Need suggestions on vibration issue

-
J

jeryst

Well-Known Member
Joined
Jan 10, 2007
Messages
507
Reaction score
1
Location
Western PA
I posted this on FEBO, but there is not much participation there, so I decided to post it here as well. After all, a small block is a small block, regardless of what it is in.

I have a 73 Challenger. Originally a 340 4-speed car. Original motor blew up and was replaced in 74 with a factory 360 replacement motor. The motor is stamped a 74, and has no serial numbers, so this seems to support the story. I did not buy the car from the original owner, so I am not certain, but I am assuming that since it was a factory replacement motor, the replacement was done by a Chrysler facility under warranty circumstances.

Anyways, I have had the car for a few years, and really dont get to drive it much. I have always noticed that when I start to get on it, it has a vibration that shouldnt be there. It's a very high frequency vibration that makes the console and shifter buzz. Gets worse the faster you go, but I am positive its not a wheel/tire thing. I am pretty sure it is a drive train issue. There is no noise associated with the vibration, other than the noise that comes from the shifter, console, dash, etc. I revved the motor while in neutral, and it still seems to be there, just not as bad, so I am leaning toward an engine imbalance issue of some type.

I decided that this year, I am going to look into it, so I am looking for suggestions. Does anyone know what happened in a warranty motor replacement situation back then? Did they replace the whole motor, or just the short block? Could they have used parts from the original 340, like the damper, flex plate, etc, that may be causing the vibration? I know that some 340 parts are not compatible with the 360, and that a 360 was externally balanced while a 340 was internally balanced.

Any suggestions on what to look for would be really appreciated. I'd like to get some ideas and things to try before I start tearing things apart.
 
Crawl under and check for weights on the torque converter. Also check to see if the engine-transmission bolts are tight.
 
Make sure your flywheel is 360 balance one and your dampener is 360 as well, coarse if it's been driving that long and aren't the proper balance parts for the 360 it would most likely have shaken it's self to death already.

All the engines I build for 4spd cars are balanced at the machine shop (it can still be externally balanced in the case of a 360 but the rotating assembly has to be balanced in order for it to be smooth) it makes a huge difference in how the engine runs.

I am guessing it was an automatic engine that they put in and isn't finish balanced like it should be.
 
Check your harmonic balancer(dampner)for seperation,maybe the rubber ring has popped out causing an imbalance in the engine?Also check your torque converter for the weights.You can always take your d.shaft off and have it checked for balance too.
 
...........Run ur engine at idle with the hood up........park brake on.................lean over drivers fender so ur belly is resting on it rev it uo to 3-4 grand let off quickly and see if u can feel a vibration as the engine slows down.......if so u just found it.....more than likelt they used the 340 fw on the 360.......kim.......
 
73 340 is externally balanced....all 360s are externally balanced...

but they take different harmonic balancers and different flywheels...

you need to make sure you have a 360 damper and a 360 flywheel..
 
check the alignment of the bell housing with the crank (tranny drive pinion bearing retainer hole) Mopars are notorious for having to have this dead on spec.If out of spec you will get a vibration.I had someone bring me the same car as yours with same problem.They tried everything before asking me even tearing the motor down and balancing the rotating assembly.I checked the alignment which was out of spec made adjustments and problem went away.I may be wrong but I believe all SB balancers and flywheels are the same being that they are either for internal or external balance not motor size.
 
look on the front of the balancer...if they used the 73 340 balancer...that balancer is a one year deal..

It will say....For 340 cast crank only....if that is on there...that is half your problem...
 
jeryst said:
I posted this on FEBO, but there is not much participation there, so I decided to post it here as well. After all, a small block is a small block, regardless of what it is in.

I have a 73 Challenger. Originally a 340 4-speed car. Original motor blew up and was replaced in 74 with a factory 360 replacement motor. The motor is stamped a 74, and has no serial numbers, so this seems to support the story. I did not buy the car from the original owner, so I am not certain, but I am assuming that since it was a factory replacement motor, the replacement was done by a Chrysler facility under warranty circumstances.

Anyways, I have had the car for a few years, and really dont get to drive it much. I have always noticed that when I start to get on it, it has a vibration that shouldnt be there. It's a very high frequency vibration that makes the console and shifter buzz. Gets worse the faster you go, but I am positive its not a wheel/tire thing. I am pretty sure it is a drive train issue. There is no noise associated with the vibration, other than the noise that comes from the shifter, console, dash, etc. I revved the motor while in neutral, and it still seems to be there, just not as bad, so I am leaning toward an engine imbalance issue of some type.

I decided that this year, I am going to look into it, so I am looking for suggestions. Does anyone know what happened in a warranty motor replacement situation back then? Did they replace the whole motor, or just the short block? Could they have used parts from the original 340, like the damper, flex plate, etc, that may be causing the vibration? I know that some 340 parts are not compatible with the 360, and that a 360 was externally balanced while a 340 was internally balanced.

Any suggestions on what to look for would be really appreciated. I'd like to get some ideas and things to try before I start tearing things apart.
Click to expand...

Just one more idea, they used nylon bushings on the shifter arms to keep the shifter from vibrating. There are also steel bushings available for racing. It's supposed to give a tighter feel to the shifter. That might be what you feel. Just thought.
 
dodge71demon said:
I may be wrong but I believe all SB balancers and flywheels are the same being that they are either for internal or external balance not motor size.
Click to expand...

No they are different from engine to engine. The 340 externally balanced engine uses a different amount of weight on the flywheel and harmonic balancer than a 360 externally balanced engine. Same goes for externally balanced 400's and 440's. Even the old LA 360's are a different weight amount compared to a Magnum 360 due to different internal piston and rod weights.
 
May be The replacement motor was on auto trans and has not the pilot bushing .
In this case the input shaft and clutch are not centered . For test When it vibre .. slipp lightly the clutch and you will remark an different .
 
You must log in or register to reply here.
-

Back
Top