hi my english is bad but all do my best,between 2800 rpm to 3300 i ave thise crazy vibration in the stick shift on avray gear. i change the drive shaft,nothing same thing,brand new clutch,same thing,i just blow up my m21,change the transmition my self to a new m21,same thing whit that crazy vibration, can some one help me


yesterday i drove for about 3 hour at 2800 rpm cost me 120$ in gas at 1.46 a litter,yaaaaaah i love my car need a 5 speed

 

When you changed the transmission did you ever remove and check the flywheel?

What is the condition of the balancer on the front of the engine?

 

no i dint check the flyw,but am not a+ mecano but all do my best,what should i check on the flywheel? in what is the balancer on the front engine?thanks a lot for your time in help

 

The 'harmonic balancer' is the lower pulley/weighted damper on the front of your engine. It has some elastomer (elastic) material built into it which allows it to absorb natural engine vibrations (harmonics) which occur due to the combustion cycle. If your vibration happens at specific frequencies as you rev the engine, regardless of which gear you are in, then the balancer/damper may be your problem. If, however, the vibration starts at some specific engine RPM and continues to get worse as you increase RPM, then some component on [or in] the engine is not balanced properly. The prior suggestion was that it could be the flywheel. That could be true, but most likely because you may have changed the indexing of that flywheel from its original position (not oriented exactly the same as it was when you removed it to change the transmission). There are lots of things which could cause your vibration, but it is likely something that you removed/changed during your transmission repair, like the flywheel, clutch disc, pressure plate, etc. It could also be a damaged/worn U-joint on the driveshaft, or a lot of other rotating mechanical devices attached to your engine.

 

Good point, there should be an alignment pin in the flange of the crank to properly index the flywheel. If you don't have that pin there will be a hole that can line up on both the crank flange and the flywheel.

 

I agree with the others as a possible source of your vibration. Don't rule out your exhaust. I had been chasing an RPM related vibration in my 61 for about a year. It was the exhaust ratlling against the frame. Different setup with the C3 but check your exhaust clearances. Good luck.

 

thanks a lot for your time, i add the same problem beford the transmition change,past 3600 rpm it stope in run very nice all the way up t0 5800,all 6 U-joint are brand new, 2 monht ago i add the all engine rebuilt by gmc garage cost me 4000$ but there dint look like thy know a lot about c3 but my 454 rune very nice,the balancer if i buy a new one in put it my self, can i see for my self if it that or chould i ave the gmc guy check it? the feel of puting avray screw in it is what am looking for thanks for your time

 

thanks it those touch the frame,on boht side of the crosse member,thy touch it inside the hole,but the gm guy weld it ,if i disconect it frome my header,in make a qwick drive aroud, you think it be good to know if it that ? thanks

 

Hello,

If you put the car in neutral and rev the engine to 28-3100 rpm do you still have the vibration?? If not then this eliminates the harmonic balancer,flywheel, clutch and pressure plate. Next I would inspect all six U-joints and ensure that they are all seated correctly, and bolts are tight. (read the "Wrong U-joint" post abit further down from yours).Next check your transmission mount to ensure its not split or loose. Finally I would suspect your transmission/ driveshaft/ rearend/ u-joint angles. To confirm this place a 1/8 " spacer between the transmission and the trans mount ( this alters the u-joint angles). By doing this the vibration will go away, or move to a different rpm band.
Let us know what happens!!

 

A key issue here is to separate engine vibration from drivetrain vibration. What happens when you rev it in neutral?

 

Actually, revving it up to 3000+ rpm in neutral and NOT having the vibration would eliminate the engine and anything directly mounted to the engine (as mentioned above). The is a simple and "must do" test to help you isolate the cause.

 

i went to try it on reverse crazy backing up at 3000 rpm,no vibration,i check all the u joint all good,i just went in rev it up to 3000 same vibration,in am not in gear,am getting ready to put that 1/8 plate to see but all wait your reply thanks a lot

i got the same vibration on neutral,it feel like it coming frome the engine,my exhaust are touching the cross member???

 

If your exhaust is touching the crossmember that is exactly the situation I was dealing with and I felt it right through the shifter. Exhaust hitting the frame will vibrate right through everything.

 

hi am missing completly the front exhaust pipe hangers,as thy hang hard on the crossmember, i just order it frome zip

am sure that what it was after the rev on neutral,all let you know wene i get the part. thanks a lot fot your time

 

While reving in neutral watch the fan blade and see if it sets up a vibration.Like a wobble.

 

hi i ave a be cool dual fan on it, thanks

 

Since it has the vibration in neutral, as well as in gear, the problem has to be somewhere in or hooked to the engine. As you were working on the tranny hook up/clutch area, my priority of items is:
1. flywheel misindexed (the flywheel was balanced as a rotating assembly with the crank, etc. and should have been marked when you removed it...so you could assemble it hole-for-hole the same way. Since it has 6 bolts, you could have lined it up with any of them.)
2. flywheel got cocked on its pilot and is not all the way seated on the drive hub.
3. the pressure plate/clutch disc assembly is not centered or one [or more] of the attachment bolts did not get fully torqued.
I'm sure others with have additional suggestions. Hope you find it and it's not a big job to fix.

 

Did that BOO BOO on a 71 Camaro I had with a 400 in it.

 

ok i take off the exaust just 5 minute ago rev it frome 2000 to 3500 no vibration at all just a bit but normal for a big block i guess i found it

thinks a lot pepole

 

Hey, somebody found the "EASY" button!! {and I thought it only worked at Staples..}