I have owned my car for 6 years, 1972 Dodge Charger with rebuilt 1990 360 motor. 9:1 stock or small upgrade cam. Davis HEI Ignition, Holley street avenger carb. Stiff suspension and ride with heavier springs, shocks, torsion and sway bars, 18" wheels, 45 series tires. Driven 4X/week on street only, rough roads here in urban L.A. B&M Flexplate, Mopar performance 145K torque converter with neutral balance (no weight(s)). When torque converter was installed 5 years ago the shop had to knock off the weight to make converter neutral balance as B&M Flexplate is already balanced. Car ran smooth and strong for many years. 1 year ago I noticed a little vibration upon acceleration. Got progressively worse over the last year. No one else that anything unusual but I knew better. Got progressively worse until others noticed vibration and then clunking over bumps. Sure enough, tranny mount was bad but that stopped clunking, not vibration. Rebuilt carb, new plugs, verified timing, verified spark plug wire order. Car runs really strong but vibration still there. 18" vacuum at idle and needle rock solid so I cannot believe it is a tuning issue. I replaced harmonic damper with Summit Racing damper #163318 for external balance 360. My old damper looks exactly like Mopar Performance P5007301. If anything vibration may be worse. Then replaced motor mounts. Still no change. Vibration is so bad now I only drive car to take it to get opinions from expert mechanics. For sure it is engine/balancing/torque converter as vibration is there when car in park or neutral or when it is driven, hot or cold. Exact same smyptoms as Kielbasa's original vibration post only mine have developed over time. Dash, steering wheel, and floor pan shake at anything above idle, sort of smooths out on hiway but turns into a droning vibration. Front of engine and rear of car don't seem to have vibration, it is centered in rear of engine/front of tranny. Help!!! Don't know what to replace or check next. Can a torque converter go out of balance from neutral? Thinking of rebuilding original damper but now I am getting into replacing my new replacement parts...

Also TTi headers and new exhaust in 2004. Exhaust till looks good although mufflers have a few pinholes, no clearance issues.

sounds like my dad's cars problems. he's rebuilding his motor. that after we've messed w/ the transmission 20 times (in and out) in the past 2-3 years

could it b an accessory that is belt driven try removing the belts and see if it goes away that has beat up many of techs for vibration including me. some waterpump pulleys are close to crankshaft ratio and can be misinterpeted as a crank speed issue. i would at least try that before i yank the engine and dive in too deep. you have to look at everything that spins start simple.

Well, it was worth a shot. I did pull off all accessory belts and ran her in park and up and down the block. No change.

18X8 front wheels with low profile tires and no power steering in a B Body - BIG arm muscles!!!

First I would get rid of the Summit RACE Damper.
360's are very different in balance than 273,318
and 340's (THEY ARE EXTERNALLY BALANCED)
Stick to the Mopar Performance Damper that is
compatible with the offset balance (external) 360.
Recheck the specs on the B&M flexplate, (weight
INDEXED CORRECTLY!) and 145K torque converter.
Actually, the converter should have never had the
weight removed. It really should have been checked
from the beginning for the proper application (food for thought). Last, I would look at the trans input shaft for excessive play (again food for thought).

Also, with the 145K torque converter, it's offered
for both the 727 and 904. You didn't say which
one you have, or I overlooked it in your post.
The slightly rarer A-999 transmission is the
heavy-duty version of the A-904, so you have a
two basic versions of this type of converter, with
the other choice being for the A-727 transmission,
which is more common piece. Check on that weight
removal situation of that 145k unit. It could be
the direction you need to go for your problem.

My transmission is a 904. For those reading post please realize engine was perfectly balanced and vibration free for many years with stock external balance damper, B&M external balance flexplate, 145K torque converter (for 360) with weight knocked off. Converter needs to be neutral balance as B&M flexplate does the balancing for the backside of engine unlike stock flexplate. The Summit damper I bought WAS for a external balance 360 and is counterweighted in a similar position as the stock damper I removed. My vibration problem developed steadily over the last year, I believe due to the bad tranny mount.

Maybe when tranny was knocking around mount metal to metal flexplate or converter got out of balance?

Any other areas to look at?

The last sentence of your post should give you
a clue. I do understand about the "neutral
balance" converter also. But, something is not
"right" in that converter/flexplate area. I would
check thoroughly for bends, cracks and hole
elongation in the mounting areas of the converter.
It may be possible that the stator/turbine combo
inside might be slightly out of balance. I don't
know how you drive but I would check the mounting
bolts on the transmission and crossmember just for
an extra shot of good measure. While you are under
the car, it also would not hurt to check for the
exhaust pipe clearance to any frame/torsion bar/
crossmember. Sometimes a loose pipe could vibrate
thru the cab without excessive noise and drive you nuts! More food for thought. Good luck.

Are the dowels in the back of the block? The trans may be shifting on the block.

Get rid of pin-holed mufflers while you're at it. Dyno-Max Turbos have no drone behind my TTI's Good luck.

worn out timing set, bad bearing in the water pump?

Any luck yet with the vibration problem ?

Loose converter bolts, worn bushings on input shaft of transmission, bad converter, broken crankshaft. One thing you might consider, though it's a bit drastic, install the proper 130 tooth flywheel in place of the flexplate/torque converter combo and see if the vibration goes away. At least then you'll know if it's transmission or engine.

Have you ever heard of knocking the weights off of the converter for the B&M Flexplate? I always
used the standard flexplate for mild applications
(5500-below).

Check your bolts on your trans to engine ,had a chevy one time ,drove me crazy ,the bellhousing bolts were loose ,did the exact same thing ,drove me crazy

Great tech help! Thanks man! Just relay it to
Hazwoy for his 72' Charger.

Eureka and thank you all for your answers and expertise!!!

PLEASE SEE MY UPDATED POST 1/12/10- The mount did NOT contribute to vibration. Only make it worse if you already have a problem.

I found and solved most of the vibration problem by ditching my brand new heavy duty Prothane polyurethane transmission mount for a cheap Auto Zone made in China/stock rubber one. It was the only option I could try with out a lot of time and effort. Unbelievable the difference!!! The Prothane metal looks twice as thick and well constructed with beefy round poly bushing. My original mount looked looked like stock mount but no sleeve or tube to encase the bushing between the vertical supports. It did have a poly bushing in it that went bad and when I ordered a replacement I figured why not upgrade. Now with the new stock style mount I have a slight shaking vibration at about 1800 rpm (still in the same area- firewall/steering wheel/gas pedal) but car is totally drivable, just slightly annoying. I plan next to try a stock style mount with new poly bushing to see if that is better. Anyone have a spare old original mount they don't need?

The droning is still there from about 60-85 mph but my intuition tells me that is my pinholed mufflers

My original mount looked looked like stock mount but no sleeve or tube to encase the bushing between the vertical supports. It did have a poly bushing in it that went bad and when I ordered a replacement I figured why not upgrade. AND I threw the old mount out when I put in the Prothane mount.

Last question- anyone else have original stock mount without that sleeve/tube to support the bushing? Maybe whoever put in the aftermarket bushing removed it? Bushing did seem to fit many years ago...

Prothane #1603-BL mount that did not help my vibration issue

Glad to be one of the many members to help. The
"droning" noise that you hear at 60-85 mph, might
be a simple exhaust issue. Question: Do you
have an exhaust crossover pipe somewhere between the header collector and 36" before the
inlet of the mufflers. Mopars seem to run better
and bit quieter with this pipe in place. The car,
while not an "all-out racer", needs all the
low and midrange torque it can get to run really
well on the street. This may help, along with
better flowing mufflers.

ALL RIGHT!! FINALLY back on the road. After weeks of diagnosing and not driving my daily driver I am back on the road. Even tho it didn't make sense I REBUILT THE ORIGINAL DAMPER and THE VIBRATION IS GONE!!! Thank you, http://www.damperdoctor.com/ I don't know why the Summit replacement damper didn't work, it was proper application (1971-1992 360 external balance) and looked to be counterweighted correctly. To Summit's credit they did refund money 60 days after purchase and use of damper.

I do have a bit of droning left around 2700 rpm but I am sure it is my old mufflers and exhaust. I had 2 1/4" exhaust with Magnaflow mufflers, no droning when first installed. I took out the crossover with no change and just cut off the tailpipes just after the rear axle and removed crossover. Exhaust a little louder and droning reduced. I am going to replace exhaust system from headers back but have to repair a small leak in tank first.