Engine vibration

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David Dickerson

David Dickerson

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I have a Duster with a 340 TA six pack motor that I have owned since 1979. After installing the 340, I always had a vibration issue that was most noticeable at cruising speeds. You could notice it in the rear view mirror. Assuming it was in the driveline since I had also swapped in a 727 and shortened driveshaft, I tried a few things to minimize it with no luck and finally replaced the 410 gears with 323's which just made it more tolerable because of lower engine rpm at cruising speeds. In 2000, I took the car off the road and decided to do a complete overhaul on the car, thinking that if I replaced all the possible culprits that gave me that vibration that it wouldn't reappear when the car was finished. Would like to mention that I had the engine balanced back in 1980 when it was first built. I replaced the harmonic balancer with an SFI approved balancer, and added a GV overdrive, so new balanced driveshaft also. Also replaced the engine and tranni mounts with urethane units (maybe not a good idea with vibration issues}. The car wasn't finished until 2018, but now seems to have a fairly substantial harmonic vibration while sitting still at 2500 rpm or higher. I don't remember the engine being like that before, though it did have rubber mounts. The vibration will vary depending on how the rpm's are brought up. Playing around with the accelerator can have an affect on it. I have tried everything externally possible to get rid of it. I first replaced the torque converter and flexplate, no difference. I unhooked all the accessories, no difference. I replaced the Summit balancer with a Fluidampr, no difference. About the only thing I can think to do now is pull the motor. The engine was completely rebuilt again this time around, so I'm having a hard time believing that it is something with the engine. Wondering if it could possibly be the input shaft on the tranni. I mention this because it seems that all my vibration issues back in the day started after putting in that 727. Someone told me that if the input shaft has runout or is bent that the pump wouldn't pump fluid into the torque converter, so things wouldn't even work properly. Unfortunately, you can't start the engine on a MOPAR with the torque converter disconnected. The last thing I want to do is to have to pull this motor since this is a beautifully detailed ride inside and out, and my gut keeps telling me that it isn't the motor, but the car just isn't fun to drive, and maybe not even safe to drive. Wish I had access to an engine dyno. Maybe replacing the balancer with one that wasn't used when the engine was originally balanced was a bad idea. Doesn't seem like it should be that critical. Any thoughts from those of you with knowledge of this subject would be appreciated.
 
Since your problem started when you switched the trans, one possibility is the engine/trans alignment. Might have to degree in the trans and run offset dowel pins.

With Studebakers, switching engine or transmission absolutely requires the two to be aligned to each other. It's usually not an issue with Mopars, but it can be.
 
I'll guess bad convertor or misalignment.
In Neutral or Park, with the car stopped ; The entire Geartrain in the trans, and in the GVod are stopped and not turning. The only things in there that are spinning are the front pump, the forward drum, the hi-drum, and the sunshell. You didn't mention the vibration quitting in Second gear, which anchors the hi-drum and thus the sunshell also,so that just leaves the forward drum, which is the smallest diameter.
In reverse the hi-drum and L/R band is applied, and the forward clutch is disengaged, so now only the outer case of the forward clutch is spinning at or near engine rpm, plus the planetaries. You did not mention vibration in reverse, so I'll go out on a limb and say the trans is fine.
That only leaves the TC.
And I'm sure you thought about that when you installed it, so it is either neutral balanced and the flexplate was balanced to the engine or vice versa, right?
Well in my thinking, that only leaves two things;
1) the guts of the TC or it's bearing. or
2) a misalignment of the crank centerline to the transmission centerline.
I have never had to check this
but I think the only way that this can be checked is by complete teardown of your transmission, the installation of a flatplate on the crank (like a flywheel) and then bolting the empty case back on. Now it's set up for the dial indicator.
Next remove the sparkplugs, and slowly by hand, turn the engine over watching the dial needle. You are looking for a readout in the pump-register of .007 or less. To change it, you remove the factory dowels , and install offset dowels in their place.
If you find yours is in spec, that, IMO only leaves the convertor. Sorry it couldn't be easier, but you already did all the "easy" stuff.
Happy HotRodding

Let this simmer for a while; there are smarter guys than me here that might think of something else.

OOps treed already,lol
 
I'd try rubber mounts for the engine and trans before I did anything drastic, and make sure the exhaust isn't mounted too rigid or hitting anything.
 
You can’t just swap a damper for another one unless you know how the balance job was done. Start with that because you can’t just swap stuff like that unless you are positive you know exactly what you have.
 
If it was internally balanced, I can't imagine a Fluidampr throwing it off enough to cause a vibration......especially since it didn't change when he swapped out the Summit balancer.
 
cudamark said:
If it was internally balanced, I can't imagine a Fluidampr throwing it off enough to cause a vibration......especially since it didn't change when he swapped out the Summit balancer.
Click to expand...


If they used the Summit damper to balance the crank and you swap it out it will shake like a dog pooping peach seeds.

It’s a piss poor balance job but it happens all the time.
 
According to the OP, it vibrated before he changed the balancer, and didn't change afterward. Not likely two balancers produced the same vibration. It just wouldn't be my first candidate as the problem.
 
You eliminated the front accessories , swapped some other items , like cudamark mentioned in post #4 you should reinstall the rubber mounts , I would even try putting a rubber trans mount in to see if it changes something while in different RPM ranges. Good luck.
 
A few things to check:

1. Did you knock the balance weight off the drive shaft? May want to pull the drive shaft and have it balanced.
2. When you switched to a 727, did you get a neutral balance converter AND flex-plate?
3. Check that transmission mount again...also make sure the motor is sitting square.
 
cudamark said:
According to the OP, it vibrated before he changed the balancer, and didn't change afterward. Not likely two balancers produced the same vibration. It just wouldn't be my first candidate as the problem.
Click to expand...


I missed that part. OTOH, I’ve corrected many balance jobs. @lead69’s brother had a shaker that we rebalanced because it shook like a dog pooping softballs.

I’m betting it’s in the balance job somewhere.
 
David Dickerson said:
I have a Duster with a 340 TA six pack motor that I have owned since 1979. After installing the 340, I always had a vibration issue that was most noticeable at cruising speeds. You could notice it in the rear view mirror. Assuming it was in the driveline since I had also swapped in a 727 and shortened driveshaft, I tried a few things to minimize it with no luck and finally replaced the 410 gears with 323's which just made it more tolerable because of lower engine rpm at cruising speeds. In 2000, I took the car off the road and decided to do a complete overhaul on the car, thinking that if I replaced all the possible culprits that gave me that vibration that it wouldn't reappear when the car was finished. Would like to mention that I had the engine balanced back in 1980 when it was first built. I replaced the harmonic balancer with an SFI approved balancer, and added a GV overdrive, so new balanced driveshaft also. Also replaced the engine and tranni mounts with urethane units (maybe not a good idea with vibration issues}. The car wasn't finished until 2018, but now seems to have a fairly substantial harmonic vibration while sitting still at 2500 rpm or higher. I don't remember the engine being like that before, though it did have rubber mounts. The vibration will vary depending on how the rpm's are brought up. Playing around with the accelerator can have an affect on it. I have tried everything externally possible to get rid of it. I first replaced the torque converter and flexplate, no difference. I unhooked all the accessories, no difference. I replaced the Summit balancer with a Fluidampr, no difference. About the only thing I can think to do now is pull the motor. The engine was completely rebuilt again this time around, so I'm having a hard time believing that it is something with the engine. Wondering if it could possibly be the input shaft on the tranni. I mention this because it seems that all my vibration issues back in the day started after putting in that 727. Someone told me that if the input shaft has runout or is bent that the pump wouldn't pump fluid into the torque converter, so things wouldn't even work properly. Unfortunately, you can't start the engine on a MOPAR with the torque converter disconnected. The last thing I want to do is to have to pull this motor since this is a beautifully detailed ride inside and out, and my gut keeps telling me that it isn't the motor, but the car just isn't fun to drive, and maybe not even safe to drive. Wish I had access to an engine dyno. Maybe replacing the balancer with one that wasn't used when the engine was originally balanced was a bad idea. Doesn't seem like it should be that critical. Any thoughts from those of you with knowledge of this subject would be appreciated.
Click to expand...
I have this same issue at 3000 rpm in park and going down the road.
340 w/727 this appeared after I swapped in a new SFI flex plate and Hughes 3000 stall converter both neutral balanced.
 
Converter support bushing, probably not the real name, but you know what it is. I would unbolt it from flex plate and see if it rocks. Might be hard to do, because if you push it back it might lie to you. It will be on an area of the bushing that normally doesn’t get used.
 
furrystump said:
Converter support bushing, probably not the real name, but you know what it is. I would unbolt it from flex plate and see if it rocks. Might be hard to do, because if you push it back it might lie to you. It will be on an area of the bushing that normally doesn’t get used.
Click to expand...
Are you talking about the bushing in the pump?
 
Sounds similar to a problem with a LS Chevy motor. -- It was the torque convertor. Some how, it was out of balance. -- New convertor - problem gone.
 
TT5.9mag said:
727 front pump/bushing help
Click to expand...
After doing a little homework it could be the pump bushing, but in my case I dont think it is. Within the past 4 years I have had 3 different converters in the car, did not have the issue with the first two only the current one. I think I got a bum converter from Hughes that is out of balance.
 
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512Stroker said:
After do a little homework it could be the pump bushing, but I my case I dont think it is. Within the past 4 years I have had 3 different converters in the car, did not have the issue with the first two only the current one. I think I got a bum converter from Hughes that is out of balance.
Click to expand...
With that last piece of juicy information, think you've found the culprit.
 
I wanted to throw my $.02 in, I had a similar situation and its nerve wracking, I even swapped engines, vibration still there, ended up being a bad clutch pressure plate. I found out through "process of elimination" LOL! I actually put the flywheel on a wheel balancer and it came up zeroes...just to check that, and had driveshaft balanced etc I threw everything at it.
 
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