1978 Dodge 360 / 727 B300 maxi van.

Vehicle has idle vibration, I am told that either the weights fell off, or the TC was changed to a non weighted one.

AS the TC is otherwise fine, I am told to get a weighted flexplate.

My question is, are they all the same? I mean, as the engine is externally balanced, is the weight just "standard" for all, as long as I get the correct one for my tranny?

I am also thinking that if a weight fell off, can I replace it?

Thanks!! I have searched on this and would really like more info before I drop the tranny.....!

 

These were standard "from the factory." If someone has radically changed pistons, stroke, or rods, it may NOT be "all that balanced."

There's plenty of talk on the wwwdot about "welding on your own weights." Frankly, I doubt that anyone can get a TC weight installed as per "factory equivalent" or in other words balanced by welding it yourself. Maybe.

Stop and think. If a weight "that small" vibrates a 400? pound mass enough that YOU CAN FEEL IT through the mounts and mass of the body/ frame, then you have a LOT of force in action there

It's easy to tell, just pull the bottom inspection cover and look for the two weights. You'll easily tell if they are gone--you'll see where the weld broke off, or in the case of a 318 TC, there won't be any.

I ALSO would not assume this is your trouble. Try running the engine briefly with the belt(s) disconnected, you might have a dent in a pulley, chunk out of a belt, etc, or in my case, I once had "hang on" AC which used those off-center idler pulleys for tension. If you didn't get just the right belt length, and get the idlers just right, at certain speeds that belt would "resonate" and vibrate like mad.

Another thing to check is the balancer, which can slip the outer ring. Easy way to do that is check for true TDC, which is easy. Build or buy a "piston stop," like this:

http://www.jerrybramlett.net/images/...stallation.jpg

Remove the no1 plug, make sure the piston is "down a ways" and install your stop. If you build one, you'll have to estimate that it will hit the piston at some point. Disconnect the battery ground for safety, and use a wrench to rotate the engine until it stops "on the stop." Make a temporary mark onto the balancer directly under TDC on your timing tab. Do the same thing rotating CCW. You'll now have two temporary marks on the balancer, and true TDC will be halfway between. If the old one is OK, that is where it will be.

 

Thank 440, I have run without belts and the vibration is still there, the harmonic balancer inspects OK and is not weighted, I am told....

So, if I remove the plate and see no weights but I CAN see a weld spot, then I can assume that the weight fell off?

I agree about welding on weight...! Yea, pretty mighty these Mopar Gassers!

 

Yup exactly

 

Did this happen all of a sudden? Does it do it in netural or driving ? If it has the correct vib damper it should be 1 1/2 to 1 3/4" wide the 1 1/4 wide is for the 318 Pull the starter and the inspection plate examine the Torque converter weight but I doubt it fell of. The vib damper DOES have a balance factor.
You could also have a cracked flex plate, have you checked the motor mounts? The weighted Flex plate actually looks like a big pie with a bite taken out of it

 

Thanks for the responses..

The vehicle is new to me, and it did this when I bought it. The vibrations are noticeable in N when revving to maybe 800. The vibration does not really stop at higher revs but become less noticeable - almost negligible. I have examined the damper and it is not separating as far as the eye can see.

Motor mounts are not too bad I did check them, the rubber is not noticeably cracked etc. The drivers side seems a little "loose" the motor shifts a little more than I believe it ought to when revved with the brake on. Maybe an inch...

Let me see how the inspection looks. I have no way of knowing if the TC is original, except the previous owner did install a RV cam - i looked it up and it is very mild. However, it is 'possible' that he changed the TC as well and I do nto have the record, however that seems unlikely as he kept fairly good records going back to 1978. The only indication is that this TC is (I believe) supposed to be a lockup and it does not seem to do that....shifts like a bull however, fluid is very clean, good smell...

Nice to have a Mopar 360 to fool around with, as I do not camp much the gas is not an issue which is a good thing.....

 

If you have checked all the obvious things I would suspect a bad converter possibly
I had a van with a 360 that had a vibration too never did figure it out the Van got totaled.

 

...thought I would finish up since I had not.

the issue turned out to be.....rear tranny mount..! It was GONE and the output shaft is real long on the van and developed a good amount of shimmy...

the way I finally diagnosed it was (beside looking at the mount...) while sitting in the van with the dog house off, I revved it up until i really felt the vibration...then I placed my hand on the bell housing....no vibration there...i was feeling it in my seat through the frame....but the actual engine / tranny, nothing out of the ordinary....that tipped me off that it was, in fact a mount.....hope that helps...!

 

!! GREAT !! I guess sometimes I assume people have done/ checked the simple stuff. A deceased friend of mine had a mid- 70's Ford pickup that he kept up like new. Someone replaced the clutch, and he went through MONTHS of trying to find out why it chattered. Turns out one of the cab to frame mounts was bad, or loose, even though to look at it, it appeared OK.