Engine/drivetrain vibration?

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"If it was internally balanced like an early 340 then a neutral balance 340 vibration damper would fix the problem. No weights are on the converter now so nothing would need to be done there. This is all assuming it was internally balanced like an early 340 which I am not sure they did?"

This sounds like a logical solution, however, wouldn't you still need to perform some kind if balancing on the drivetrain -- even if you now have a neutrally balanced engine, torque converter and harmonic balancer? This approach might improve the vibration, but I still don't see how the drivetrain would be fully in balance. Making I'm making this too difficult.

Thanks
 
Also, in re-reading other notes my guess would be that if there is an unbalanced situation with a cast crank/damper/tc combo you should be able to feel it without driving the car, because the tc is part of the rotating assembly... So, if you were in park and brought the rpms up you should feel the vibrations if it's out of balance... In my previous note, the weights have to be in the right placement, not just any weight anywhere... This is only advice, don't try this at home, we are not experts!... Hope your on the right trail....
 
67Dart340,

Yes, you can feel the vibration when the car is in park and you rev it up. I believe that eliminates the driveshaft as a suspect.
 
Good, so it looks like your on the right track... Find out exactly what the people did that worked on the motor, and do you have the original tc to look at the weights and position... After this it's putting the puzzle back together...
 
Is there a degree of angle at the driveshaft going into the tailshaft housing, or is it straight from driveshaft to housing?

If it's straight, it will most likely cause a vibration.........there should be a little downward angle on the driveshaft. 8)
 
DartSportDude said:
"If it was internally balanced like an early 340 then a neutral balance 340 vibration damper would fix the problem. No weights are on the converter now so nothing would need to be done there. This is all assuming it was internally balanced like an early 340 which I am not sure they did?"

This sounds like a logical solution, however, wouldn't you still need to perform some kind if balancing on the drivetrain -- even if you now have a neutrally balanced engine, torque converter and harmonic balancer? This approach might improve the vibration, but I still don't see how the drivetrain would be fully in balance. Making I'm making this too difficult.

Thanks
Click to expand...

On an early 340 which is internally balanced the vibration damper is neutral and so is the torque converter. Therefore they don't need to be balanced. I did take my new vibration damper to the shop and have them check it to make sure it was truly neutral balance though. But in general, no, an internally balanced engine does not need its torque converter and vibration damper balanced but its not a bad idea to have them checked to make sure they are truly neutral.

Also, in your post above, you talked about going with a neutral balance damper and B&M flex plate. The flex plate is only needed if its externally balanced. Do not change the flex plate until you determine how the engine was balanced.

Did you go with lighter aftermarket pistons? If so what did they weigh? You can find out if you get the part number and look them up. If they were much lighter then the originals they might have been able to balance it internally with out adding mallory to the crank. If the pistons weighed close to the originals mallory would have to had been added to the crank to internally balance the engine. If they had to add mallory to the crank that is not cheap to do and you would see that in the bill. I would think they would remember that also because its a bit of work. So finding out what pistons were used and how much they weighed would really help in figuring out what they did.

Did they take the original damper into account or just assume it was neutral balance and set it aside when they balanced it? I don't think it would balance correctly with an external balance damper and no weights on the rear to simulate the external balance torque converter (or flex plate).
 
You guys probably think I'm some kind of a nut ball with this continuing saga! Frankly, I'm about ready to kill all of the parties involved with this rebuild. Anyway, here's the latest...

- My repair guy just called. He spent an hour in the back area of the machine shop, quizzing their guys about this job. It appears there is NO record of this engine having been balanced as part of the rebuild (even though the final receipt lists "balancing" under the work performed). The machine shop has no notes or records concerning this job, and the guy who performs most of their balancing has no recollection of balancing my engine. Thus, my repair guy now believes the engine was NOT balanced as part of the rebuild

- The shop that performed the original engine r&r on this job has confirmed that they did NOT send the torque converter to the machine shop when the engine went in for the rebuild

- Based on this scenario, it is very possible that my '73 340 was not rebalanced to a neutral balance, ala an earlier forged crank 340.

- The next step? My repair guy wants to pull the torque converter and send it to his tranny shop to have it evaluated. If it appears the torque converter is defective, then we might have our culprit. At that point, we would just installed the correct, balanced TC for the '73 motor and hopefully that will correct the vibration.

- My repair guy is also going to confirm if the existing balancer is correct for the '73 engine. We need to eliminate that variable, too.

The problem with all of this is there are no clear records on what was done at the machine shop. That means we're just fishing for a solution. Frankly, I'll be very worried if it ultimately becomes necessary to pull the engine and send it back to this machine shop to have everything redone.

What a mess.
 
Again it depends on what was done in the rebuild.. If it had the exact same pistons (original), rods, cast crank, cast v. damper, and had the original tc the motor should have been just fine... If they just changed the bearings or did the heads it should be fine... If they changed any of the major balancing or rotating parts you have the possiblity of it being out of balance...
 
I think you have another issue with them not knowing what they did, and seeing how they charged you, but didn't do the work, or they don't remember doing it... I think legally everything is going to get fixed at their expense and time...
 
I'd find another engine shop. Sounds like they are totally incompetent. Were the pistons changed, was it bored out, or are your original pistons still in there, or does the shop not know that either?
 
cuda67 said:
I had a similiar problem with my 67 Barracuda for quite awhile. It had a vibration that was only noticeable at 50 mph and above. It was a seat of the pant, as the vibration you described. I always felt it was the driveshaft as my transmission had several tailshafts seals with very little miles. Finally, after many discussions, I took the drive shaft to be balanced, not expensive and as soon as they checked the shaft for runout they found variances of .020 -.060. I opted to have a new shaft built and no more vibration. Just a thought.
Click to expand...



If you havent narrowed it down by now. Cuda67 has a very good point here. I have been told if the driveshaft wasnt marked before removed this can happen. Your machine shop can check it for variances and if your already working with them they may not charge you.
 
pastortom1 said:
I feel your pain. If I remember correctly, the 340's are internally balanced. This means the balancer AND the converter must have NO counterweights on them....BUT, different years could be external......not sure.
Click to expand...

1973 340's were external balance.
 
Thanks again to everyone who provided input regarding my vibration problem. I think we have the problem licked. A tranny shop in my area rebuilt the torque converter and replaced the proper weights in the right locations. The vibration has gone away, plus the car feels like it's gained a few horses in the process. Maybe the vibration problem was affecting performance.

Anyway, I hope my problems are behind me.
 
When I built my 360 over ten yrs ago I remember telling the transmission guy, in fact I wrote it down for him to make sure the converter was balanced for a 360 and the nit wit gave me a neurtral balanced one. You will know right off if that's what it is, car will shake like hell, I thought the engine was misfiring. Lucky I didn't drive it much that way, probably at the very least would have damaged the main bearings.

This was after removing the trans and replacing it myself for the second time as the same dope that put the trans together made it so it only had high and reverse. I tried jb welding the correct MP balance weights on to drive it to his shop so he could take it out for the third time instead of me. The weights flung off and cracked the trans case. Spent weeks looking for another HD904 case that would hold the wider band. I orignally farmed it out to save time so I could bolt the engine together and disassemble the car. Won't make that mistake again.

When it's a Mopar you can always count on your farmed out work to add to the excitement. Good times............
 
Well, I'm glad to see you got the issues worked out... And just for the record all this information is here for the next guy to have... But as always if you've got a cast crank keep track of the original V-Damper, flex plate, torque converter, and the TCs position relative to the crank, it's part of the balancing act.... Hey, good luck.....
 
What kind of balancing did the shop do? They will have a record of this.

If it was internally balanced, you have the wrong balancer on it if the ORIGINAL one was re-used. Replace with a forged crank dampner, or buy a new one for about $100 for a neutral balanced engine.

If it was externally balanced, the ORIGINAL dampner would have been spun on the crank, and the shop should have asked for the torque covnertor and flex plate to balance it. If they did not ask for these and they externally balanced it, they created a problem, but you should be able to use a nuetral convertor and run it.

Here's the caveat... converotrs, even neutral ones, have soem weight on them to balance them individually.(like a gets balanced) You trans shop chould have removed the crank counterweight, AND the convertor's own balance weights, making the convertor out of balance now regardless of what you do. My question is, what did the tranny guys do with the weights they took off? There are marks, they can simply re-weld them in place.

On the living with it. You might be able to... but the engine and convertor cannot. At least not for long. Out of balance means the engine is trying (sucessfully) to eat itself up. Stop driving it until you know what needs to happen.
 
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