BRZ: trouble starting from a stop (car shakes)

Hey all,

Recently, my 2016 brz has developed a troubling habit of shuddering (juddering, jittering?? - one of these verbs should work) from a stop. Basically, under light/standard throttle, I'll get a lot of vibration when letting clutch out and pulling away from a stop. It typically isn't super smooth, and the gear stick will vibrate. I thought I suddenly forgot how to drive manual, but the performance shop I took it to had the same issues. 

I asked them to check the transmission mounts, but those seemed fine. Ditto to the motor mounts. Anything else you all can think of checking? The clutch, pressure plate, and throwout bearing were all replaced in early 2020, and the clutch seems fine in all other circumstances (picks up revs fine on downshifts, doesn't slip, etc). I'm a bit stumped on this one. Thanks in advance for any help :)

Cheers,
Christopher 

Damaged flywheel or pressure plate is my guess.. Could be warped, cracked or hot spotted. 

One thing that I've heard with the TOB failure in these things is that if you drive it for any length of time with the TOB seized up it will wear a spot into the trans input shaft, which then prevents the clutch from sliding smoothly on it, leading to funky issues with the clutch takeup. Unfortunately, the only fix is a new input shaft.

I had to limp mine about 15 miles home last spring when the TOB suddenly went out on me. Even using the clutch absolutely as little as possible, there was still slight but noticeable wear on the input shaft. Hasn't presented any issues for me, but I'm really glad I didn't push it any farther than I did. 

Does it only shake as the clutch is engaging?  Needs a clutch.

Does it shake after the clutch is completly engaged?  Check your driveshaft joints.

In reply to Streetwiseguy :

Beat me to it.

Not sure of how many miles you have on it, but I experienced a similar clutch issue that fortunately turned out to be 3 loose spark plugs our '06 Nissan Frontier (purchase used in '17 or so). Out of the blue it would shudder a just a bit while letting the clutch out. Then it started to idle a bit rough shortly after this issue appeared. Service records indicated that it was last tuned (at a Nissan dealership) the year before we got. But I pulled plugs anyway only to find 3 that were very loose. The shudder was gone after I replaced the plugs.