Manual Trans. Thud when shifting

[D3adch1ld]

:lol:

The only place there should be backlash is in the rear diff (ring and pinion).There should not be extra "backlash" in the driveshaft. That's called a broken u-joint.

Thank you Paul. Lol!!!

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[SilverSpoon09]

So here is where I run into more issues. As I compress and Depress my clutch there is noticeable RPM venation. Even though I am FULLY pushing down the peddle till I hit the floor it seems as though it may not be fully disengaging. I also noted a slight noise related to this if the pedal is released all the way. I am curios if this is common across the platform and again pushing that slight jolt in the driveshaft. It seems we are all having a bit of engagement point issues and thus the helper spring removal to try and get a more linear engagement point on the pedal.

 

[SilverSpoon09]

Perhaps I misunderstood where the tech was saying the backlash and having researched it more it does seem to only apply to the mesh of the ring and pinion. I still am noticing a few related things and the thud I get is more related to a resonance of the body and cabin; much as though I were to put a old automatic into drive after rolling backward in neutral slightly. The driveshaft would then tightening up, sending that mechanical resonance through the cabin. This is a similar thud I notice but on a much lighter scale. Thus again, making me feel backlash may have something to do with it? Just brain storming going through the logical transfer of power through the drivetrain.

 

[D3adch1ld]

Perhaps I misunderstood where the tech was saying the backlash and having researched it more it does seem to only apply to the mesh of the ring and pinion. I still am noticing a few related things and the thud I get is more related to a resonance of the body and cabin; much as though I were to put a old automatic into drive after rolling backward in neutral slightly. The driveshaft would then tightening up, sending that mechanical resonance through the cabin. This is a similar thud I notice but on a much lighter scale. Thus again, making me feel backlash may have something to do with it? Just brain storming going through the logical transfer of power through the drivetrain.

Sounds like you might be experiencing something different than what we are saying. Manual transmissions are noisy, more so in a performance car. There are some very frequent noises we have established: 1) The 1st gear thumb, Solution: press the clutch for a sec or 2 before trying to engage the gear. 2) 2nd gear jolt, Solution: remove the clutch spring assist or learn the best engagement point with the spring in place. 3) Some vibration on the shifter is normal. 4) Grinding into 2nd or 3rd can be attribute to how new the transmission is, it takes a lot of normal driving to properly break-in a transmission. I've experienced this first hand on more than 4 race spec and built transmissions. Mating of the gears and gear aging make a transmission that much better.

If you are really concerned about the car, have the dealer inspect it or a trusted mechanic shop and they can tell you if you are reading too much into the noises.

 

[D3adch1ld]

To those wondering about the clutch spring removal, I did it today. It helped my second gear shift tremendously, also feels like the 3rd gear grind has disappeared. Its like I got to know my clutch for the first time, the feed back is phenomenal. Really a must for the car!!!

Please take notice that it will make your pedal effort 20-30% heavier than with the spring.

 

[Ruby305GT]

To those wondering about the clutch spring removal, I did it today. It helped my second gear shift tremendously, also feels like the 3rd gear grind has disappeared. Its like I got to know my clutch for the first time, the feed back is phenomenal. Really a must for the car!!!

Please take notice that it will make your pedal effort 20-30% heavier than with the spring.

That's a relief


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[Jason29]

How hard was it to remove?

To those wondering about the clutch spring removal, I did it today. It helped my second gear shift tremendously, also feels like the 3rd gear grind has disappeared. Its like I got to know my clutch for the first time, the feed back is phenomenal. Really a must for the car!!!

Please take notice that it will make your pedal effort 20-30% heavier than with the spring.

 

[D3adch1ld]

How hard was it to remove?

Even easier than the video, I press the pedal all the way to the floor and slid it out of the post, lol. Here's a good tutorial:

 

[Phlyguy]

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.

Shifting into second gear and then into first eliminated the "Thud" as the second gear synchro is stationery and for some reason the firsdt gear synchro seems to stop when in second gear. I know it's not the best solution but I have totally eliminated first gear "Thud" as a result.

 

[Jeffro]

Another "Thud" victim here.. Less then 500 miles on my magnetic grey Mustang GT PP. As soon as drop that knob into 2nd gear from 1st gear, "THUD" same from 2nd to 3rd. Tried higher RPM's and quicker shifts. Still hearing that lovely sound.. But I don't recall hearing it from neutral to 1st. I hate to say it but, I think I had a smoother shifting experience from my 97 5-speed Honda civic back from high school O.O

 

[Ruby305GT]

Another "Thud" victim here.. Less then 500 miles on my magnetic grey Mustang GT PP. As soon as drop that knob into 2nd gear from 1st gear, "THUD" same from 2nd to 3rd. Tried higher RPM's and quicker shifts. Still hearing that lovely sound.. But I don't recall hearing it from neutral to 1st. I hate to say it but, I think I had a smoother shifting experience from my 97 5-speed Honda civic back from high school O.O

Tried any of the suggestions on this thread? Assist spring?


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[dwaleke]

The assist spring has no effect on the thud.

 

[Ruby305GT]

And you are dropping the shifter into second before going to first? I'm not having this problem but I always had to calm synchros down by slipping into second on some of my older transmissions before dropping into first, so it's just habit to me.

Yeah but its 2015, not something we should be going through. We have an option for blind spot radar but have to shift into second before first to avoid a thud... :shrug:

 

[aeropaul]

Yeah but its 2015, not something we should be going through. We have an option for blind spot radar but have to shift into second before first to avoid a thud... :shrug:

You have an american RWD performance car with a manual transmission designed to sell for less than 33k and you're whining about a little synchro feedback... :headbonk::shrug:

 

[Ruby305GT]

You have an american RWD performance car with a manual transmission designed to sell for less than 33k and you're whining about a little synchro feedback... :headbonk::shrug:

40k as optioned. What i got it for, thats a different story. Come on Paul, you know all this could have been avoided with a different trans...

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