you have the time the fluid swap.

 

[mjribeiro]

I've put 500 miles on now and feel the thud in every gear. Interesting test to try. I get the thud going to first before the shifter even makes it all the way into the 1st gear slot. In fact I can make it happen without going into first at all. Move the shifter toward first but stop. You should get the thud.


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