Need help finding subframe noise - Team Camaro Tech
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post #1 of 10 (permalink) Old Dec 14th, 18, 12:46 AM Thread Starter
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Steve
 
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Need help finding subframe noise

I have a modified 67 RS convertible. Bored and stroked SBC 350. Tremec 5 speed trans with hydraulic clutch. 373 12 bolt posi rear. Subframe extenders. Poly bushings on front suspension and subframe bushings. Complete frame off restoration completed in 2007. Exhaust system new 2 weeks ago.



My problem: When I drive over a dip in the road surface (reverse speed bump) I get aloud cracking sound. It can be felt on the shift lever. I feels like the tranny has been struck by a sledge hammer.



I would appreciate any suggestions. Thank you. Steve
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post #2 of 10 (permalink) Old Dec 14th, 18, 04:12 AM
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These things can be difficult to diagnose. I’m going to guess here, could your driveshaft be too long????

1969 X66 396 LeMans Blue, M20, 373 (Sold)
1969 Convertible LS3 TKO 600, 373
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post #3 of 10 (permalink) Old Dec 14th, 18, 04:19 AM
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Re: Need help finding subframe noise

Are you saying that this is new since the exhaust system was worked on and you need to hit the dip squarely to make this happen or that this has been going on since 2007 and it happens if you just drop one wheel?

67RSSS......owned since 69. A basket case for most of it.
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post #4 of 10 (permalink) Old Dec 14th, 18, 04:23 AM Thread Starter
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Re: Need help finding subframe noise

Thanks for your reply. We had ds shortened when installing Tremec. Drive shaft length seems very plausible. It would hammer the tran. Thanks, we will check this carefully.
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post #5 of 10 (permalink) Old Dec 14th, 18, 04:26 AM
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Quote:
Originally Posted by slakis View Post
Thanks for your reply. We had ds shortened when installing Tremec. Drive shaft length seems very plausible. It would hammer the tran. Thanks, we will check this carefully.
Absolutely!!

1969 X66 396 LeMans Blue, M20, 373 (Sold)
1969 Convertible LS3 TKO 600, 373
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post #6 of 10 (permalink) Old Dec 14th, 18, 04:58 AM
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Re: Need help finding subframe noise

When you measured for the new driveshaft was the car on the ground sitting at ride height? Is the car lowered?

Don

1969 Camaro LSA 6L90E AME subframe and IRS
1969 Camaro vert LS3 4L65E Ridetech level 2 - sold
1959 El Camino project
1969 Mustang Sportsroof project
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Last edited by dhutton; Dec 14th, 18 at 06:27 AM.
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post #7 of 10 (permalink) Old Dec 14th, 18, 10:10 AM Thread Starter
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Steve
 
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Re: Need help finding subframe noise

I had a cracking sound after the 2007 restoration. Traced that to drivers door hitting sill plates. Restorer corrected the problem. (The trans didn't feel like it was hit with hammer).

I think this began after we installed Tremec 5sp. Both front wheels have to hit dip at same time. No noise when only one of the wheels crosses rut.

Drive shaft was measured on level shop floor.

The car is lowered. We went over the entire under carriage there seems to be nothing solid can hit the subframe or trans. We replaced engine mounts with taller mounts, to be sure.

I think that the most logical thing is that the drive shaft was mismeasured. Drive shaft spline slamming into trans would feel like a hammer hit trans.

The Camaro was a plain jane six with a four speed. I wanted a car that looked old but handled like a modern car. It has done that for me. I can drive on NJ turnpike at 80mph with engine rpms in low 2000s. And also safely drive on winding back roads.

Thanks for your replies. This spring I will let you know the results. Thank you and Merry Christmas!
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post #8 of 10 (permalink) Old Dec 14th, 18, 10:15 AM
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Re: Need help finding subframe noise

Steve, I have almost the same exact set-up as you with the exception of an LS3, this is in my 69 vert. Which Hyd. throw out bearing are you using ??

1969 X66 396 LeMans Blue, M20, 373 (Sold)
1969 Convertible LS3 TKO 600, 373
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post #9 of 10 (permalink) Old Dec 15th, 18, 02:05 AM Thread Starter
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Re: Need help finding subframe noise

Purchased Tremec pack from American Power Train. The bearing is their brand Hydromax.
Info available on americanpowertrain.com
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post #10 of 10 (permalink) Old Dec 18th, 18, 04:18 PM
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Re: Need help finding subframe noise

I guess while you are under there, check the trans mount and cross member bolts too

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