Engine and Flywheel Balance

[BIGBAND39]

I just came back from my mechanic after telling him about what I thought was a driveline vibration.  He informed me that the vibration also occurs when the vehicle is in neutral; that it can be felt in the wheel.  He asked me what work I have had done since my purchase and I explained the my rear main seal was replaced.  He had asked if the last mechanic had indexed the flywheel and "flywheel cover" and I told him that I didn't remember him doing so.    Can anyone explain in layman's terms exactly what indexing and balancing the flywheel entails?  I could imagine that if it was out of balance, it would cause a vibration.  Also, the engine was rebuilt years before I bought the car.  I would guess that a professional shop doing the job would also balance the engine during the rebuild.  Is this engine internally or externally balanced?  Thanks for any insight.  As a shade tree mechanic, I've never come across this sort of stuff.

[Don Coatney]

The flywheel be it 4-6-or 8 bolt will only bolt on correctly one way as the holes are not symmetrical. All engine re-builders should know this and most mark the flywheel and crankshaft when dissembling the engine.  Failure to do so could possibly cause an out of balance issue.

[Dartgame]

some engines are internally balanced meaning the crankshaft is neutrally balanced and the rods and pistons are balanced to match the crank. The  flywheel in such an  engine will also be neutral balanced meaning the flywheel doesn't require weights or special orientation. As far as I know the mopar flat heads are internally balanced engines so no there does not need to be a pattern for orientation of the flywheel.

[55 Fargo]

As mentioned above, the flywheel goes on only 1 way, and do not think it could be installed otherwise.

I have removed and installed a few of these, they only go back on 1 way, as per the asymmetrical pattern.

I don't know, not sure this mechanic, is correct or full of it...

[desoto1939]

on your 39 dodge just like my 39 Desoto you have a harmonic balancer and lower pulley or otherwise known as a vibration dampener.  This might have good bad and then you get vibrations when the car engine is running.  This happened to me when the rear and front motor mounts were replaced and we picked up the vibration. Upon putting on a new harmonic balance the issue was resolved.

Check the other posting in regarding to the other gentleman that has a 39 Dodge and I listed the various cars and years that use the same harmonic balancer. Have your mechanic check the balancer to see if there is any sort of wobble in the lower pulley.

Rich Hartung

Desoto1939@aol.com

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[BIGBAND39]

Could one simply unbolt the flywheel from the crank and rotate it until the vibrations go away, Don?  After talking to the mechanic he did say that if the flywheel only bolts on one way that it's likely not the culprit.   I sat in the car today and, reving at about 1500rpm, she has a very noticeable vibration.  He tells me that he thinks it's in the balance of motor.  He also said it wasn't likely the harmonic balancer due to my idle being so smooth. He said the rebuilt would be at a cost of $200+ without labor.  Funny enough, I drove the car today and the most noticeable vibes hit when I'm driving 50+ mph.  If I take the engage the car, the vibes persist.  If this was a engine balance issue, wouldn't the vibes go away when the clutch is in allowing the engine to wind down?

Edited April 28, 2017 by BIGBAND39

[BIGBAND39]

After talking to the mechanic he did say that if the flywheel only bolts on one way that it's likely not the culprit.   I sat in the car today and, at about 1500rpm, she has a very noticeable vibration.  He tells me that he thinks it's in the motor.  He also mentioned having the harmonic balancer rebuilt at a cost of $200+ without labor.  Funny enough, I drove the car today and the most noticeable vibes hit when I'm driving 50+ mph.  If I take the engage the car, the vibes persist.  If this was a engine balance issue, wouldn't the vibes go away when the clutch is in allowing the engine to wind down?

[BIGBAND39]

Does the 218 of this era have a harmonic balancer with an option for the crankshaft vibration dampener?

[desoto1939]

Update on number and cars: The 39 Dodge uses a Harmonic balancer and this information was taken from my TriState MoPar Distributer catalog. There is another post with a owner that has a 39 Dodge and has a similar issue so this is the information that I sent to him

According to My Tristate  MoPar distrubtor catalog

Ply 42-50 Vibration Dampener with Pulley  869431

Dodge 37-50 dampener with pulley   869431

Desoto 38-42  but not Fluid drive 869431

Chrylser 41-50  With Fluid Drive  869431

also check your parts book and I assume that you have a 39 Dodge parts book as a reference.

So my thinking is that there should be some available. Hope this helps. This is why you need the supportive catalogs.

 

I also verified in my 39 Dodge Parts manual that there is a  Impulse Neutralizer ( vibration dampeners.) The 1939 part number is 677995 but also looked in the my 36-42 Dodge Master parts catalog and the number is the same as the above 869431 which covers more years. Hope this helps.

Rich Hartung

Desoto1939@aol.com

[BIGBAND39]

I do have a parts manual!  I just hadn't made my way home yet to reference.  So, comparing the two, the harmonic balancer is a crankshaft vibration dampener.  Looking at that post and others I was confused that some 218s came with dampaner and others didn't.   This is a non-Fluid Drive three speed set up.

[JerseyHarold]

Are all the flywheel bolts properly tightened?  A loose one can cause a vibration like you're experiencing.

[BIGBAND39]

I was under the car with my mechanic when it was pulled apart.  I wasn't there when it was reassembled.  I appreciate the suggestion but, although he may not be 100% with older vehicles, he is very thorough.   I think he would have tightened everything up.  If they should be tightened to a specific torque spec, that's a different story.  I'm not sure if that would make a difference.

[wayfarer]

How long have you been driving the car? When did you first notice the issue? I'd be looking at all of the engine mounts/rubber insulators.

As to the flywheel, the amount of torque only affects balance if it is inadequate and a bolt/nut gets loose/falls out....not a likely scenario.

As stated, the flywheel only goes on one way due to one bolt having been moved in the pattern, so I'd be looking at the pressure plate bolts to insure that they are correct as this could allow for a very slight misalignment and subsequent vibration. This is not real high on my 'likely-suspects' list however.

[BIGBAND39]

I always had a vibration but, to be honest, I would expect that out of a 75 year old car doing 55.  The vibration definitely became more noticeable after the rear main seal was done.  I personally thought it was a driveshaft issue possibly from it not being properly indexed.  This new mechanic is dead set on it being engine related.  It still doesn't seem to make sense as, when I push in the clutch and wind the motor down I still get vibes at high speeds. 

[desoto1939]

Has the mechanic checked the vibration dampener this affects the internal vibration of the engine. Also as someone stated above check the three motor mounts they mabe be shot after 75 years. The front motor mount is what the engine rests on just below the water pump.  Please check these and also the trans upper and lower motor mounts. They could be so hard rubber that they are not absorbing any of the engine vibrations.  If you have not chnaged these then I would advise doing this first since it is and easy job for a mechanic to do.  Get fresh rubber not NOS stock becasue the rubber gets hard over the years.  i replace all my motos mounts when we had the clutch done.

Have the mechanic check the driveshaft to see if there is any  slop inthe ujoints.  I have extra Detroit U joints with the internals and the housings and the leather covers if needed.  I also have the miller tool to push out the pin and set the pin in the proper depth on the ball end of the drive shaft. Contact me if you need any of these items.  These are NOS u-joints american made not chinese crap.

 

Rich Hartung

Desoto1939@aol.com