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-   -   More evidence the driveline ringing is "thermal" (http://www.ssrfanatic.com/forum/f5/more-evidence-driveline-ringing-thermal-5181/)

JimGnitecki 08-14-2005 01:23 PM

More evidence the driveline ringing is "thermal"
 
I have suspected ths beofre, but last evening I got more evidence that the driveline ringing noise I, and some others, have, is related to a thermal expansion effect.

On my way through Alabama last evening, I encountered a very unuually "abrupt" rain storm. By "abrupt", I mean that I could literally see where the road up ahead suddenly turned wet, and sure enough, when I hit that point, the rain was instantly voluminous - no ramp up at all, just sudden downpour!

The same effect occurred on the way OUT of the storm - I could literally see bone dry pavement ahead, and sure enough, when I hit that dry pavement, the rain stopped RIGHT NOW.

What hs this got to do with the driveshaft ringing noise?

Well, at least in my SSR, that noise starts being audible when the vehicle hots about 35 mph and has NOT yet been on the highway at 60 or 70 mph speeds. It goes away after the vehicle has been at those highway speeds for 12 to 15 miles. I have theorized that the sound disappears, or at least becomes inaudible, when the driveline gets HOT.

When I drive through rain, I can't hear the noise even if it is there, because of the noises created by water on the road and rain hitting the top of the vehicle. And, when the rain stops, it normally does so SLOWLY and there is los of residual water on the roads.

The situation last evening was a rare case of the "exception to the rule". Before I hit the rain, I had been traveling more than 150 miles non-stop, so the driveline was hot and there was no audible noise. And yes, the rain and roadspray were loud enough that I could not have heard the nosie if it was there when traveling through the rain.

But, when I hit that abrupt "exit", onto DRY pavement, guess what happened: The nosie was THERE, but only lasted for a few minutes if that, then disappeared again.

My theory is that when I hit the rain, the water splashed up from the road COOLED the driveline. Water is an excellent coolant - that's why we use it in radiators! - and at 60 to 65 mph, there is a LOT of water hitting that driveline when in heavy rain, as I was.

But, when I nsuddenly hit the dry patch, the rain noise and road spray noise disappeared abruptly, but the driveshaft was still cool as a result of the dousing it got in the rainstorm. Therefore, it made noise again until it once again heated up to normal highway temperature.

So, again we have some evidence that supports a thermal effect: the noise disappears as some part (astll unidentified) heats up, because a metal part is slightly BIGGER when hot than when it is cold. The expansion of the part changes the interaction of that part with SOMETHING else, and eliminates the noise.

The question is: what part?

It could be the driveshaft, as that certainly gets a lot of direct exposure to the water in a rainstorm, as a result of road spray under the chassis. However, the entire rear differential housing also gets doused, and the parts inside it would get INDIRECT cooling as a result.

So, we still don't know WHAT is causing the noise. But, each piece of knowledge gets us closer . . . :)

Jim G

beer100 08-14-2005 01:55 PM

me, saying the obvious.
 
The biggest impact would be in the length of the drive shaft.

Another item, which dosen't fit the theory well, is that everything is getting wet. Water by itself could be doing something.

REBEL 08-14-2005 02:06 PM

...
 
Edit ... My mistake, please disregard :banghead

JimGnitecki 08-14-2005 04:31 PM

Rebel: Actually you WOULDN'T know. THink about it! :)

Jim G

Mike in AZ 08-14-2005 05:15 PM

Filled Driveshaft
 
Jim,

I had a 91 4x4 that GM found a way to fix a "ring" or "clink" when it shifted... Right out of the box from the dealership. They drilled two holes in the driveshaft (one at each end) and filled it with expanding foam. This was a factory fix. Oddly enough, it changed the dynamics of the shaft enough to eliminate the sound. The origination of the sound was both the up and down 1st / 2nd tranny shift (automatic) at low speeds. It was especially noisy in low range 4wd. Other inputs excited the drive shaft to ring as well. Before the fix, the mechanical gear change echoed in the driveshaft and was audible in the cab. After..... nothing. I continued to put 120,000 miles on the truck and NEVER had any drive line or tranny issues.

I know it is not the same, but offering my 2c worth of historical input.....

Regards,

Mike

beer100 08-14-2005 05:16 PM

Me :lol

Al Corelli 08-14-2005 07:41 PM

Why not just slot windows on both ends of the shaft, put seals and bearings on each side of each slot, then around each set of bearings put a banjo housing with an attachment for radiator hoses. Then plumb the lower radiator hose through there. The driveshaft will have a different mass, and would also help with cooling.

OK OK, so the shaft would be weaker due to the windows. I tried..

:)

JimGnitecki 08-14-2005 09:31 PM

Mikem2005: I can't figure out how to do what you suggest with cold and hot water while the SSR is in motion on the road!

We think alike though, I DID try filling the shaft with foam when I had GM's number 2 design shaft (current version is number 3). It HELPED but did not do enough. By the way, the mechaniam there is that the foam simply absorbs some of the sound.

Foaming the shaft also requires cutting the ends off and then wlding them back on after the foam fill. The reason is that you cannot get proper foam distribution via just injecting the foam through a couple of holes. You need the ends compltely open to get it right. The rewelding can sometimes be of lesser quality than the factory weld, and that's an issue as it weakens a shaft transmitting 300 to 390 horsepower.

Jim G

Mike in AZ 08-14-2005 09:50 PM

Jim,

Hot and cold water was not my suggestion.... That belongs to rebel.

I looked at some old threads on this and can't make much sense of it all. For all of us newcomers, can you summarize in a few sentences? What are the symptoms like and how do they manifest into something that has to be worked by the dealer? If this is a systemic issue, maybe we all should be looking for it and driving our dealers nuts.

Mike

P.S. Got some top down time today (woo hoo) :) and discovered a slight body/windsheild shake at about 60 that seemed to disappear at 65 and above. I'm guessng this is normal. Comment, Jim?

41chevcoe 08-14-2005 09:58 PM

Quote:

Originally Posted by REBEL
My thought was if cold water brought the tink back, and you tried a hot shaft with hot water and the tink did not come back then the temp was more likely.

I think they are talking gear howl or whine (probably aftermarket gears) at a certain speed, not the tink when putting in gear and/or just starting to move.

JimGnitecki 08-15-2005 06:31 AM

Correct. We are discussing driveline nosie OTHER THAN the "tink".

The noise we are describing specifically is sometimes incorrectly called a "whine" (implying that its source is the ring and pinion in the rear axle), but it is actually more of a "ringing" - like a metallic part that is virating at high freqeuncy as a result of some excitation.

Mikem2005: That shaling you felt at 60 that was gone by 65 is another manisfestation of the same issue I believe. The fact that it peaks at some speeds and attentuates at others implies a resonance effect. Resonance, a repetitive vibration that is amplified by a perfect match between frequency of vibration and some external input force, can result in sound or vibration or both.

If you check pstings very carefully, you will see that both unusual sounds and virbations or shakes have been reported sproadically.

Research continues.

Jim G


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