....

 

A quick reminder for the newly-arrived: Curt put in some 'emergency motor mounts' and he reported that they had no effect on the vibration. And thus why MM's have moved lower on the suspect list.

Curt, I'll fully process your addition posts and respond .... tomorrow probably.

 

...

 

FWIW, I think I just diagnosed my odd intermittent drivetrain vibration and occasional noise on 86 USA automatic.

It is something you should consider at least since yours is aitomatic. Long shot. But I didn't see it mentioned.

Inside the TC cover there is a pair of large bearings that carry the stub shaft, essentially the drive shaft at that point. I thought one was bad. Noise was from there. With me under car listening. Didn't even need the stethoscope.


Between them is a spacer sleeve. I would have thought it would be pinned in between the two bearing inner races, spin with them, same speed as shaft. But It is worn inside. Has spin marks. Shiny. Both inside and on its edges where it contacts the two bearings. Its obviously able to waggle a little bit and contact the driveshaft, not pinned between bearings, so it can change speed and occasionally drag.

Guess I need a new one.

You might consider checking yours.

 

Chris - Do you think the play and wiggle or binding is due to wear alone - where a new one would fit snug as you described?

 

I've read-through the last ~36 hours of posts. Everything still seems consistent with an issue with the front right suspension. More on that in a minute...

There's still the possibility that the motor-mounts are the 'instigator.' Stan's recommendation that you take a close look at the 'fingers' on the MM bracket and bottom plate is a good one. The 'emergency' mounts you tested with won't rule out a vibration caused by the fingers coming into contact when the motor shifts on the mounts.. because the 'emergency' mounts will put the fingers closer together. You might be able to use a flashlight and inspection mirror to find witness marks.

Now, back to the suspension. Here's what I would do:
1) get a helper to sit in the driver's seat.
2) lift the car on your four post (not the two-post) so that you can get under it.
3) for each of the 8 suspension joints, have your helper cycle the steering wheel back-and-forth(*) at about a 0.5 Hz rate or whatever slow rate allows you to get a good visual of the movement of each joint.
4) for each of the joints watch it carefully as it's being loaded and unloaded and look for incorrect movement(**).

You want the suspension loaded for this test and thus the four-post. When the suspension is unloaded you've got too little resistance to motion to find anything other than 'about-to-break' wear.

(*) The goal isn't to actually turn the wheels, but to put load on the suspension joints. For the tie rods you don't need the wheels to move. For the upper and lower ball joints, a little movement of the wheel may be helpful if the static loading/unloading of the joints doesn't provoke any movement (as-designed movement or otherwise.)

(**) You know how each of the joints should behave if in perfect condition: ball joints are free to rotate but should never translate on any axis. Any translation movement you see is an indication of serious wear.

The "Six Million Dollar Cat" is doing phenomenally well. Thanks for asking.

 

This is a hard test to do without changing the weight distribution on the front right. If you can, with some certainty, say that the weight transfer on the right side of the car was more-or-less the same in both gears then it points to engine-speed or engine-load.

When I drove your car, did it come off of the two post or the four post? Or, in other words, when I drove it was the suspension settled? Or did I setting the suspension while driving? I don't recall. However, I do recall that the general behavior of increasing vibration in a left turn wasn't too dependent upon road speed or engine speed. We did go up and down on I-87 to do some 'at speed' tests.

 

One way to easily reveal witness marks is black spray paint where you expect to see them. It's worked well for me - either ruling out a suspect area or made it very obvious where the contact was happening.

 

I was not hard on the throttle as I shifted to 4th and back, just maintaining speed, on the level, about 48 mph. Nothing subtle about the difference - I'm trusting my observation in this case.

The car had been on the two-post lift before you drove it.

I tried to focus last time out on this less specific vibration you were feeling. If there was any, I could not distinguish it from "normal", from road surface irregularities.

The mounts are kinda buried in there, it would be hard to spray them I think. But I do need some method - thanks.

The heat has put me in a low-energy mode. Instead of being confused about this vibration, I'm laying around, reading a book titled "What is Real? The unfinished quest for the meaning of quantum physics." Even more confusing.

But I did manage to plan an experiment that should be definitive on whether engine twist or lean has anything to do with it. I'll try it out in the morning. I'll drive until the vibration comes on, then put it in (with lots of duct tape to keep it from shaking loose).



Thanks, everyone. Have a great 4th.

 

Ok, as promised I performed my upper engine brace test. Like before, there was initially no vibration (the 2100 rpm sort) but it gradually re-appeared. Then I put in the contraption and went out again. I thought there were three possibilities: 1) a natural 2100 rpm vibration of the engine would be felt more strongly because of this brace, 2) the vibration would be reduced if the engine flopping right in a left turn was bringing something in contact at the engine mounts (maybe transmission mounts, or elsewhere), or 3) no change.

The result was 3) no change. I was hoping for 2.

It's still possible that some purely lateral motion in the mounts (or elsewhere) is causing contact, or there was a flaw in the experiment (I had to use judgment for setting the preload of the brace). But next up: Dave's suggestion to manipulate the suspension and steering bits, under load. I wonder if I should put something under the tires, so they don't get stuck on the abrasive surface of the lift runways.




====

Finished the book on quantum mechanics, but was disappointed to learn that the fundamental issues of non-locality and the "measurement problem" are still unresolved. I see parallels...

 

 

To account for all observations, the "theory of everything" for my car's vibration must include something related to engine speed (a vibration with which there is a resonance at 2100 rpm, felt or not felt according to inertial forces, mostly from turning left), and something unrelated to engine speed, varying in a manner suggesting something in the front suspension. I've only felt the first, while Dave has only felt the second. Could they be related? I have no idea.

After replacing an obviously loose tie rod and tightening up the front bearings, the second vibration might be gone for all I know. But I ought to be able to feel looseness, so I'll continue down that track.

Taking the results of my experiments altering the way the engine is supported at face value, the vibration does not involve intermittent contact at the engine end of the drivetrain. I'm going to put a strap on the transmission to discourage it from shifting to the right. Recall that I changed the transmission mounts during the TT job.

I'm going to ponder taping a microphone to places of interest - I think I have the necessary items, but 2100 rpm is 35 Hz. Not quite desperate enough to risk an iPhone.

My concrete guys are coming this week to pour an apron for the garage, so the car will be trapped inside for a few days.

 

Besides the tc bearing spacer anomaly, I've experienced one other weird situation worth mentioning.

Partially blocked injector. Behaved differently on start making right turn vs left. Was pretty acute, with very rough running vs very smooth. All I'm saying is perhaps there is an injector pattern change intermittently for you car under certain conditions.

Throwing wear parts at a problem is a weaker methodology than real diagnostics that Greg, Sean, Dave and others utilize. But I'm also still hanging in here after x years do it can't be the worst approach. Close, perhaps.