Freddie's Back on the Road!

**MacDee** · January 13th, 2015, 11:54 AM

Originally Posted by Luva65wagon

Same U-joints? Maybe all this new "Saturn 5" launch torque has made one of them fail? They would vary with load as well.

What's the frequency?

Originally Posted by Jeff W

I carefully read your posts again and can't see the specifics...

Do you FEEL anything or is it strictly "noise". I know it's hard to tell the difference sometimes.

It is definitely FELT, but it acts like an acoustic dissonance.

While cruising along at about 50 mph, there is a vibration that sort of grows and subsides, grows and subsides, over and over, continuously, at about 1 cycle per second. If I feed a little more throttle, as when going up a slight grade, the frequency of the vibration rise-and-fall cycle will increase to... I dunno... 3 or 4 cycles per second without any significant change in road speed.

This is why I'm suspecting it has something to do with the torque converter. The torque converter has within it a Stator and a Turbine which spin on a common axis, one driving the other. Because of slippage, their relative speeds will always be slightly different. However, the more load you have, the more speed difference there will be between the Turbine and the Stator. I'm not sure, exactly, how this relates to the vibration, but it's the only thing I can think of that would have two components spinning out-of-synch. Maybe the converter isn't quite centered on the flex plate so the turbine is slightly off-center?

Or am I just over-thinking this...?

I'm going to take Randy Long for a ride. It will be up to him to fix it!

**Luva65wagon** · January 13th, 2015, 12:37 PM

I have a very similar harmonic vibration post V8/C4 install in the Flarechero. A part of me thinks it is drive-line angle issues, which I never checked.

Shouldn't be an issue for you with the stock components, but I had to rig a lot of mounts to get that thing shoe-horned in. I saw in a CarCraft article a phone app available to do that. Someday, when I have a flat surface available to me again.

http://www.hotrod.com/how-to/additio...le-finder-app/

But u-joints failing can do exactly what you are describing.

Not that the torque converter couldn't also be failing - it is all but impossible to install incorrectly. The only way I've ever seen an install failure is when there is a drain-plug on the converter that doesn't find its way into a hole drilled into the flexplate. The converter has a lead-in to the crank that centers it.

**Jeff W** · January 13th, 2015, 03:02 PM

Can you remind me, does your dual exhaust have a cross-over?

I think you are getting some kind of harmonic pulsar thing caused by coincidental chamber sizes of your mufflers and the distance to your crossover pipe.

Too wacky?

**MacDee** · January 16th, 2015, 11:24 AM

Originally Posted by Jeff W

Can you remind me, does your dual exhaust have a cross-over?

I think you are getting some kind of harmonic pulsar thing caused by coincidental chamber sizes of your mufflers and the distance to your crossover pipe.

Too wacky?

Yeah, I think you're wacky....

Exhaust does have a cross-over via an x-pipe arrangement. The pipes come together just downstream of the header outlets before going off on their separate routes back to the mufflers.
I'm sure that's not it, though. It didn't do this before the rebuild!

Besides, I think you're just yanking my chain.

**Luva65wagon** · January 16th, 2015, 12:02 PM

Jeff would never do that.

**Jeff W** · January 16th, 2015, 04:16 PM

Originally Posted by MacDee

I'm sure that's not it, though. It didn't do this before the rebuild!

Besides, I think you're just yanking my chain.

I am being thoughtful and thinking outside of the box. Your engine is breathing better now than before and with different valve timing. Don't underestimate the power of air and harmonics. I can drive all over at any speed in my van with the windows down without problem. When we are in the CRV and crack a window, between 45 MPH and 55 MPH the pulsing drives me bonkers. Drive faster or slower, or open a second window, and all is fine.

Without experiencing the sound myself, hard to narrow in. Maybe you need to offer rides around the block

Here is a little physics discussion that is interesting:

https://www.physicsforums.com/thread...monics.475510/

**pbrown** · January 16th, 2015, 09:45 PM

Pull the drive shaft and have it checked. Maybe it got bent or banged up or something while the engine was out. I also seem to recall that it was a little on the short side.

**MacDee** · January 17th, 2015, 09:34 AM

Originally Posted by Jeff W

I am being thoughtful ...

Here is a little physics discussion that is interesting:

https://www.physicsforums.com/thread...monics.475510/

Very interesting... A new exhaust system is at the top of my list anyway!

Originally Posted by pbrown

Pull the drive shaft and have it checked. Maybe it got bent or banged up or something while the engine was out. I also seem to recall that it was a little on the short side.

You remember correctly. The shaft is a bit too short. Maybe I've just been lucky and my luck has run out!

I took Randy for a ride, and he seems to be suspecting wheel bearings. I can't recall if we replaced them at the time of the disc brake conversion, or just repacked them.

**Jeff W** · January 17th, 2015, 10:55 AM

Originally Posted by MacDee

Very interesting... A new exhaust system is at the top of my list anyway!

You remember correctly. The shaft is a bit too short. Maybe I've just been lucky and my luck has run out!

you may remember that I have a driveshaft for your layout (C4 with little rear). You are welcome to borrow it for troubleshooting. I can bring it to the meeting next week.

**MacDee** · January 20th, 2015, 01:31 PM

Originally Posted by Jeff W

you may remember that I have a driveshaft for your layout (C4 with little rear). You are welcome to borrow it for troubleshooting. I can bring it to the meeting next week.

I DO remember that you have that driveshaft! As I recall, its u-joint to u-joint length is 52 5/8 inches, which is 5/8 inch longer than mine.

I may, or may not, be at the meeting. If you happen to have the driveshaft with you, and I happen to also be at the meeting, I may or may not take you up on your offer.
How's THAT for decisive!!

**Jeff W** · January 20th, 2015, 07:31 PM

Almost enough of a reason for me to dig it out of the storage slot and load it up.

I thought it was 52 - 1/2... I can check if that helps.

**MacDee** · January 21st, 2015, 09:04 AM

Plans have firmed up...
I will be at the meeting tonight, but I will NOT take your driveshaft. Freddie's going back to Long's next week for new wheel bearings AND to get her driveshaft lengthened and u-joints checked/renewed.

Thank you for the offer, anyway!

**MacDee** · March 17th, 2015, 11:33 AM

Randy Long has tried tracing my vibration problem, and we have renewed several things along the way: Wheel Bearings, Axle Bearings, Rear Brakes.... Several things have been checked and ruled out: driveshaft/u-joints, torque converter.
He has run the car, in gear, up on a lift and traced the vibration along the entire drive train with a stethoscope. The only thing left to check now is the engine itself.

To do that, he wants to run the engine without the torque converter or trans hooked up. And to do THAT, he need to bolt up a FLYWHEEL.

He can't find one....

Does anyone out there have a FLYWHEEL for a 200 six that I could... BORROW?

**Luva65wagon** · March 17th, 2015, 11:38 AM

I do... would you like me to bring it to the meeting tomorrow?

**SmithKid** · March 17th, 2015, 12:54 PM

Is a bare flywheel going to be heavy enough without the added weight of disc/pressure plate? I remember back in flywheel weighting/lightening days that a little weight loss off the flywheel produced noticeable vibration in order to gain a faster revving engine. Of course, that was on 2 cycle motorcycle engines, and I actually added weight to a crazy-revving Suzuki 400 to smooth it out.