Trouble with vibration....

[Docholiday72tx]

smelling burned asbestos....sounds like it's time to have the fly wheel surfaced, with a side order of clutch, pressure plate, and throw out bearing.
Doc

[rjewkes]

juat a thought but what about the trans mount? Wouldn't explain asbestos but could be what cuased the flywheel warpage or binding.

[Mikey]

Doc,
That's what I was thinking. How tough is this project and what would I expect to pay doing the work myself?

It's possible that the vibration is causing the clutch to not fully engage so that's why this vibration problem is vital for me to track down first.

The reason I feel the engine and transmission mounts would not be it is that when you accelerate while in neutral, then you should be able to make the engine rock on the worn out mounts. Something is causing the vibration yet the engine is pinned down pretty good. Transmission mount probably wouldn't be it since all my diagnosing is in neutral and stopped.

One of my buddies suggested running #1 to TDC and checking the timing marks to confirm no outer ring slippage of the harmonic balancer...and if I was on a compression stroke, I can pull the distro cap and check how close the rotor is to #1 to check chain stretch. Ad that to my TO DO list!

This problem is starting to get on my nerves, I tell ya. Kinda hard to convince the wife to keep a boat anchor!
Thanks,
Mikey

[Mikey]

Keith,
The truck hasn't been driven much since I got it but I don't recall any pulsing problems in the clutch. When I looked at the area between the 3 speed and the engine, it didn't look like it had an inspection plate like on the C4. I need some way to evaluate the flywheel without a major ordeal. I was considering pulling the starter but I don't think you can see much. My experience is almost exclusively with C4s and AODs with a bit on T5s.

My thought is the vibration may be transmitted to the clutch and causing the clutch engagement problem...which seemed somewhat intermittent. Kinda chicken or egg syndrome. Ditto on the mounts.

Thanks a bunch,
Mike

[Chasbod]

Here's a wild thought.....harmonic balancer? Could the clutch pressure plate be a culprit...it's always spinning....has lots of springs.

If the engine isn't misfiring and accelerates smoothly then points, plugs, timing, plug wires shouldn't be an issue. Has to be something mechanical.

[Chasbod]

bad fan blade could cause vibration too.

[Mikey]

I plan on really checking the harmonic balancer this weekend.

The thing feels exactly like a misfire so I'm going to try pulling one plug wire at a time to look for a change. Perhaps a plug is grounding out through oil or the block thereby firing my timing light but not a piston. I put in an old set of plug wires to see if that did anything. Here is a summary of things I've looked at so far:

Vacuum lines
Firing order
Points gap
Changed to another spare set of plug wires
Timing (timing mark is steady)
Compression is excellent..all between 120 and 130
Choke is good
Removed belt from alternator and water pump...still there
Put timing light on each wire and each one fires
Check wires at night and saw no sparks
Tried a MSD Blaster coil
Diaphragms on distributor
Motor mounts seem ok

Now you can see why I'm getting frustrated!

[Chasbod]

if you had a hard time shifting into gear, i was thinking about the pressure plate having a problem. It's basically a set of individual levers and springs that have to all work together to release the plate from the clutch disk. If it's really old, could be something internally screwed up and throw things out of balance...just a longshot.

If a plug had a cracked ceramic insulator, it could be leaking voltage to ground.

Carb jets and air passages all clean? Fuel/air adjustment ok?

I know it's a hassle but I used to enjoy the challenge of figuring something out like this. Sure gets your mind of all the other stressful stuff in life.

[GT-Racer]

You changed plug wires but what about the plugs? Did you check them out? And like chasbod said if the porcelain is cracked it could jump to ground (exhaust) This is an easy check though just start the truck up at night and look for sparking.

[Mikey]

OK,
Based on all your great replies, here's this weekend's TO DO list:

***Check harmonic balancer by bringing #1 piston to TDC @ compression. Check timing marks..pull distro cap and check rotor for #1

***Check or trade out distro cap to see if it's cracked

***Pull one plug wire off at a time looking for a significant change. If one gives no change, Bingo! This should isolate a bad plug.

***Check plug wires again at night

***Check distro to ensure weights and springs are in good order

***If someone can tell me an easy quick check on the flywheel/pressure plate, I'll check that too. NOT going to separate engine from tranny!

Am I missing anything simple??? I want to grill and goof off this weekend!!
Thanks,
Mikey

[68F250]

Could be something gone amiss in the pressure plate assy. causing an imbalance. Might be why its not holding well too.

Or the harmonic damper has slipped. Not the outer ring, that can slip around 360* and not cause a problem. I'm talking about the whole hub assy. has slipped on the crank snout due to the key being loose or breaking. Small blocks are externally balanced at the front hub and the flywheel.

[Docholiday72tx]

I don't know of an easy way to check the clutch and pressure plate with out removing them.
I replaced the clutch pressure plate and throw out bearing between a 390 and 4 speed about 4 or 5 years ago. They sell a clutch kit for about 150 bucks, which includes the clutch, pressure plate, throw out bearing, and clutch alignment tool.
Doc

[72hiboy4x4]

I doubt it's your timing chain....if it jumped a tooth it would be a lot worse than a slight vibration. If it ran at all it would be VERY rough.

Hey Keith,
on my '88 460, when I bought it it seemed like it was lacking a little power (at least what I thought a 460 should have). ran and drove very smooth, tho.
towed my little car 2 1/2 hrs home and drove/towed with it for about 5 months before it finally stalled on me towing a very heavy school bus up a very steep hill.

anyways to make a long story short, I finally figured out it was the timing chain- or rather, it was the timing gear keyway and key were wore almost in an 'L' shape. about 40 deg. of slop on one side! probably a 460 thing. but anyways, a loose timing chain won't always make an engine run bad.

BTW here is what it looked like.

[DuckRyder]

I too vote for clutch/pressure plate problems.

A broken spring or lever in the pressure plate could cause both the vibration and clutch problems.

[Mikey]

Well, I will check the simple things first.

I remember, now that you guys mentioned it, that the harmonic balancer on my 79 van had broken apart at the key. Weirdest thing, the balancer cracked off the ends until it fell apart and created a heck of a racket. I'll check that.

Last night, I re-checked each spark plug, cleaned off any oil, inspected each one and re-gapped all. No luck. I keep zeroing in on ignition as that what it feels like.

Anyway, it's looking like it will be the clutch/pressure plate. How difficult is that to change? Doc, where did you get your kit?

I've got to get this thing running so it doesn't turn into another yard ornament!