Trouble with vibration....

[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!

[Chasbod]

You will have to pull the tranny, not sure if you have a bell housing w/ inspection plate. Regardless, the pressure plate is bolted to the flywheel and sandwiches the clutch disc between the pressure plate and flywheel surface. The throwout bearing is what presses against the pressure plate levers which then disengages the pressure plate from the disc when you push the clutch pedal down.

The clutch pedal free-play is the 'slack' that the pedal has to make sure that when you release the clutch pedal, the throwout bearing comes completely off the pressure plate levers to make sure the full pressure of the plate is on the clutch disc and pushes it firmly against the flywheel.

In short, when you remove the clutch arm which has the throwout bearing attached to it, you will then unbolt the pressure plate which is under full load pushing the clutch disc to the flywheel. Once you remove the pressure plate, the clutch disc will be free and fall out w/ the pressure plate.

This is why you need a clutch alignment tool to reinstall the clutch disc. To reinstall, you will align the clutch disc to the flywheel using the special tool (i've used a broomstick before), then you have to bolt the pressure plate back to the flywheel. As you bolt the pressure plate back on, you will put the clutch disk back under full load.

I would make sure your fuel/air adjustment is good on the carb before pulling a tranny to get to the pressure plate.

[Mikey]

Duly noted! Tranny work is last resort!

Thanks for the write up. In all my hot rodding years, I've never replaced a clutch....mainly 'cause I've always had automatics.
Thanks all,
Mikey

[68F250]

I think you're gonna have to pull that tranny and change the clutch too. Put a jack under the rear of the motor 'cause it's gonna want to tilt backwards after the tranny is removed. Rent a tranny jack to make it a lot easier. I've used the "chest" method before but at our age I think a few bucks is worth it compared to a few sore ribs.

If it's any consolation, I don't think the timing chain has jumped because you'd never get that high a compression reading. You can easily check the chain slack, put a big socket and breaker bar on the crank bolt and turn it in one direction. Now slowly turn it the other direction a little bit. You can feel the slack as it goes from being easy to a little harder. Using the timing marks as a guide, anything more than 16 degrees of slop going back and forth means it's about ready to jump. This method is measuring the slop in both directions so 16 degrees means it's running 8 degrees out of time. 200K is a lot for a chain, they're usually worn out by 100K especially if it's the original nylon coated sprocket.

[Mikey]

Well, guys,
Truck went back to the prior owner. He still needed it for a few years. I will be helping him fix it later when he can get to it. I'm printing your instructions for when we get to the fix. His wife wanted him to keep it as did mine. Guess I'll be back working on my 74 Bronco. Visit me sometime at www.classicbroncos.com as Mikey.
I'll keep checking back to try and help occasionally if they don't block it at work.
Thanks for all your help. You guys are great!!!
Mikey

[tynall44]

is it a automatic if so somebody might of put a 300 six cly fly wheel in it

[willowbilly3]

f it only vibrates when you run it up no load then don't do that. Engines were not made to be run up with no load and it is not good for them. You can check how much slop is in your timeing chain. Line up the timing marks. Now take the crank pulley in your hands and rock it back and forth, easir with the plugs out but not necessary. You will be able to feel the resistance of the cam when you hit the end of the chain slack each way. Note the extremes on the timing pointer. Even a healthy low mileage engine will have 2 or 3 degrees. 6-8 is still acceptable and over 10 is getting tired. I have seen 16-18 degrees slop on some tired engines and at 20 it is about ready to mutiny.
If you have a stick shift (smelling burned asbestos) sounds like you are ready for a clutch. Maybe the pressure plate threw a waight.

[LUB69F100]

Speaking of vacuum leaks....power brake booster?

Lub
69 FLH
69 F100