Vibration

[xx88man]

I have a 1974 Challenger 360 auto. When running I can feel a very noticeable vibration... stopped in park or neutral. I know it needs a transmission mount so my question is this. Can a bad transmission mount cause this vibration when the car isn't even moving? It seems to be a vibration that comes in waves.. rough for half a second then smooths out for half a second when I'm bringing up the RPM.

[MoparLeo]

Is this something that just popped up or has any recent work or changes been made ?

[xx88man]

I have only owned it a couple of months. Bought it from someone that wanted to get rid of it and it wasn't running when I brought it home.

[73_Cuda_4_Me]

My 340 had a similar issue when I first got it (oscillation every 3 seconds that you could feel right up through the seats), and after much trial and error, ended up finding the TC to be the culprit. PO had replaced original with like a generic off the shelf one (when they installed a truck 727 from 73), supposedly for external balance. I replaced it with a better quality torque converter, and everything smoothed right out.

 

[xx88man]

My 340 had a similar issue when I first got it (oscillation every 3 seconds that you could feel right up through the seats), and after much trial and error, ended up finding the TC to be the culprit. PO had replaced original with like a generic off the shelf one (when they installed a truck 727 from 73), supposedly for external balance. I replaced it with a better quality torque converter, and everything smoothed right out.

 

Thanks for your input!

[bdschnei]

Since you're talking about a 360 with a vibration and you're new to the car, make sure to check that it has a properly weighted balancer and torque converter (or flex plate). You'll find lots of discussion about that problem on this forum as well as others, but the short version is the 360 is the only mopar small block crank that's eternally balanced via the balance and torque converter. 

[xx88man]

I can't figure out how to post a picture here. The balancer has a thin metal collar in front of it that appears like it could be a weight. I assume there's no way to get a good look at the tc without pulling the transmission?

[bdschnei]

I've attached a picture of both a stock balancer and torque converter. As you can see the additional weight is cast right into the body of the balancer. If you remove the converter bolt access plate and rotate the engine you'll be able to check for the converter weight.

[xx88man]

bdschnei thank you for that picture! I'll definitely check for that weight. My balancer looks right

[xx88man]

Does anyone know how much the weight on the torque converter should weigh? 1974 Challenger 360/727

[Mr Cuda]

19.79 in. oz.  A number that the balancer people can use. Not a static weight
A number straight from the mopar  performance book.

[xx88man]

19.79 in. oz.  A number that the balancer people can use. Not a static weight
A number straight from the mopar  performance book.

Thank you this helps. Has anyone here ever tried using a magnet in place of the weight to try to fix a vibration?

[Mr Cuda]

That would be one hell of a magnet.
Centrifugal force would fling it.
 I once clipped a wheel weight onto my clutch cover to prove imbalance.
 Then pulled the motor apart and balanced everything.

[xx88man]

Okay so I finally had the chance to check. My torque converter has the weight on it. I'm back to square one with this vibration

[MoparLeo]

Just to eliminate it, try putting a timing light to it and check for timing fluctuation. Also check vacuum for fluctuations. this will eliminate tuning issues.