Bad vibrations (Part 2!)

[miller]

Expert? Me???

 

[Dave145]

Yes when I try to push the engine out of the car it takes the car with it.

 

[moper]

Looking at the pictures you posted - the engine is crooked, and whether or not you feel it is causing an issue, it's not "normal wear and tear" the car might deal with. My suggestion would be to loosen the mounts at the K frame, and loosen the two bolts on the trans mount. Then straighten it out and re-test. You want it to be level too. I like to measure up to the block from the centerlink. That's fairly parallel with the plane a line drawn through the two engine mounts should be in. I think if you do that, your vibration will go away.

 

[Dave145]

I do agree that it looks crooked as all hell. It's even more obvious when you look at the trans flange from the rear axle. The driveshaft is on a real steep angle between the trans and the rear end because the trans is cocked sideways.

Tonight I will try loosening everything tonight and see if I can get it straightened out. Optimally it'll easily come right into line.

I really gotta wonder how the hell it got so crooked.

 

[Paul_G]

I really gotta wonder how the hell it got so crooked.

The engine and trans are sitting on rubber mounts. Rubber degrades over time. The weight of the engine and the trans along with the stress placed on the rubber mounts has taken its toll. You have to get the driveline back in proper alignment. I know you want to stop spending but you can't fix it for free. Parts cost money.

 

[Ski 61701]

I do agree that it looks crooked as all hell. It's even more obvious when you look at the trans flange from the rear axle. The driveshaft is on a real steep angle between the trans and the rear end because the trans is cocked sideways.

Tonight I will try loosening everything tonight and see if I can get it straightened out. Optimally it'll easily come right into line.

I really gotta wonder how the hell it got so crooked.

Someone put the motor mounts in wrong

 

[threewood]

Has the car always had a vibration?
When you get to 70 or where it vibrates have you tried putting it in neutral to see if it has an effect?
You said you cannot replicate the vibration with the rear on jacket stands and in drive?

 

[miller]

Someone put the motor mounts in wrong

Do you have a service manual for the car? Should show how all three mounts are set in place. Guess anything is possible, especially with what your dealing with.
Don't see it, if they have never been changed...60 years old.

 

[Dave145]

I got the motor and trans to sit straight in the car last night by loosening all three of the mounts and pulling it over to the passenger side. It didn't need to move much, but it is most certainly in the hole straight now. I also put a bubble level on the trans and on theotor to make sure everybody is level. Took it out for a drive and didn't notice much of a change.

I came home and pulled the 4° shims out of the rear axle. I also let all the air out of my air shocks. Took it for a drive. Seems a tad better. I can get to 65 now with only a bit of a shimmy.

Came home refilled the shocks. Added 65lbs of air to them. Took for another drive. Same as test 2.

I also measured the rear end to make sure it's centered in the car, and it is. The trans is centered in the tunnel as well. Eyeballing the driveshaft from the pinion to the trans sure looks like it is straight as an arrow.

Tonight I am going to try swapping in the old driveshaft, as well as trying my second set of tires again. This will allow me to pinpoint whether the tires and driveshaft have any effect on this issue.

If the issue still persists (like I'm betting it will), I guess the next test is to put it up on stands and run it with and without the driveshaft up to speed and see what happens.

The car has had this issue ever since I bought it. When at speed I can shift it into 2nd and neutral with no change in the vibration at all. Also while on the highway I've tried accelerating, decelerating, cruising, rocking the steering wheel side to side as well as tapping the brakes while coasting to see if any of that would change the problem. It definitely doesn't.

 

[Glenwood]

One single change may not eliminate the issue but I think you're on the right track.

 

[Dave145]

I'm doubting it'll be just one thing that'll fix this issue as well. Just figure that at least by eliminating basically all of the variables and isolating the big components (engine/trans and rear end) that I'll be able to better narrow down where the issue may be eminating from.

 

[Dave145]

I also forgot to add that last night I retested all the mounts. With everything bolted up, I put the jack under the tailshaft of the trans and lifted. It pretty much takes the car up with it immediately. While I had it loaded, I checked it with a light and a mirror looking for cracks and I couldn't find any.

I then put my jack under the harmonic balancer. Again while lifting the motor up, the car came with it. With the mounts loaded I checked for cracks, and couldn't see any with my light and mirror.

I set the motor back down and measured the compressed area of the rubber on the motor mounts. Both mounts measure 1.25" tall on the compressed part of the rubber. To me, this measurement tells me they are loaded equally. The fact that the motor sits level front to back as well as side to side makes me believe the mounts are still okay...correct?

I'm not saying the mounts aren't the problem. They very well could be, and the data I've gathered so far could just be a coincidence. Nothing is really off the table here as far as problem and solutions go, but at least by measuring and testing everything we can see what does and doesn't have an effect on this problem.

 

[5.7 hemi]

Uh, don’t ever jack the engine up by the balancer, damn good way to bend the crank.

Looks as though your getting stuff narrowed down.

 

[Dave145]

Good to know. Pretty much took my dad's advice on that one. He's been doing this for a good while, but yeah I agree now that I think about it. Last thing I need is something else to get bent or broken!

 

[Fran Blacker]

Good to know. Pretty much took my dad's advice on that one. He's been doing this for a good while, but yeah I agree now that I think about it. Last thing I need is something else to get bent or broken!

Dave have you determined if there is a ball or needle bearing or a bushing in tailshaft of trans? My tailshaft bushing was only worn .015 or so an it rattled bad at 3000 rpm. I took it out this weekend for first time after replacement , 3500 rpm no rattle. .015 isn't much movement but at speed.... While you have d shaft out take another look.
I'm a little hung up on the bearing/bushing diagnosis.

 

[Dave145]

I have seen parts listings for a bearing and a bushing, so I'm not sure exactly what it has. I don't have a service manual for the car so I can't even look at that to determine what's in there. While the shaft is out tonight I will try to wiggle the shaft around to check for play.

 

[Dave145]

Alright everyone I'm back. Last night was an eye opener. Here's the tests and results.

First tried the old driveshaft. Seemed a tad less harsh, may have just been optimism. Still shook at 65-70.

Then tried old driveshaft with 2nd set of tires. Vibrated even worse this time, probably because the tires are a good bit smaller than my current ones (185/70r14 vs 225/70r14).

Came home. Put my 225's on it again and jacked up the rear end. With the car on stands, I started the car and put it in drive. Everything seemed okay at low speed. Rock solid, no shakes. Then I had an assistant take the gas pedal while I watched everything. Assistant ran the car up to 50mph on stands first. Everything was solid. My rear end is an open 2.76, so only the driver's rear tire spun. Driveshaft had no wobbles or oddities, trans flange and pinion yoke were solid as well. Cool!

Had my assistant push it up to 75mph. Now the trouble starts. The driver's rear wheel continued to spin true. The driveshaft and driveline spun perfectly. But the shake started. The passenger wheel, which had been dormant this whole time, began to shake violently, as did the body of the car. During this time, the helicopter sound was again present. Had my assistant let off the gas, only to hear a loud whirring noise come from the rear end.

Looks like something ain't right back there. I already know the passenger rear wheel usually spins first, so it's odd that that's not the case. When I got the car initally, I had to dump in a bottle and a half of diff fluid before the rear end was full.

My guess is that the bearings are shot in the center section. I've had a number of people suggest that I may have a bent axle/axle tube.

 

[the mississippi madman]

I'm glad we finally narrowed it down to a particular section of the car

 

[5.7 hemi]

Pull it apart. Take pics!

 

[Dave145]

As am I. Now the rear question is am I looking at needing a center section or a whole axle? The tubes don't appear to be obviously bent, but being that all the axle stops have been smashed leads me to believe this car was at some point bottomed out.