Manual Trans. Thud when shifting

georgiarocker

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My trans is currently in pieces at the dealership. Ordering BG fluid. I'll provide details soon.
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MegaMagneticStang

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I have an '18 ecoboost that i custom ordered from the dealer. noticed the "THUD" day 1. still have the thud when shifting into 1st 17k miles later.

if this is a "fixable" issue, that would be great, but I doubt it. i brought the car back to ford shortly after getting it for something (forget exact reason), and the tech manager almost immediately asked if i was there for the clunk sound in the trans. lol.

so clearly, this isnt "fixed" for all 18+ mustangs.... i think its like others say, just a getrag thing. prob because the gears are big, or machining tolerances, or some design flaw.
 

green97probe

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I have an '18 ecoboost that i custom ordered from the dealer. noticed the "THUD" day 1. still have the thud when shifting into 1st 17k miles later.

if this is a "fixable" issue, that would be great, but I doubt it. i brought the car back to ford shortly after getting it for something (forget exact reason), and the tech manager almost immediately asked if i was there for the clunk sound in the trans. lol.

so clearly, this isnt "fixed" for all 18+ mustangs.... i think its like others say, just a getrag thing. prob because the gears are big, or machining tolerances, or some design flaw.
I've had this thud with both of the S550s and both of the S197s that I've owned.

I think it is the joint in the two piece driveshaft making the sound.
 

chesster51

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Has there been any new developments or cures for the thud? My Bullitt has it and I hate it. So far I've installed: BMR dif lock out bushings, Steeda subframe bushing supports and stop the hop braces, MGW shifter, BG trans and dif oil, Whiteline trans mount insert. I discovered the counterweight/damper piece that is attached to a shaft on the drivers side of the trans. is wobbly and make noise. It moves back and forth everytime a gear is changed and is only attached via a drive pin through the shaft it rides on. I was sure this was the source and brought it in to dealer and told them what I thought it was and they replaced it based on my diagnosis with no further investigation. It didn't change anything. So I don't know if the damper is part of the problem or not. What I do know is the when I had the car on jack stands and had someone shift gears while I was under the car I found the noise was coming from this part everytime the shifter moved. It is external and looks to be fairly heavy, as most counterweights are, which seems to give it too much lateral play and wobbling. I've thought about removing it completely, but it would involve dropping the trans to have access to remove the drive pin. I'm also considering a one piece aluminum drive shaft, as has been discussed here that part of the problem is also excessiive driveline play. Anyhow, just looking for some updated input, it there is any.
 

shogun32

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foam rubber sleeve over the counterweight (think pool noodle)? But have you actually confirmed it hits something? Otherwise I suggest hearing loss, or turn the radio volume up a notch.
 

Enzo

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I think what’s causing this is when you trying to push the shifter into gear, the fork is pushing the synchronizer sleeve which that pushes the synchronizer towards the gear itself and when those two meet it’s causing the thud sound. So either the synchronizer isn’t biting good enough or the way it transfers fluid around doesn’t soften the blow when the synchronizer meets the gear.
 
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bnightstar

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My car has it but it comes and goes depending on air in the brake fluid. If your brake fluid is old / overheated the thud is really bad and the car is making jumps when shifting enough to be noticeable from the public on the race track. If I switch to new brake fluid and make sure no air in the system then the Thud is gone and the trans shift butter smooth. Once you overheat brake fluid again (it happens not only from brakes but because your clutch line is between headers) the thud is back. I would say based on this experience that this is Clutch related issue but I don't think is harmful in anyway. With that in mind I guess a metal clutch line + Castrol SRF brake fluid should solve this issue for most people in this tread. For the others who like me spend a lot of time at the track I guess we will need to bleed our brakes more often. I hope this helps.
 

aleccolin

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I my experience the thud is just a Getrag thing, my S4 does it too, and a full rebuild doesn’t even solve it. They’re just set up with more lash I I guess. BG fluid helped some, but ultimately I cured mine with a Tremec and a 1 piece driveshaft. There’s a reason they don’t put the MT82 in the GT350 or Mach 1.
 

bnightstar

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They’re just set up with more lash I I guess. BG fluid helped some, but ultimately I cured mine with a Tremec and a 1 piece driveshaft.
What are the parts needed for doing a Tremac swap ? Did you go with Magnum XL or with 3160 ?
 

aleccolin

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What are the parts needed for doing a Tremac swap ? Did you go with Magnum XL or with 3160 ?
I did a Magnum XL, Tilton clutch, MGW shifter, and QA1 driveshaft. There’s a whole bigass thread here with several of us that have done it. Not too bad, but not 100% plug and play either.

https://www.mustang6g.com/forums/threads/installed-a-tremec-magnum-xl-in-my-s550.115797/

Best bet is to go with Modern Driveline, Bowler, or Silver Sport Transmission and buy a whole package from one vendor.
 

1MeanZ

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If you haven't been into the guts of a manual trans, then I don't expect this to make sense, but I'll explain as best I can.

The thud is caused when the main shaft (and countershaft) inside the trans suddenly change speed. The synchronizers are pretty grippy and causes the main shaft to comply very quickly. If you've ever held the front of your bicycle up and spun the front wheel really fast and then grabbed the front brake really hard, that shock of the wheel immediately stopping is the same thing your trans is doing and that's the thud you feel.

To eliminate the thud going into gear from neutral, push the clutch in and wait a second or two for the main shaft to stop spinning at engine rpm before you put it in gear. Also helps if you more gently or slowly put the shifter into gear vs just quickly stuffing it in. Moving the shifter more gently allows the synchronizer to slip a little bit instead of immediately grabbing. The harder you pull the shifter the harder the synchro will grip the mating gear, resulting in an immediate change in shaft rpm causing the thud.

The thud is also sometimes present at other times, like the 1-2 upshift for example. Same situation, rapid change in RPM of the transmission's internals as another gear is selected.

I assume this has been articulated previously in this thread, but I have the answer and it was faster to just type it here vs sort through 82 pages of clueless BS and false information...
 
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