Tempt Fate 928

I have an '84 auto with two TT bearings. I've been working through Dwayne's wonderful guide to replacing TT bearings and,starting assembly, I'm wondering about omitting the TT damper weight. I've read that Porsche actually delayed the 928 over excessive drive train vibration but apparently Club Sport models went without. I imagine that tossing it will let me beat a Tesla in the quarter and top 50 mpg but,seriously, I do worry about 8 pounds of iron smashing back and forth. Is there any consensus on this?
Thank you

soontobered84

Search can be your friend.

Seriously, there are at least two differing opinions on this very subject just discussed within the last two weeks. Read up on those opinions and then formulate your plan of action.

Constantine

Your 1984 928 torque tube should have three bearing units in there, not just two. Is this a previously rebuilt TT?

As far as the vibration dampener, suggest you keep it in there especially with just two TT bearings in it.

The Club Sport models you referenced are 5- speeds, and all 5-speed models came with three bearing units in their TTs which help mitigate some drive line vibrations.

Greg Brown of Precision Motorwerks sells refurbished vibration dampeners for a good price.

HTH,
Constantine

Mark Anderson

We will have new dampener rubbers available shortly

Mark Anderson

As to your question about weight there are a few different versions with different weights

GregBBRD

This is the best solution!

GregBBRD

There's a plethora of information about the process of building torque tubes, in this picture.

Note the different frequencies written on the different weights. And note that there are different degrees written on each tag. Finally, note that these tags are located on the inside of the weight....between the weight and the torque tube, itself.

So, what does this mean?

It means that each and every torque tube shaft was spun, almost certainly under load.

Once the frequency and the location was known, a specific weight was installed.

Tempt Fate 928

Wow. I'd thought that I was up to speed on this. If Mark Anderson and Constantine say keep the damper then I would be wise to pay attention. There is no evidence that the TT has ever been apart before and no indication of a third bearing. Would a good solution be 3 of Constantine's super bearings?

skpyle

Greg, is this better than your process to rebush the weight? I have the weight from the Red Witch boxed up and was going to ship it to Mary in the morning. Would it be better if I wait and source the rubbers from Mark when they are available?

OP, sorry to butt into your thread.

GregBBRD

If the rubber pieces that Mark is having made work, there will be no need for me to modify anyone's weight, any longer.

Constantine

If you are using the original bearing units, then you should use a dampener.

If you are using Super Bearings, the dampener does not have to be re-used since three Super Bearings replace the need for an extra vibration dampener.

However, others think differently.

Cheers.

GregBBRD

A bit of logic goes a long way, when dealing with the "geniuses" on the Internet and their ideas of what is correct.

Porsche did everything they could do to decrease the weight of the 928. Magnesium intake, valve covers, aluminum fenders, hood, and doors.
Anyone rationally imagine that they added 8+ pounds to the torque tube because they felt the need to randomly add weight?

Like I've been saying for the last 20+ years.....never, never, never leave the frequency absorber out.
It's an essential part of the torque tube assembly.

GregBBRD

Unfortunately, you can't just "wish" things to be true.

It would be great if you would/could gather some data to prove your theory....
or get anyone that knows anything about frequency absorption to agree with you.

Constantine

Oh Greg, do you think before you post?

Our products have been proven for over 15 years in hundreds of applications in every Porsche that has a torque tube. These have been in stock, power boosted and race applications. If the Super Bearings weren't working as advertised, we wouldn't be selling them, let alone people continuing to buy them. The internet, and especially focused forums such as Rennlist, is/are not forgiving of bad products.

It is interesting that you have been using our products for years without complaint and never raised an issue about the vibration dampener until last year, after we challenged you on your theory about "micro-cracking, twisty, old drive shafts" when you were lauding your just released 300M drive shafts. That thread was so full of inaccuracies I was shocked and is why I challenged you about some of your statements and conclusions. So I get it, Greg Brown will not be challenged and anyone who does will suffer the consequences.

Back on the OP's point, Porsche had to use a device like the vibration dampener since the OE bearing units do just about nothing to quell drive line vibrations. The vibration dampener is just a heavy steel weight suspended in rubber holders which, IMHO, should be viewed as a quick fix to re-engineering the OE bearings as we have done to quell drive line vibrations. Also from what we have seen over the many TTs we have rebuilt, no one will convince us that using only two bearing units in a 928 TT is a good thing. And no one can ignore the disaster the 28mm drive shafts have been in the automatics, another not so brilliant change by Porsche for whatever reason.

GregBBRD

Actually, I think about this stuff all the time. I've got 100's of hours involved in torque tube "science", primarily because it interests me and because it was such a huge problem for Porsche, during the development of the 928. (It's hilarious that you would call the frequency absorber a "quick fix" after Porsche spent years and hundreds of thousands of dollars working on the torque tube harmonic issue.) BTW....I've spent dozens of those hundreds of hours talking to multiple experts in the frequency absorption field.....one of the very best happens to be a member of POC.

I've been a "Porsche Only" mechanic/parts consumer, for over 50 years, now. In that time, I've seen literally dozen of companies offering a "better" product go out of business, over these years....and some were around for many years before the errors of their "theory" reared the ugly truth. Boy do they disappear in one big hurry, when things start breaking.

Here's how development of a product works, in the "non wishing", but "actually engineered" world".
1. You come up with an idea.
2. You build a product.
3. You test that product.

Since the issue, in this case, is frequency absorption, "testing' requires actually measuring the frequencies generated. "Wishing" that they get absorbed doesn't make it true.

Here's a simple test of how much research/testing/thinking you've done:

Why do you suppose that all of the automatic torque tubes have no center bearing?