[YNOT]

All of a sudden tonight my 89 5.0 GT 5-speed shakes bad over 2,800 rpms (in 1,2,3,4, didn't try 5th). I reved it out of gear and same thing.

It has 134,000 miles and I just did a oil change, new coolant, Mr. Gasket 180* high volume thermostat, Summit Racing high volume waterpump, Sealed Power double roller timing chain and gears, NAPA gold air filter.

Oil pressure was fine, and temp still reads 153*, it read the same with the old thermostat so I'm guessing the gauge is off.

Is my top radiator hose suppose to be hard when the car is hot?

[Tony_90fox]

Change your cap and rotor. Possibly plugs too.

[YNOT]

Which Cap, Rotor, and Plugs are recomended?

Couldn't be my harmonic balancer could it? I mean that can only go on one way (straight) and then it's torqued hard.

[nolife]

Harmonic balancer? Sometimes they are easy to troubleshoot because the rubber strip is misplaced or no longer even or the outer ring is not aligned with the inner ring (either moved in or out), or the outer ring will move by hand or when lightly tapped. Mine failed suddenly after a missed shift and the car was only drivable under 1500 RPM. If I wasn't less then a mile from my house, I would have had it towed.

Top rad house? Yes, it does get harder because of the pressure when the water is hot.

[Tony_90fox]

Yes it can be the balancer too. I had the same problem, it was more of a miss, but shook HORRIBLY! I just went with cheap Accel cap and rotor and that fixed my problem.

[YNOT]

My top radiator hose wasn't hard when I got home.

[nolife]

My method of narrowing down between a miss and balancer was to attach my timing light to each individual wire and look for a miss. Of course that would not help if it was a plug or not and quite honestly I don't know if I would have noticed a miss by looking at the light. When I did wire 1 (the last one I did), I aimed it at the timing mark on the crank and saw pieces of rubber hanging out from the harmonic balancer. It was all to clear at that point what was wrong.

[Tony_90fox]

Possibly even a fuel filter?

[homebrewed]

I think the wobbolator countershaft fell out....

Are you spillin' any coolant anywhere? You upper hose should pressurize real fast. If not, your cooling system is backed up or gone south.
Snag a timing light or a really bright xenon or halogen flashlight and take a peek at the harmonic balancer. Look for anything hanging from it or pieces missing.

[YNOT]

no not leaking coolant.

[weems]

I would be willing to bet anything that this is a harmonic balancer issue, my car did the same thing and that is what it was. Take a look at the balancer when it is cranked and you might even be able to see it wobbling.

[YNOT]

Looks like it's wobbling, but how could it be, it goes onto a shaft that is a press fit.

[YNOT]

Was just out looking at it running and all of a sudden I only had one fan bolt holding it on, ran to shut the car off when it starting hitting the shroud. Good thing I was watching and in the garage.

Off to go buy loc-tite.

[nolife]

If it is woobly or physically loose, that is definetly your problem. I would stop running the car until you get it replaced.

The balancer is two pieces, outer and inner ring separated by a piece of rubber squeezed in between. Only the inner part is attached to the shaft. The balancer is not really press fit. Well it does "press on" but not in the manner that you need a hydralic press, heat, or some special tool. It is held on to the crankshaft by a 15/16 bolt and you will need to use a large gear puller or a harmonic balancer puller after that bolt is removed.

FMS-M-6316-M50 is the Ford Motorsport replacement (50oz model). It is about $70 from the common performance parts places.

[YNOT]

Sorry just had to look up the definition of a harmonic balancer. So the rubber it maybe wore out on the balancer. I half-ass used a gear puller to get the balancer off before.

It was such a sudden vibrate, it didn't slowly build up. Can a harmonic balancer be fine one second and total junk the next?

[YNOT]

Just took the serp belt off and reved it over 3,000 rpms real quick and it didn't vibrate, so maybe it isn't my harmonic balancer and it was only my fan falling off.

[angermgt]

lucky

[nolife]

A loose fan is much easier and cheaper to fix.

Yes, a harmonic balancer can suddenly fail, mine did.

[GSUJake]

I would bet that your harmonic balancer is bad.