Gear Mesh That Becomes Tornado Siren - Team Camaro Tech
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post #1 of 8 (permalink) Old May 29th, 13, 07:42 PM Thread Starter
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Exclamation Gear Mesh That Becomes Tornado Siren

Hey all, now that I have your interest...

This is that same 91 Z28 that was giving me starting/running fits just a few short months ago (I love my wife!..err, I mean, I love this car, really babe, no problem, we'll figure it out)
It's a 5.0, 5-speed, with 198K miles on it. (just gettin her broke in)

So we've got the car running great, she drives it to work every day with no troubles. A few days ago I happened to ride with her somewhere and was almost deafened by the whirring sound coming from behind me and underneath somewhere. In first gear it sounds exactly what I would expect a diff with no lube in it to sound like. By 50 mph it sounds like a tornado siren is going off in the back seat!

I promptly checked the diff for fluid and it was surprisingly quite full. I intend to go ahead and replace the lube in it because after 198k that can't be a bad idea. But are there any other issues I should look at that might be obvious to ya'll? I intend to visually inspect both ends of the driveshaft...any other thoughts?

I've asked her not to drive it more than into town (work is about 20 miles one way) so she's a little antsy to get this fixed!

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post #2 of 8 (permalink) Old May 29th, 13, 07:49 PM Thread Starter
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Re: Gear Mesh That Becomes Tornado Siren

I should also add that I had her drive by me on our road and much to my surprise I couldn't hear the sound from outside. So whatever it is seems to be resonating from somewhere inside the car, which also makes me wonder if the apparent point of origin is not actually where the source is...
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post #3 of 8 (permalink) Old May 29th, 13, 08:03 PM
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Re: Gear Mesh That Becomes Tornado Siren

Check the trans oil level?
Maybe sit in the back seat and listen?
Did a previous owner install a gear drive for the camshaft vice a chain?

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post #4 of 8 (permalink) Old May 30th, 13, 06:14 AM
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Re: Gear Mesh That Becomes Tornado Siren

3rd and 4th gen Camaros are some of the worst for rear end noise, the have the torque arm up to the trans, transferes the noise up front, make sure you have good rubber in the front torque arm mount.
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post #5 of 8 (permalink) Old Jun 3rd, 13, 12:28 PM
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Re: Gear Mesh That Becomes Tornado Siren

Just an idea, only because I had this issue once, but check the pinion nut. I had a sound coming from the rear underside of my Z about 500 miles after I installed a 12 bolt back in it. It was recently rebuilt with 4.10's by PO. I was on my way home from a car show and was about 4 miles away and I started to here this whirling sound. I had no idea what it was, pretty loud and windy sounding. I came to a stop, listened to the engine, heard nothing and let out the clutch and started to here it again as I gained some speed. I was just about home then, limping it all the rest of the way. Next morning I went under the rear and grabbed the driveshaft and gave it a twist and noticed the yoke was wobbling. Pulled the driveshaft and found the pinion nut was half way unscrewed. PO must have forgot to torque the nut. Had to pull the rear and take it to a friend of mine to check it out and all was good. No damage to ring or pinion, put in a new crush sleeve and torqued the nut and that was it. Sound gone. However those Richmond 4.10's were noisy as hell. Sounds like a truck inside the car.

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post #6 of 8 (permalink) Old Jun 9th, 13, 07:48 AM Thread Starter
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Re: Gear Mesh That Becomes Tornado Siren

So I did find that the trans is low. The label indicates "Use Dexron II", which I believe should be something else now, but what are the thoughts on what that something else should be?
Dexron VI? Dexron III?
How important is it to drain what is in there first?
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post #7 of 8 (permalink) Old Jun 10th, 13, 12:45 PM Thread Starter
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Re: Gear Mesh That Becomes Tornado Siren

Listed the car to starboard to drain the oil (and sucked out all I could that wouldn't drain by itself), then listed it to port to fill it with 2.96 qts of Dexron VI. Went with the Valvoline fully synthetic. Noticeable (not dramatic) shifting improvement, but no affect on the gear whine! Next will be replacing the gear lube in the rear diff, and while I have the old stuff drained out I intend to pull the cover off and really get a look inside.
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post #8 of 8 (permalink) Old Aug 28th, 13, 11:54 AM Thread Starter
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Re: Gear Mesh That Becomes Tornado Siren

Long delay, but the problem does have resolution!
The issue turned out to be the front pinion bearing. Significant pitting on both the bearing and the cup. The rear had no pitting, but it did have some RTV coming out of the bearing like a hernia...??
Replaced both the front and rear pinion bearings and cups with new Timken units, new seals on the axles but did not replace the carrier bearings because they really looked perfect. Put it all back together and my wife's description was "it's stealthy!".
Since we had it apart anyway, we also replaced the stock driveshaft with an aluminum shaft that came with the car when we bought it. The previous owner just never got around to exchanging it.
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