Strange rattle/vibration sound

**Gitanesteel** · April 23rd, 2018, 12:10 PM

Ok, so update and looking for some tips/advice for a novice on the best way to check.

I took the Falcon out again this morning. The rattle/noise has been more persistent at slow speeds, especially when accelerating after turning right. However, this morning I also had a lot of drivetrain vibration on accelerating. The transmission seemed to shift gears well enough but there was this shaking from underneath (it seems) on acceleration. It diminished around 50 mph when cruising but any time I pressed on the gas you could feel it again.

My neighbor and I suspect the u-joints are bad. I'm not sure if they were ever replaced when the car was rebuilt. I'm assuming they were. The rear of the car is on jack stands right now.

1) What is the proper way to check the u-joints?

I've got the rear on jack stands. Car is in park. Driveshaft rotates a little side to side on rotation and the wheels move before they stop because of the transmission in park, I assume. On the rear, in tying to manipulate the shaft up and down or side to side there's no movement.

On the front there is a slight amount of movement up and down - not much but definitely not tight like the rear joint. Could this make that vibrating noise since it's at the transmission?

2) Where are folks getting their replacement ones?

Finally, if not the u-joints what else would cause that vibration/shudder - torque converter?

**Gitanesteel** · April 24th, 2018, 07:57 AM

A couple of photos - front and rear view of the driveshaft. The fact that the vibration is more pronounced at lower speeds has me confused.

**Luva65wagon** · April 24th, 2018, 10:55 PM

Hey Scott. If the U-joints are even slightly bound-up you'll get vibration. Maybe even more-so than if they are a little sloppy worn-out.

The only real way to check them is to pull the drive-line out and give them a feel. The front one you just need to pivot the yoke in its two directions to see if it is smooth and not too tight or too loose. Sort of the same with the rear, except the two caps will need to be rotated individually. That said, you may not feel or notice a failure that might be evident only when the car is under load, so I would suggest having them replaced. At $15 a piece (give or take), no point guessing. Whether you do them yourself or you take the shaft somewhere to have them replaced - that's not something I know how best to suggest. You can probably see DIY videos on YouTube if you wanna give it a go.

**Gitanesteel** · May 11th, 2018, 01:34 PM

Well, the mechanic finally drove it and got an initial impression yesterday. Right now he's focused on the torque converter, flex plate or both. He mentioned the potential of a balance issue with the engine but he's going to focus on those two first by dropping the tranny and then running the engine.

He did put his timing light on it and noticed the car was off by a tiny amount so he reset it to the mark where it was initially set when the engine was rebuilt.

Will probably have to wait another week or two before he can dive into it more.

**dhbfaster** · May 16th, 2018, 07:45 PM

Just a note on this...I didn’t know of any problem with my U joints, but when I took them apart during my rebuild I was amazed to find ridges inside there. I was glad I replaced them.

**Gitanesteel** · June 26th, 2018, 10:28 AM

Well, got the bad news/good news today after the engine teardown. Turns out when the engine work was done in 1994 or so on the rebuild a backyard balance job was done and done incorrectly. The crank was not turning smoothly (had an easy and then hard spot in the rotation). Rods were filed at different points, cylinder walls and bearings were scored in places. So, the result is a rebuild - not what I was looking for.

The good news - it'll be a solid rebuild and more reliable than what I had. I decided to go with a 331 stroker kit. Power shouldn't be a big jump over what was already done to the car. I'll also have the block and heads painted black and the valve covers gold to give it the original look while the internals will be upgraded.

Hoping to have it back before the Aug 25th mini-regional.

**Luva65wagon** · June 28th, 2018, 10:24 PM

Well that's a bummer Scott. Good to hear though you've satisfactorily rooted out the problem. A 331 seems to be a popular build and I like the black/gold theme as that is what I've done a couple times as well. Looking forward to seeing it! Fingers crossed I'll make it.

**ew1usnr** · June 29th, 2018, 03:29 PM

Originally Posted by Gitanesteel

Turns out when the engine work was done in 1994 or so on the rebuild a backyard balance job was done and done incorrectly.

Hell, Scott.

How many miles were put on the engine since it was last rebuilt in 1994? Other than the vibration, did the engine show any problems like burning oil or running hot? Was the vibration getting worse? How many more miles do you think that you could have put on the engine if you continued to drive it "as is"?