Bucking/Jerking STILL!!!!!!
 

ok so for those of you who have not heard me *****ing about this problem let me give you the symptoms:
car is a 1992 Camaro z28 with a new engine, 5 speed tranny, and new clutch, motor mounts, tranny mounts, tranny mount shim 1/8" thick. etc etc
-under steady throttle sudden let off of throttle it will jerk with a clunk, no matter what speed.
-if im just coasting like through a parking lot for example, and then give it gas it will shake foreward
--and sometimes after it shakes foreward, it picks up a rhythm and shakes back and forth until i give it more gas or put the clutch in.
-(i dont know if this one is related) during clutch engagement it will vibrate/shake excessively.

i have checked the universal joints and found nothing..... what could this be? i am absolutely stumped! ive tried everything.
tranny probs?
rear-end probs?
anything helps, wish me luck
thanks guys

RE: Bucking/Jerking STILL!!!!!!
 

maybe ya dunno how to drive stick? :Djust kiddin, but sounds to me like maybe the car has a lot of gear, and you are runnin a geared car in too high a gear at the tranny, run it in 4th instead of 5th an see what happens, when you turn superlow rpms, that stuff does happen, just a thought. also with solid mounts, it may be not absorbing vibration well enough

RE: Bucking/Jerking STILL!!!!!!
 

no im pretty sure its not that. i think it might be rear-end related. and the mounts are just direct replacement not solid.
thanks riceater

RE: Bucking/Jerking STILL!!!!!!
 

Just a wild guess, because it is hard to diagnose a problem long ditance. Flywheel or pressure plate bolts loose?

RE: Bucking/Jerking STILL!!!!!!
 

i dont know if it can be that because ive had the clutch replaced and the flywheel turned twice!!! im absolutely stumped

RE: Bucking/Jerking STILL!!!!!!
 

New engine....Can't be certain, I can check. If it's a new motor with a 5 speed. Was the motor a donor, or a rebuild of the existing? I ask because you could have the harmonics fubared if you put a automatic motor with a manual drivetrain. Some chev's you'll need a different harmonic balancer because of it being hooked to a manual trans.

It'll also eat mains like crazy if it's the wrong set up.

Is it a gear specific shake?

Warm?Cold? any difference?

Original drive train?

RE: Bucking/Jerking STILL!!!!!!
 

[&:] id maybe check the rearend for play. if a lot of wear has produced excessive backlash i could see some of your symptoms coming from this(clunk when letting off throttle). sounds like you may have multiple problems here including a pretty good shudder coming from the clutch and maybe some computer/drivability problems. as for harmonic balancers being the cause i really, really doubt it as the symptoms arent harmonic and to the best of my knowledge they did come in a couple different sizes for the 350, others being specific to engine size, and the balancer for the 400 different than the rest but NONE were specific to trans type. as pete suggested maybe check flywheel and pressure plate bolts also what kind of clutch factory replacement or aftermarket racey race unit?? what kind of shape was the trans in when you installed it, used,tight, was it checked?? has the engine been checked for codes?? when was the last time you cleaned the idle air control valve?? kurt

RE: Bucking/Jerking STILL!!!!!!
 

At first look I would think the 'picked up a rythm and back and forth shaking untill you give it gas or puch in the clutch thing' is operator head space and timing, but then almost everything you mentioned seems to be from the flywheel - back. The clutch is working or it would still shake back and forth. How does the fluid in the tranny look? I am thinking the tranny is the culprit.

RE: Bucking/Jerking STILL!!!!!!
 

Good descriptions guys, thanks for the reminder on 350 harmonics. I was thinking BB.

Besides that. When you swapped motors you did remember to put the pilot bushing back in the rear of the crank right?

Not "feeling" your vibration it's tough to tell how extreme your talking. A little front shaft end play with no bushing could cause a vibration. Clunk, doubt it, but a slight vibration that could cause other things to get worse.