My 25 coupe always had the usual shakes and rattles but it has developed an engine and/or transmission vibration. It's an older rebuild from the 60s. It's not the drive train because it vibrates sitting at an idle and increases with more throttle and is more pronounced while driving.
What should I be looking for prior to and after pulling the engine?
Your help would be appreciated.
Sounds like your muffler bearings just went bad.
Lol ok but seriously while the engine is in I would pull the transmission door (trapezoid shaped cover, not the whole hogshead) and make sure everything that you can see looks snug, no magnets anywhere crazy (helps to have a helper slowly crank engine around. You can also look through the starter hole (REMOVE BENDIX FIRST).
Then I'd pull the oil pan cover and verify that none of your connecting rods or bearing caps are loose. You can also get a good/different view of magnets when looking towards flywheel from oil pan. That's about all I've got, not sure other than throwing a magnet or a bearing wearing out you would develop a new vibration. There are experts here who have forgotten more about this than I know though, I'm sure they will help!
Thanks Seth, I appreciate the input.
Can the fourth main cause a vibration? It's interesting to me that there is no sound associated with the vibration.
I think that Seth's method of checking for 'looseness or slack in the engine' is what I would do.
You mentioned that's it a rebuild from the 60's which is 50 or more years ago.
By now if the car has been used a fair amount something by now needs adjusting such as the mains or rods.
I would drain the oil and remove the trans cover and oil pan and check to see by having someone SLOWLY hand crank the engine to see if there is any movement anywhere. I would do that first to begin with.
Seth is right on. Something changed if the vibration is a new development. That is an item went out of balance such as a magnet falling off and dropping clear without hitting anything throwing the flywheel out of balance. Actually I can't think of any other part that would fall off and cause this vibration. As to mains: it's no-go for a vibration here. Noise? Yes. But I don't believe that's the cause of what you describe.
Yes, the 4th main could allow vibrations of it were badly worn. You would more expect to notice it while driving and maybe not so much sitting still in neutral. However, even in neutral, it still supports the tail end of the transmission main shaft, (through the output shaft), which is bolted directly to the flywheel.
When scouting around, also look for a missing clamp plate and spool from the magnet ends.
Also, look for a broken motor mount ear. It may not be broken completely off but, enough to allow some extra flexing. This may be especially true if you've left out the wood blocks that sit in the frame channels and that back up each mount arm to give it rigidity and support. (Yes, I know some of you say "you don't need those", well; you do.)
Our 14 started viberating a little and before long we were in the trouble trailer with a broken crankshaft!!!!!!!!!!! It will not heal itself and a tear down might save you a lot of money? Bud.
Thanks everyone, these are great suggestions.
I do see that the crank pulley pin is completely loose and I'm sure centrifugal force sends it to one side of the crank while running. I this a possibility?
As I've had time to think about it more do some easy stuff first - make sure that your timer is clean and wired well, that your coils are all ok (if you have a spare try swapping it around different spots) maybe you're just firing a little funny. If you have a cover plate centering tool make sure that your cover plate is centered, if it's off that would mess up your timing and maybe make the engine run a little rough and vibrate a little more. Check your spark plug wires, the spark plugs themselves that they're clean and gapped correctly (also good time to make sure they're colored correctly, that can tell you a lot).
If you get through all of that and haven't found any kind of smoking gun then double check your nose clamp, the 2 bolts that hold down the front of the engine where the crank is, those should be safety wired as well. Then check your pan ears where they bolt to the frame, there are two on each ear, one vertical and one horizontal.
Keep progressing and while you have the oil inspection cover off and are looking back at the flywheel, make sure you see all 4 bolts that hold the transmission to the crankshaft and that they're still safety wired together (usually 2 and 2). Pull your valve gallery covers off and verify that you don't have any valves sticking anywhere. And then follow my earlier advice about checking into different areas. You can also make sure that the oil pan and hogshead bolts are all nice and snug.
Have you done anything lately? Maybe changed the oil, looked at something, any type of maintenance? That's usually the easiest way to figure out what got gooned up.
If you go through all of the advice in this thread and you still can't find anything that gives you an "Ah ha!" moment, I'd consider pulling the engine and really going through the whole thing. I'd be really surprised if you find nothing at all though, it seems like something had to come loose or something in order to go from what you are used to and then all of a sudden have a new/different vibration. Keep us posted as to what you have checked and found.
I think not. How much does that pin weigh? A couple of ounces?
Referring to the crank pin, not what Seth said.
Seth is right. Check your ignition to be sure you have spark to each plug and that the plugs are all working. You can set your parking brake and with a fast idle, ground each spark plug to the head. As you ground them one by one. The engine should slow down or run rough. If grounding one spark plug doesn't affect the running of the engine, you have trouble in that cylinder.
Check the timer, the wiring, the coils and the spark plugs. If you are sure it is firing at each spark plug, do a compression check. All cylinders should have even compression. If one is very much lower than the others, you have a problem with the rings or valves. That will take an engine overhaul.
Another thing to check is for noticeable "knocks". If shorting a spark plug either intensifies or decreases a knock, you will also need to do some "tightening up".
Let us know what you find after doing these tests.
Other vibrations could be caused by broken motor mounts. Check the ears on both sides of the crankcase to frame. There should be no cracks here.
A loose flywheel could also cause a vibration accompanied with a knock.
Wasn't thinking about the "4th. main" until Jerry posted. I suppose he has a point too although I don't recall seeing it mentioned on the Forum as a source for vibrations before. It might not move as much under a load as free wheeling in neutral. I don't know. As to the front pulley being loose/worn: I don't think it has the mass to cause a bad vibration. It'd have to be pretty sloppy before I bought that one.
How about just feeling it with the engine running or using the broom stick as a listening device to try to hear anything strange. I feel if it was the 4th.main the whole driveshaft housing would "sing" along with the bearing.
The mains will cause a vibration which usually can be felt through the floor boards while driving. KGB