A833 Vibration Issue

-

pa karp

Well-Known Member
Joined
May 16, 2013
Messages
232
Reaction score
20
Location
Ft Pierre
I have been chasing two vibrations in my 340 1969 'Cuda. I got the drive shaft issue taken care of, new drive shaft from a supplier that knew what they were doing.

There is a 2nd issue. I have a vibration at 3000 rpm, aproximately 65 mph. When I kick in the clutch, let the engine go to idle, or shut the engine off, and shift the trans into neutral the vibration goes away. No vibration what so ever, clutch in or out.

I have checked the flywheel and dampner, both are neutral balance because of the forged crank. The engine has been balanced by my reputable engine builder.

Where this gets really interesting, with the engine at idle or shut off, when i depress the clutch and shift the trans into 4th the vibration returns! I do not engage the clutch. When I shift the trans into neutral, the vibration stays, whether the engine is at idle or shut off. I repeat the process, vibration disappears as soon as I shift into neutral. But if I shift back into 4th, clutch depressed, the vibration is back.

What should I be looking for here? Is this a possible bushing issue in the trans tail shaft?

Thanks

Curt Rees
 
I would check for a worn tailshaft on the front of the driveshaft. hat was what was causing my vibration. It had worn internally on the splined portion. Everything else checked out on the driveshaft. It was all new, except for the tail shaft.
 
We have determined the vibration issue is not transmission related. The transmission is coming out and we are going to take a hard look at the clutch disc, pressure plate and flywheel.

The flywheel is a neutral balanced unit. The motor was blueprinted and balanced when it was put together. Not thinking, I did not send the flywheel with the motor to be checked when the engine was built. That very well could be my problem.

I did send the harmonic balancer. It is the correct unit and is OK.

Curt Rees
 
Have them balance the pressure plate also on your flywheel. Paint a stripe on the pressure plate and flywheel so you can reassemble them the same every time.
 
Thank you! Good idea. This has been a learning expierence for me.

Curt Rees
 
I just talked to my engine builder. They can balance the pressure plate to the flywheel.

That is what we are going to do. Lesson learned!

Curt Rees
 
my guess would be the tranny needs rebuilt

if it was the pressure plate/flywheel/etc it would still do it in neutral. pressing in the clutch pedal might make it go away.

but yours does it in 4th at highway speed, then goes away when you push in the clutch and shift to neutral. almost would bet it's the input bearing.

there are some trans experts on here wait for them to chime in.

also check the runout on the bell housing like fklskv recommended
 
If you're running a scattershield or any bellhousing really, you need to be check to be certain the rear transmission mounting face is parallel with the flywheel/crank flange. The back mounting surface of the block may not be perfectly square either. I have to run two .020 shims and two .010 shims to get mine parallel.

I also have to run the offset dowels to get it lined up with the crank shaft centerline, and they were not off by just a little. The quality control at Lakewood leaves a lot to be desired.

There are two steps to this process and the first is often forgotten or simply not done. It does affect shift quality and associated part life.
 
Curt, thanks for sharing your and thanks to FABO for weighing in. These are lessons that everyone can benefit from. Neutral balance motors need neutral balance harmonic dampner and neutral balance flywheel and clutch cover. "The simpler you try to make things, the more complicated it becomes." (Bill 'Grumpy' Jenkins) Tom Damon
 
I have the stock bell housing. I drove the car several more times coasting from 70 mph down. In neutral. motor idling, motor off. clutch in, in neutral and in gear. As long as the trans was disengaged, the vibration went away. The vibration is there at 2000 rpm and up even with car sitting still.

We had the trans completely apart. The only things needed, were the tail shaft bushing, gaskets and seals.

The vibration is weird, it pulses, even sitting still! More rpm, the worse it is.

Curt Rees
 
did you check the runout on the mainshaft while it was apart. Meaning did you check to see if it was bent. very common on a mopar 4 speed if it was behind a motor that blew/locked up. You can have them straightened by almost any good machine shop. most common problem is mystery vibration and cracked synchros.
 
I have the stock bell housing. I drove the car several more times coasting from 70 mph down. In neutral. motor idling, motor off. clutch in, in neutral and in gear. As long as the trans was disengaged, the vibration went away. The vibration is there at 2000 rpm and up even with car sitting still.

We had the trans completely apart. The only things needed, were the tail shaft bushing, gaskets and seals.

The vibration is weird, it pulses, even sitting still! More rpm, the worse it is.

Curt Rees

I'm confused. You are basically saying that

with the car stopped

the trans in neutral or the clutch pressed in........

the vibration is still there "from the engine" depending on RPM?

If so, this pretty much eliminates the transmission. There is some chance it could be clutch related

IF this is so, what I'd be tempted to do:

CONFIRM this is so with car stopped

With the engine cold, CONFIRM the vibration, then pull the belts and recheck with no belts

If no change, pull the clutch linkage, and pull the gearbox. Get the fork and T/O out of the way

If it still vibrates, pull out the clutch assy.

Obviously if it STILL vibrates, it's somewhere in the engine

THAT could be some things

Some sort of miss or low cylinder, etc

wrong balancer

wrong or modified flywheel.

Something 'lyin' about the rotating mass of the engine.......seriously different pistons or rods, etc.

Or something actually wrong....bad bearing, etc

Consider a CRITICAL cylinder balance, cylinder leakdown, vacuum gauge diagnostics, and even suspect ignition problems, bad plug wire, etc.
 
It vibrates with the car stopped, clutch in or out, trans in neutral or in gear, clutched depressed. The vibration comes at 2500 rpm and will pulse.

Our plan is to do what is being suggested. Step by step.

Our suspicion is in the clutch area. Very possible the flywheel, even though it is a neutral balance.

This build has been interesting, lots of issues have popped up, some small, some major. But I am able to drive the car. Thanks for the responses, I learned long ago to ask questions from the experts if your not sure on project. It makes progress much easier to acomplish!

Curt Rees
 
When you coast down, clutch in motor idling or off it goes away. So try coasting down clutch in, and keep the engine RPMS at 2500. If the vibration is there then, it's in the engine or something connected to it.
 
I did the 2500 rpm test tonight. Clutch in trans in neutral and then trans in gear, clutch out trans in neutral. In each case no vibration at idle, once I increased the rpm to 2500 the vibration started.

My conclusion is the vibration is pressure plate forward. Next step, pull the trans and start checking.

Curt Rees
 
Yup. It's all bellhousing / forward. You have? pulled the belts?

If so, next thing I'd do is yank the trans and clutch, and run it with just the flywheel. Test it thuroughly in that mode and recheck with belts off.

Take a GOOD look at engine mounts. Probably a good idea after pulling the clutch to re-install the gearbox to properly support the engine in it's "normal" mounts
 
I have only the alternator belt, no air of power steering. I will pull the alternator belt and try it.

The engine has the factory mounts. They looked good when I put the motor in.

The transmission mount is factory. I do have a new one that will put in when we re-install the transmission.

Process of elimination!

Curt Rees
 
Pay attention to what 67Dart273 tells you!. I pulled the belt off the water the water pump and, wala, my vibration went away! In examining the pulley and fan, the pulley was bent. My mechanic had not seen such a thing and he is a long time MOPAR guru.

I did pull the trans, pressure plate, clutch disc and flywheel anyway, since I had a severe oil pan leak that could not be repaired until they were out of the way. Since it was apart, I decided to put in a SFI billet flywheel and a heavy Ram clutch assembly, even though the car will only see limited strip duty. I now have a good stock spare flywheel and clutch assembly if I need it.

Curt Rees:burnout:
 
I can tell you what it was in my similar situation. I had a bad vibration problem while driving and sitting at idle. It was bad at idle where the dash and the whole front end rattled. I checked everything and my problem ended up being a bad pressure plate. My set up was a 340 4 speed. So if you have access to a wheel balancer, spin your flywheel, then spin with pressure plate bolted up. You have to be able to mount it safely to the balancer. When I did this my flywheel spun zero. It was all over the place with the pressure plate bolted up. I was running a stock replacement pressure plate and if I remember correctly they weren't too expensive at the time. The pressure plat has weights on it too and needs to be properly balanced. In my case I think it was a bad reman possibly.
 
hi, what shape is your pilot bushing in? if it's bad , it will cause vibration in clutch. need to measure dia and input shaft dia, to see difference. I had same problem, the bushing was worn out. replaced it, no vibrations. just food for thought.
 
Vibration is gone! After more money, oh well.

I was able get to a drag strip, KRP in NE since Oahe had closed for the season. I made 4 passes in the 14's, the best at 14:74. Since KRP is at 2100 feet, with the factor that would be a 14:50.

That was my goal all year. 14:50's is what it ran in 1969.:burnout:

Curt Rees
 
-
Back
Top