Clunk in drivetrain when I shift under load from 1-2 or 2-3

[lazarus870]

16 GT PP with the PP2 tune. All stock otherwise.

When I drive normally there is that THUD when I clutch in or shift gears that I can feel from the rear end. But when I am driving under a bit more of a load or let it rev up to a higher RPM and I clutch in, it feels like a much bigger THUD like I got rear-ended or something. Sometimes even when I am in first gear crawling through traffic and I bring it up to around 3500 or 4000 RPM and then I shift, I feel a big THUD noise/feeling in the rear. Or if I am driving in first and clutch in fast at about 4000 RPM, again it almost feels like I got hit from behind.

Anybody else experience this?

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[Konamoth]

Perhaps just, MT-82 crunchiness. I get a similar experience in 1-2, 2-3—sometimes it seens to be a rougher engagement. Mine seems more from the center of the car, though. Maybe MY15-17 / MY18+ differences cause that.

Assuming nothing's glaringly wrong behind the transmission, being shaft, diff, axles etc., know that the MT-82 is a solid, albeit rough transmission. I've seen folks describe it as unrefined around here, and—yeah, that lines up, hah. It'll take a beating, but it won't shift like a Porsche.

 

[1MeanZ]

Is the thud less severe if you shift at a lower RPM? If you move the shift lever slower is the thud less severe?

 

[lazarus870]

Is the thud less severe if you shift at a lower RPM? If you move the shift lever slower is the thud less severe?

Yes. It is less severe or even not existant if I shift slower or lower rpm or clutch in slower.
But like, painfully slow to get it to go away.
Often times it makes it hard to get a smooth shift in the lower gears and is jerky.

 

[1MeanZ]

The clunk is caused by the rapid change in RPM of the main shaft and countershaft in the transmission. When you do the 1-2 upshift you mentioned above, the main shaft is spinning engine speed, when you pull the shifter into 2nd, the main shaft has to slow down several hundred RPM almost immediately, and that's the clunk you hear.

When you shift at a lower rpm and/or when you shift slower, the clunk goes away because you're reducing the amount of rpm drop the trans sees, and by shifting slower you're giving the trans more time to make that rpm change.

The clunk is normal, it's your driving style that is likely exaggerating the issue. A little more mechanical sympathy will go a long way towards extending the life of your trans and not having the clunk. Every time your trans clunks like that, the synchronizers are taking the hit, essentially shortening the life of your trans.

 

[lazarus870]

The clunk is caused by the rapid change in RPM of the main shaft and countershaft in the transmission. When you do the 1-2 upshift you mentioned above, the main shaft is spinning engine speed, when you pull the shifter into 2nd, the main shaft has to slow down several hundred RPM almost immediately, and that's the clunk you hear.

When you shift at a lower rpm and/or when you shift slower, the clunk goes away because you're reducing the amount of rpm drop the trans sees, and by shifting slower you're giving the trans more time to make that rpm change.

The clunk is normal, it's your driving style that is likely exaggerating the issue. A little more mechanical sympathy will go a long way towards extending the life of your trans and not having the clunk. Every time your trans clunks like that, the synchronizers are taking the hit, essentially shortening the life of your trans.

Sometimes though I will rev up to 4000 RPM in fast moving traffic, push the clutch in and hear that clunk and feel that thud from the rear. And it's not racing around, it's just keeping up with commuter traffic. With the 3.73's it revs up super quick. So I'm not exactly slamming it into gear. Or sometimes I am driving along and about to shift into second gear in traffic and the guy in front of me suddenly stops and I have to brake and clutch in and I hear that THUD.


So I'm not beating on the car, I'm just driving it normally and it's doing that.

Why is the THUD being heard and talked about more prevalently on these transmissions and not others? I've been driving exclusively manual cars since 2002.

 

[chesster51]

Sometimes though I will rev up to 4000 RPM in fast moving traffic, push the clutch in and hear that clunk and feel that thud from the rear. And it's not racing around, it's just keeping up with commuter traffic. With the 3.73's it revs up super quick. So I'm not exactly slamming it into gear. Or sometimes I am driving along and about to shift into second gear in traffic and the guy in front of me suddenly stops and I have to brake and clutch in and I hear that THUD.


So I'm not beating on the car, I'm just driving it normally and it's doing that.

Why is the THUD being heard and talked about more prevalently on these transmissions and not others? I've been driving exclusively manual cars since 2002.

Did you ever get this figured out? I have it too, but maybe not as bad as what you describe. I have the thud in the rear but also a "rattle" that comes from the large damper on the side of the trans. It rides on a shaft coming out of the trans and moves with every shift. It makes noise because because is wobbles on the shaft. I believe my thud in the rear is due to excessive gear lash in the dif. I've had it at the dealer for both issues. They acknowledged that the noises were present and then put a new manual car on the lift for comparison and it was identical to mine, same wobbly damper on the trans and same amount of driveshaft rotation before diff gears engaged. If you put your car on jackstands with trans in neutral you can turn the DS and easily recreate the thud. I don't like it but have come to accept it.

 

[lazarus870]

Did you ever get this figured out? I have it too, but maybe not as bad as what you describe. I have the thud in the rear but also a "rattle" that comes from the large damper on the side of the trans. It rides on a shaft coming out of the trans and moves with every shift. It makes noise because because is wobbles on the shaft. I believe my thud in the rear is due to excessive gear lash in the dif. I've had it at the dealer for both issues. They acknowledged that the noises were present and then put a new manual car on the lift for comparison and it was identical to mine, same wobbly damper on the trans and same amount of driveshaft rotation before diff gears engaged. If you put your car on jackstands with trans in neutral you can turn the DS and easily recreate the thud. I don't like it but have come to accept it.

Never had it figured out. The thud doesn't bother me anymore. But the sudden clunk when pushing the clutch in real fast is intermittent. Sometimes it comes on sometimes it doesn't. So long as it won't hurt the car, I can live with it I suppose lol

 

[Dkbyker33]

I get same thing I feel like a clunk when I shift gears passengers don’t notice it I can feel it from first second third only if cars cold it’s more smoother but from o read it’s normal I also have installs McLeod dual clutch amazing clutch btw gear shift soo smooth and amazing daily drive as well never missed a gear since installing it 2017 gt mustang driver

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