GregBBRD

Didn't say you were dumb. And as far as being the dumbest, that's reserved for someone else....you're not even close.

Just saying the two things are completely, totally, different.

Ducman82

steering vibration .... maybe...

worf928

Ah! Good. I was about to interpret for Greg. At the risk of being wrong I was planning on writing:

Curt, Greg's not calling you dumb. He's saying your butt-o-meter is untutored.

And, since he's not here, and never will be, I can tell you what Jay told me when we started driving: "Curt's just wAAAAy over-thinking this."

I've spent many hours over the years driving with 928 owners in both left and right seat diagnosing vibration issues. There's a mental art to deconvolving the many input sources (e.g. butt, hands, ears, eyes. i.e. the 'butt-o-meter') into actionable observations that can be used for generating additional tests and hands-on diagnostics.

worf928

Yes. The vibration was also evident through the steering wheel and by sound.

worf928

Ah! I forgot about the second set. I remember that my dubious prediction about the set you pulled from the local Euro was confirmed. And I remember that you ended-up with a good set from Mark.

FredR

Dave,

I understand there is a chap who lives at No 1600 Pennsylvania Avenue who desperately needs your help! Even his wife was wearing a coat the other day with a message on it telling him to go screw himself not that your "free press" was able to decipher that one..

Curt,

Having too much intelligence is a double edged sword. Took me a long time to fathom out that "knowing what you are doing and telling the truth" is suicidal for career prospects! Nowadays, like Melania, I do not care- Maybe she should run for president- I reckon that would do for him!

Adk46

Yikes, I started this second thread on my problem because the first one got heated over the wisdom of omitting a driveline damper. This one is going up in flames, too.

I spent yesterday working on Nancy's Prius; I'm still feeling a little suicidal....

Before I started over-thinking the problem, these were the basics:

1. I pulled my car into the garage and changed the TT and associated items that run at engine-speed.
2. On the first test drive, I noticed a vibration I did not have before.
3. Naturally, this set an observational bias in me that it was probably engine-speed-related. But I was aware of this bias: scientists prefer double-blind experiments for good reason.
4. I still believe at the 2 or 3 sigma level that driving around in 4th gear on the same roads, curves and speeds (below 2100 rpm) did not set off the same vibration I felt and heard in 3rd gear at 2100 rpm. (My bad mood intrudes: why do people say "rpm's"? That drives me nuts - the "r" stands for "revolutions", plural.)
5. Nevertheless, I certainly thought the bad tie rod might be involved - for example, a sympathetic vibration excited by an engine-speed vibration as influenced by many factors that might have gotten changed by the TT job, bringing an exciting frequency in line with a sympathetic frequency. Consider a trumpet's natural frequencies and how the player excites them by buzzing his lips.
6. I could have changed the tie rod before Jay and Dave took their ride, but in the interest of science and entertainment, I did not.

Scientists are in the business of over-thinking things. Einstein was a notorious over-thinker of gravity. Even Newton was content with a falling apple. Could Einstein fix a car? Not likely. I lack experience in automotive mechanics, so thinking is my compensation for that deficiency. Sometimes it works. I solved a problem with my coffee maker this morning, by considering the possibility that I had a bad batch of K-cups that were overwhelming the pump.

I'm still in a bad mood, though.

Captain_Slow

Curt...Einstein also said "Things should be made as simple as possible, but not simpler". Hmmm...maybe save this for Frenzy. Will make a great parking lot challenge session for Stan, Sean, Pete, etc.

worf928

Captain_Slow

Dave - Nah...just the nature of forums and communicating in text. This banter in person would play out so differently...ending with smiles...laughing...and a beer. Patience and time will fix this. My concern is should Curt attempt to drive it to Frenzy before solving this one.

Adk46

worf928

I'm good.

We've got months until Frenzy. In any case, based upon Curt writing that the vibration is 80% reduced, I would not be concerned.

skpyle

Gentlemen, if you are going to tackle this at FRENZY, let me know what specific tools to bring. I will have the support Explorer again.

Adk46

With trepidation, I have this report of a drive I took yesterday, about 12 miles to North Creek and back (Dave knows this road well). This was much longer than the previous test drive.

I went there in 4th gear - didn't notice any vibration. I returned in 3rd gear - observed vibration, much as before - that is, no longer much reduced.

While vibration was present (in a left curve), shifted to 4th - vibration went away. Shifted back to 3rd - vibration returned. Did this twice.

I've since adjusted the bearings. I tightened the nut a bit past where it should go, then backed off to a point where the washers can be shoved around. The right is now OK to my untrained senses. The left still has a little movement and a slight knock to it. Neither move when on the ground, but that must take a lot of force, yes? The locking set screw was buggered up a bit on the right side - someone has been in there before me. I'll take the car out on the same route when it stops raining.

GregBBRD

I'm really sorry you got so upset about my posts. My sincere apologies. I only get involved in these "random issue" threads in order to lend a helping hand to people....there is zero upside, for me....my time spent on 928's is worth hundreds of dollars an hour. I've got no "skin" in this game. I'm just trying to help separate the wheat from the chaff, by adding what I know.

As a scientist, I'd think you'd welcome sound logic over, "Well, Bob says you can do it".

My posts on your torque tube vibration issue were made to help people (and you) understand the complete lack of any data regarding removing the counterweight or even adding the third bearing to a two bearing torque tube. From what I can tell, Porsche had a group of engineers working exclusively on this issue, in the design stage, for over a year.....and then constantly through the 8 years beyond this, right up to the introduction of the 1980 models (when they removed the battery box from the transmission and added the harmonic absorber.)

To think that all they needed to do was to toss in a couple of slightly heavier bearings to eliminate the need for the harmonic absorber is....well....I'll be kind....silly.

Because I'm involved up to my balding head with 928's....they are my life.....my feathers get ruffled (a bit) when someone says I'm not only wrong, but doing the wrong thing, for my clients.

You say what? I think I'm one of the very best 928 shops in the country and you say I'm doing the wrong thing for my clients?

Research, immediately, is required!

So, I've continued trying to get down to the bottom of this "issue". I've contacted some of the best vibration and harmonic experts on the West Coast and discussed this entire torque tube issue. Trust me, if you were upset with me before, you really are not going to like what they have had to say!

My comment, on this thread, was admittedly a bit "tongue in cheek" that you couldn't tell the difference between a chassis vibration and an engine vibration. At best, that would be a bit...slow...and could mean the government should take away your tools. You took this very hard, personally, which was not my desired outcome. Again, my apologies. My point was that you had, from the very first post, indicated that the vibration increased with rpms.....and to suddenly think that the problem was a suspension issue made absolutely zero sense, to me.....as I think you are finding out.

Information and logic are my best tools. I listen carefully to every clue a client can give me....and then try to make sense out of what they had to say. They drive their car, all the time. I drive it very little. Sometimes I drive the car 100 feet to put it on a lift. Other times, when something odd is occurring, I may drive it miles to see what the client is referring to.....especially if the problem is something I don't understand.

Reading from your very first post, it seemed like you were certain your problem started immediately after a torque tube rebuild and was rpm related.

Front suspension issue? Seriously? How can that be rpm related? Seriously?

And every good mechanic knows one of the basics:
If something is suddenly screwed up, go back and review what you just did, before you start looking for something else.

If you haven't done so, find the book "Project 928". Read the section "BasicConsept: The Trannsaxle". (You can find it online.)

I think, as a scientist, you will find this reading.......very interesting......and leave you a bit flabbergasted.

Hundreds of thousands, if not millions, of DM were spent on torque tube harmonics.....think about the companies than couldn't make a "fast shaft" work!

It's pretty absurd to think that simply stuffing a heavier bearing in the rear and tossing away the counterweight is going to work. And you think Porsche left the center bearing out because they ran low on them or "forgot" to put them into thousands of torque tubes? An economy move to save money on bearings?

Come on.....Be logical....There's a horror story going on, here. (I'll start another thread, to go over what I've found out...I don't want to ruin your threads anymore than I already have.)

Again, my apologies for ruining your threads. Just trying to help! And I'm not a scientist....or an English major. I'm just a dumb mechanic trying to do my best. Try to understand and be tolerant.