BAD vibration TKO600

[chpr1972]

I put this in wrong place. I have a vibration at 60 mph in 5th gear, at about 1800/1900 RPM in seat of the pants. Below that, there is no vibration. I normally drive around town under 60 mph. The other night I needed to change lanes, so I stepped down on it to about 70 mph. It vibrated so hard that I thought rear end might come outta the car. I pulled the rear tires and vibration is still there. There is no vibration in motor to 4000 rpm. With the drive shaft out, it is hard to tell if there is a vibration in the transmission. U joints check good, free and no play. Since the rear end [Ford 9" 370 gears with clutch pack] was leaking, I pulled it and had a guy at 4x4 garage look at it and found nothing wrong. There is 12,000 miles on the car. I recently had to put new cam/ rod/ main bearings cause rear cam bushing was installed wrong. A new clutch disc was installed also. !966 Lemans with factory setup Hotchkis 1" dropped springs with lift bags. The upper arms are adjustable. I have reset it 3/4 times at least. Last time I used speedways formula and .5 is where it is at and within point 5 is good. I also used Tremec phone app. It checked good, all green 01.3/00.6/00.7

[AU Doc]

Driveshaft out of balance?

[chpr1972]

All the weights are on the shaft. u joints are free and smooth. I had the shaft built with with 4" shaft and I do not know which U joints were used but they are about 4" across. I would guess 1330 as it is a Moser rear end if that helps. There is 12,000 miles on it.

[chpr1972]

All the weights are on the shaft. u joints are free and smooth. I had the shaft built with with 4" shaft and I do not know which U joints were used but they are about 4" across. I would guess 1330 as it is a Moser rear end if that helps. There is 12,000 miles on it.

[AU Doc]

When you say you pulled the rear tires, did you run it up to 70 on jack stands with no wheels? I'm not recommending that, just clarifying what you mean.

I would say as a first pass my thoughts on a vibration as bad as you describe are first it's the tire/wheels, next driveshaft balance, driveline angle, and then possibly a broken harmonic dampener or out of balance flywheel (not sure if your engine is externally balanced or not). For a vibration as bad as you describe, I can't imagine there's anything in transmission that would cause that and it still function. I've had a harmonic dampener separate and cause a terrible vibration.

EDIT: Those cars have a pretty long driveshaft, don't they? Any chance you're hitting one of those critical speeds?

[minendrews68]

ok, if I understand correctly, you pulled the drive shaft and ran the car up to around 70? With no vibration you've eliminated the engine, clutch, trans, unless this only happens when there's a load on them. Then you pulled the rear wheels and still had vibration, is this correct? If so, you've got a best bet driveshaft. (It could be other things less obvious). I would suggest pulling the drive shaft and possibly taking it back to the place you had it made. Have them check it out. You also felt the u-joints but nothing felt out of place? take the end caps off the u-joints that aren't pressed in and examine what's there. I have a 2500 silverado 4x4 that had a vibration, although not quite that bad. Took it to the dealer and they checked it out and said the u-joints were fine. I brought it home and tore into the joints to find that they were not fine. Replaced them and problem averted. as stated before check out harmonic balancer. Did this come on all of a sudden, or when did you notice it?

[minendrews68]

Did you ever find the problem? I'm sure people are curious..

[shelteredchevelle]

I'm following this too because my TKO has an odd vibration in it too. Low rpm in 5th vibrates pretty bad, a little in 4th, but clears up at about 2600. I'm pretty sure mine is in the trans.

[smax]

I had the same issue and found that it was in my tune. I had a lean spot that was causing a vibration that felt a lot like really bad clutch chatter.